DECLARATION
We certify that the information presented in this report, except where indicated and
acknowledged, is our original effort and has not been presented before to the best of our
knowledge.
ALEX MUGANE KARUGI
F18/22787/2008
Signature……………………………………………………………………………………
Date…………………………………………………………………………………………...
MBUGUA KAMAU SOLOMON
F18/28245/2009
Signature……………………………………………………………………………………
Date…………………………………………………………………………………………...
This project has been submitted with the approval of the supervisor
Project supervisor: Prof. ODUORI, M. F.
Signature……………………………………………………………………………………
Date of Submission ……………………………………………………………………
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DEDICATION
This is to my father, my mother and my loving sisters for their endless support and
encouragement throughout my undergraduate studies. To the lecturers, department of
Mechanical and Manufacturing Engineering for the knowledge and moral support they have
given me for the last five years. God bless you all.
MbuguaKamau Solomon
To God, my father, mother, and sister who have accorded me with endless support during
my undergraduate studies, to my lecturers in the department of mechanical and
manufacturing engineering for the knowledge they have imparted in me in my undergraduate
studies and from whom I have learnt so much. And to Prof. S.M. Mutuliwho gave us
guidance during my undergraduate studies.
Mugane Alex Karugi
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ACKNOWLEDGEMENTS
We sincerely appreciate Prof.Oduori .F. Moses, our project supervisor and lecturer,
Department of Mechanical and Manufacturing Engineering, University of Nairobi, for his
continued guidance in, and helpful suggestions on the project work. He also provided us with
helpful literature materials.
We thank God for keeping us healthy during the project period and also for insight in what
we were undertaking. Last but not least, to our parents for both financial and moral support.
God bless you all.
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ABSTRACT
Failure of components due to poor selection of materials is a common problem in
engineering. This project addresses these challenges by employing an intensive knowledge
and system approach of information processing to materials selection. The objective of this
project is to develop a materials selection process based on the principles of decision theory.
A case study of wire rope selection will be used to test a computer system developed for the
selection of materials on a wire rope. The critical characteristics of the wire rope material
will be identified and formulated. Selection will be done in two stages: screening followed by
ranking. The first stage reduces the large material database to a small candidate list which is
locally available and meets the critical property limits such as strength. The second stage will
involve ranking the candidate materials using indices formulated from availability, cost and
machinability. Supporting information will then be sought and used to narrow down the
ranked materials to a final choice allowing a definite match to be made between design
requirements and material attributes. This material selection system helps the designer
perform the rigorous process of material selection.
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Contents
DECLARATION................................................................................................................. 1
DEDICATION .................................................................................................................... 2
ACKNOWLEDGEMENTS ................................................................................................ 3
ABSTRACT......................................................................................................................... 4
OBJECTIVES ....................................................................................................................... 7
1
CHAPTER ONE: .......................................................................................................... 8
1.1
INTRODUCTION .................................................................................................. 8
1.1.1
DECISION THEORY ...................................................................................... 8
1.1.2
Kinds of Decision Theory ................................................................................ 8
1.1.3
General Criticism ............................................................................................. 9
1.2
HISTORY ............................................................................................................... 9
1.3 A BRIEF DESCRIPTION OF INFORMATION PROCESSING AS APPLIED TO
A MATERIALS SELECTION CASE STUDY ............................................................... 10
1.4
2
STANDARDS AND CODES ............................................................................... 11
CHAPTER TWO......................................................................................................... 13
2.1 REVIEW OF LITERATURE ON DESIGN, MATERIAL SELECTION AND
MANUFACTURING ...................................................................................................... 13
3
2.1.1
INTRODUCTION ......................................................................................... 13
2.1.2
ENGINEERING DESIGN PROCESS............................................................ 14
2.1.3
MATERIAL SELECTION............................................................................. 17
2.1.4
FACTORS INFLUENCING MATERIAL SELECTION PROCESS .............. 20
2.1.5
MECHANICAL FAILURE MODES ............................................................. 23
2.1.6
PHYSICAL PROPERTIES ............................................................................ 27
2.1.7
MANUFACTURING PROCESS ................................................................... 29
2.1.8
COMMERCIAL PROPERTIES (COST AND AVAILABILITY) .................. 31
2.1.9
REGULATORY PROPERTIES ..................................................................... 32
CHAPTER THREE ..................................................................................................... 33
3.1 LITERATURE REVIEW ON ENGINEERING MATERIALS, THEIR
CATEGORIES AND PROPERTIES. .............................................................................. 33
3.1.1
INTRODUCTION ......................................................................................... 33
3.1.2
ENGINEERING REQUIREMENTS.............................................................. 34
3.1.3
CLASSIFICATION OF MATERIALS .......................................................... 38
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3.1.4
4
METALLIC MATERIALS ............................................................................ 41
CHAPTER FOUR ....................................................................................................... 52
4.1 REVIEW OF LITERATURE ON DECISION THEORY AND INFORMATION
PROCESSING ................................................................................................................ 52
5.
4.1.1
DECISION THEORY .................................................................................... 52
4.1.2
INFORMATION PROCESSING ................................................................... 55
CHAPTER FIVE ......................................................................................................... 58
5.1. CASE STUDY: DESIGN AND SELECTION OF WIRE ROPE MATERIAL FOR
A MANUAL WINCH ..................................................................................................... 58
5.1.1.
5.2.
6
INTRODUCTION ......................................................................................... 58
WIRE ROPE ....................................................................................................... 60
CHAPTER SIX ........................................................................................................... 93
6.1
THE PROCESS OF WIRE ROPE DESIGN FOR A MANUAL WINCH .............. 93
6.1.1
MATERIAL RANKING INDICES................................................................ 93
Availability Index ........................................................................................................ 93
Material Cost Index ..................................................................................................... 93
Manufacturing Index ................................................................................................... 94
Composite index .......................................................................................................... 94
6.2
SUPPORT INFORMATION ................................................................................. 95
6.3
MATERIALS SELECTION PROCESS ................................................................ 95
6.3.1
THE WIRE ROPE MATERIAL SELECTION PROCESS ............................. 97
7
DISCUSSION ............................................................................................................. 99
8
CONCLUSION ......................................................................................................... 101
9
RECOMMENDATIONS........................................................................................... 102
10 REFERENCES & APPENDICES ............................................................................. 103
11 APPENDICES .......................................................................................................... 104
11.1
Tables.............................................................................................................. 104
11.2
Drawings ......................................................................................................... 108
12 THE CODE ............................................................................................................... 110
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OBJECTIVES
1.
To develop a knowledge intensive methodology for screening and ranking engineering
entities, including engineering components, materials and processes, based on the
principles of decision theory.
2.
To automate the selection process so developed as an information processing routine on
a digital computer.
3.
To test, document and evaluate the selection process so developed by means of a case
study (selection of wire rope for a manual winch).
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1
1.1
CHAPTER ONE:
INTRODUCTION
1.1.1 DECISION THEORY
Definition of Decision Theory
Decision theory is the science concerned with identifying the values, uncertainties and other
issues that are relevant in a given decision, its rationality, and the resulting optimal decision.
Most of decision theory is normativeor prescriptive, i.e., it is concerned with identifying the
best decision to take, assuming an ideal decision maker who is fully informed, able to
compute with perfect accuracy, and fully rational. In practice, there are situations in which
“best” is not necessarily the maximal. Optimum may also include values in addition to
maximum, but within a specific or approximate range. The practical application of this
prescriptive approach (how people ought to make decisions) is known as decision analysis,
and it is aimed at finding tools, methodologies and software to help people make better
decisions. The most systematic and comprehensive software tools developed in this way are
called decision support systems.
1.1.2 Kinds of Decision Theory
1.1.2.1 Choice under Uncertainty
The idea of expected value is that, when faced with a number of actions, each of which could
give rise to more than one possible outcome with different probabilities, the rational
procedure is to identify all possible outcomes, determine their values (positive or negative)
and the probabilities that will result from each course of action, and multiply the two to give
an expected value. The action to be chosen should be the one that gives rise to the highest
total expected value.
1.1.2.2 Intertemporal Choice
This area is concerned with the kind of choice where different actions lead to outcomes that
are realised at different points in time. If someone received a windfall of several thousand
dollars, they could spend it on an expensive holiday, giving them immediate pleasure, or they
could invest it in a pension scheme, giving them an income at some time in the future. What
is the optimal thing to do? The answer depends partly on factors such as the expected rates of
interestand inflation, the person’s life expectancy, and their confidence in the pensions
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industry. However even with all those factors taken into account, human behaviour again
deviates greatly from the predictions of prescriptive decision theory, leading to alternative
models in which, for example, objective interest rates are replaced by subjective discount
rates.
1.1.2.3 Competing Decision Makers
Some decisions are difficult because of the need to take into account how other people in the
situation will respond to the decision that is taken. The analysis of such social decisions is
more often treated under the label of game theory, rather than decision theory, though it
involves the same mathematical methods. From the standpoint of game theory most of the
problems treated in decision theory are one-player games (or the one player is viewed as
playing against an impersonal background situation).
1.1.2.4 Complex Decisions
Other areas of decision theory are concerned with decisions that are difficult simply because
of their complexity, or the complexity of the organization that has to make them. In such
cases the issue is not the deviation between real and optimal behaviour, but the difficulty of
determining the optimal behaviour in the first place. The Club of Rome, for example,
developed a model of economic growth and resource usage that helps politicians make reallife decisions in complex situations.
1.1.3 General Criticism
1.1.3.1 Ludic Fallacy
A general criticism of decision theory based on a fixed universe of possibilities is that it
considers the “known unknowns”, not the “unknown unknowns: it focuses on expected
variations, not on unforeseen events, which some argue has outsized impact and must be
considered”. This line of argument, called the ludic fallacy, is that there are inevitable
imperfections in modelling the real world by particular models, and that unquestioning
reliance on models blinds one to their limits.
1.2
HISTORY
The procedure now referred to as expected valuewas known from the 17th century. Blaise
Pascal invoked it in his famous wager, which is contained in his Pensées, published in 1670.
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In 1738, Daniel Bernoullipublished an influential paper entitled Exposition of a New Theory
on the Measurement of Risk, in which he uses the St. Petersburg paradoxto show that
expected value theory must be normativelywrong. He also gives an example in which a
Dutch merchant is trying to decide whether to insure a cargo being sent from Amsterdam to
St Petersburg in winter, when it is known that there is a 5% chance that the ship and cargo
will be lost. In his solution, he defines a utility function and computes expected utilityrather
than expected financial value.
In the 20th century, interest was reignited by Abraham Wald’s1939 paper[2]pointing out that
the two central procedures of sampling-distribution basedstatistical-theory, namely
hypothesis testingand parameter estimation, are special cases of the general decision problem.
Wald’s paper renewed and synthesized many concepts of statistical theory, including loss
functions, risk functions, admissible decision rules, antecedent distributions, Bayesian
procedures, and minimal procedures. The phrase “decision theory” itself was used in 1950
by E. L. Lehmann.
The revival of subjective probabilitytheory, from the work of Frank Ramsey, Bruno de
Finetti, Leonard Savageand others, extended the scope of expected utility theory to situations
where subjective probabilities can be used. At this time, von Neumann's theory of expected
utilityproved that expected utility maximization followed from basic postulates about rational
behaviour.
1.3
A BRIEF DESCRIPTION OF INFORMATION PROCESSING AS APPLIED TO
A MATERIALS SELECTION CASE STUDY
Selecting the proper materials is central to engineering design. It is governed by main factors
which include the design life of the product, availability of the material, service requirement,
the customer preferences and the total life cycle and appropriate data on application.
Therefore, to develop a reliable criterion requires a good understanding of the subject of
study and is a highly challenging decision making process.
An engineer designer requires a high level of fabrication and materials property knowledge in
order to create a successful design. Although various approaches to the materials selection
problem have been developed and used the most rigorous approach is to regard the task at
hand as the development of an entirely new product and thus start from first principals.
Usually, successful selection of standard entities in engineering involves two main steps:
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screening and support information. It is therefore of significance to develop an efficient
method and system in a computer aided concurrent and collaborative environment.
The use of computer aided systems could reduce cost and design rework by providing
engineering design teams with the most current materials property data, knowledge of factors
such as materials options and life cycle costs, and available materials for a design based on
experience derived from previous product development.
A computer aided materials
selection system with learning capabilities would also ensure the proper archiving of material
section decisions for future reference and offer data for comparison between various
decisions.
1.4
STANDARDS AND CODES
A standard is a set of specifications for parts, materials and/or processes intended to achieve
uniformity, efficiency and a specified quality. One of the most important purposes of a
standard is to place a limit on the number of items in the specifications so as to provide a
reasonable inventory of tooling, sizes, shapes and varieties.
A code is a set of specifications for the analysis, design, manufacture and construction of a
system. The purpose of a code is to make sure the system achieves a specified degree of
safety, efficiency, performance and quality. However, it is important to observe that safety
codes do not imply absolute safety.
This project and the case study identify materials to unified numbering system (UNS)
standards. An ideal case of choice of standards should be based on such factors as the
location where the product is applicable and the acceptability of the standard under the
applicable design/construction code. In this case therefore, Kenyan Standards (KS) would
have been preferred.
In order to provide a consistent basis for basic specifications of the materials only UNS
standards for the materials have been used. In some cases where the materials common name
is available the materials common name is given.
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2
2.1
CHAPTER TWO
REVIEW OF LITERATURE ON DESIGN, MATERIAL SELECTION AND
MANUFACTURING
2.1.1 INTRODUCTION
The engineering design process is the formulation of a plan to help an engineer build a
product with a specified performance goal. This process involves a number of steps and parts
of the process may need to be repeated many times before production of a final product can
begin. Therefore design establishes and defines solutions to, and pertinent structures, for
problems not solved before or new solutions to problems which have previously been
resolved in a different.
It involves the decision making process in which the basic sciences, mathematics and
engineering sciences are applied to convert resources optimally to meet a stated objective.
The engineering design process is a multi-step process including the research,
conceptualization, feasibility assessment, establishing design requirements, preliminary
design, detailed design, production planning and tool design and finally production of final
product.
The selection of proper materials is a key step in the design process because is a crucial
decision that links computer calculations and lines on an engineering drawing with a real or
working design. The enormity of this decision process can be appreciated when it’s realized
that there are over forty thousand metallic alloys and probably close to that number of nonmetallic engineering materials, currently in use.
Poor selection of a material, may lead not only to failure of the material but also to
unnecessary cost. Selecting the best material for a part involves more than selecting a
material that has the properties to provide the necessary service performance; it also involves
the processing of the material into a finished part. This is because the properties of the part
may be altered by processing resulting to a change in the service performance of the part.
Much material selection is based on past experiences since we all assume what worked before
obviously is a solution although it might not be the optimum solution. Due to the high
demand to optimize cost and the increase in material shortage a need to select materials on a
rational basis is needed.
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2.1.2 ENGINEERING DESIGN PROCESS
There is no particular step categorization on engineering design process that is universally
accepted. However based on a comparative analysis of the available literature, the design
process can be divided into six broad steps.
Recognition of need
Definition of problem
Iteration
Conceptual design
Preliminary design
Detailed design
Production
Phases in Engineering Design Process (Adapted from: MadaraOgot&Gul Kremer,
Engineering Design: A Practical Guide).
2.1.2.1 RECOGNITION OF NEED
The need for a product typically arises from the following;
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1. The need to design a new product or process that will solve a particular
problem or need where none other exists.
2. The need to redesign: to design a product or process that improves on an
existing one. Improvements include lower cost, higher efficiency, lower
pollution and better ergonomics
3. The need for technology-push product or process: to design a new product or
process and generate need for it.
2.1.2.2 DEFINITION OF THE PROBLEM
Problem definition is probably the most significant step in the engineering design process.
It’s a crucial part in the design process and includes;

Condensed formal problem statement clearly stating objective of the
design process.

Listing of technical and non-technical design constraints.

The specifications of the input and expected output quantities.

The dimensions of the space it must occupy

Breakdown of the problem into smaller manageable sub-problems.

Compilation and ranking of customer needs. What exactly does the
customer expect in final product or process?

Definition of criteria to be used to evaluate the design .e.g. testing of
prototypes developed in preliminary design step.
Poor problem definition will result in the development of a product that does not adequately
meet the need or that may cause failure.
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2.1.2.3 CONCEPTUAL DESIGN
This is the very first phase of design in which drawings or solid models are the dominant
tools and products. The conceptual design phase provides a description of the proposed
system in terms of a set of integrated ideas and concepts and concepts about what it should do
, behave and look like that will be understandable by the users in the manner intended. It
includes industrial designs that define both the aesthetics and functionality of the product and
prototype manufacture.
2.1.2.4 PRELIMINARY DESIGN
Preliminary designs involve the preparation of the drawings which describe all the structural
components and mechanical processes in which they are interrelated. It includes an outline of
the materials and equipment specifications which are then used as a basis for revising earlier
construction cost estimates. Based on the test results parts of the design or the entire design
may need to be redone.
2.1.2.5 DETAILED DESIGN
The detailed design portion of the engineering design process is the task where the engineer
can
completely
describe
a
product
through solid
modelling and drawings.
Some
specifications include:

Operating parameters

Operating and non-operating environmental stimuli

Test requirements

External dimensions

Maintenance and testability provisions

Materials requirements

Reliability requirements

External surface treatment

Design life

Packaging requirements

External marking

tolerances
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The advancement of computer-aided design, or CAD, programs have made the detailed
design phase more efficient. This is because a CAD program can provide optimization, where
it
can
reduce
volume
without
hindering
the
part's
quality.
It
can
also
calculate stress and displacement using the finite element method to determine stresses
throughout the part. It is the engineer's responsibility to determine whether these stresses and
displacements are allowable, so the part is safe virtually all design problems must have been
resolved before the end of the final design stage.
2.1.2.6 PRODUCTION
Prior to production, production process planning is carried out. This involves

Design drawings and specifications interpretation.

Production processes and machines selection.

Stock material selection.

Determination of production sequence of operations.

Determination of processing time.
The implementation involves successful testing of prototypes after which the final solution is
developed and preceded with full production.
2.1.3 MATERIAL SELECTION
Material selection is a critical step in the process of designing any physical object. The
Material Selection Problem in the design of an engineering component involves three
interrelated problems:
(i) Selecting a material,
(ii) Specifying a shape, and
(iii) Choosing a manufacturing process.
In the context of product design, the main goal of material selection is to minimize cost while
meeting product performance goals. Different factors are taken into account in choosing a
material;
1. Material Properties -Involves the expected level of performance from the material.
2. Material Cost- The material must be priced appropriately (not cheap but right)
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3. Availability–The material must be available (better to have multiple sources).
4. Processing –one must consider how to make the part, for example:

Casting

Machining

Welding
5. Environment –in recent years there has been great emphasis on the effects of the
material and/or its production process on the environment and vice versa. This
involves;

The effect that the service environment has on the part

The effect the part has on the environment

The effect that the manufacturing processing has on the environment.
2.1.3.1 MATERIALS SELECTION PROCESS
To realize the above mentioned benefits, engineers have to deal with an extremely complex
problem. There are literally tens of thousands of materials and hundreds of manufacturing
processes. No engineer can expect to know more than a small subset of this ever-growing
body of information. Furthermore, there are demanding and shifting design requirements
such as cost, performance, safety, risk and aesthetics, as well as environmental impact and
recycle-ability. The basic question is how do we go about selecting a material for a given
part? This is a very complicated process but once we realize than we are often restrained by
choices we have already made the problem is made very simple. For example, if different
parts have to interact then material choice becomes limited.
The following procedure is taken from Material Selection in Mechanical Design by Michael
Ashby and involves for basic steps
1. TranslationThis usually involves analysis and stating of the materials performance requirements. It
involves stating
1.1. Function: what the component does, the functional requirements are expressed here.
For instance, the support of a tensile load for a wire rope.
1.2. Objective: these are the essential conditions that must be met. E.g. minimize the cost
and mass.
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1.3. Constraints: these are the properties that are to be maximized or minimized in the
material chosen. Required length and load carrying capacity without failure.
1.4. Free Variables: these are the constraints which can be altered without negatively
affecting the core function of the component such as cross-sectional area and
material used for the wire rope.
2. ScreeningThis is analysis of a large database of materials and their subsequent properties so that
candidate materials that meet the critical material properties can be selected. This is
usually done by dividing the critical properties into 3 groups
a) Non-discriminating parameters are those that must be met if material is to be used
at all. This includes availability of material.
b) Rigid or Go/no-go parameters. These are minimum or maximum property values
which candidate materials must meet. Excess or under values of these fixed
parameters don’t make up for other deficiencies in other properties. Examples
include cost and strength.
c) Soft or Relative or Discriminating parameters. These are minimum or maximum
property values which candidate materials must meet, and where any excess or
under values can make up for other deficiencies in other areas. Includes cost,
density and strength.
Depending on material application, a characteristic that is considered a go/nogo parameter for one application may be considered discriminating or nondiscriminating parameter in another. For example in aerospace applications
cost is a discriminating parameter, whereas in consumer products, cost is a
go/no-go parameter.
It should be noted that there are several methods of screening, some of which include cost per
unit property, Ashby’s selection charts, Dargie’s method or Esawi’s and Ashby’s method.
3. Ranking
If the screening process yields more than one alternative material then this process is
necessary. It involves listing the materials in order of the most appropriate. This is done
using decision tools such as
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3.1. Weighted Property Method
3.2. Pairwise Comparison Charts
3.3. Analytic Hierarchy Charts
3.4. Decision Matrices
4. Supporting InformationThis is usually done after a material is chosen and involves verifying and justifying the
choice made with supporting information.
2.1.4 FACTORS INFLUENCING MATERIAL SELECTION PROCESS
2.1.4.1 MECHANICAL PROPERTIES
The mechanical properties of the metal are those associated with the ability of the material to
resist mechanical forces and load. These mechanical properties of the include;
1. Strength
It is the ability of a material to resist the externally applied forces without breaking or
yielding. The internal resistance offered by a part to an externally applied force is called
stress. Following are parameters of strength:

Elastic Limit: This is the force required to produce permanent deformation.

Yield Point: This refers to the level of the load at which strain continues at a
constant stress.

Yield Strength: The amount of tensile force required to just cause a welldefined permanent deformation in a material.

Ultimate Tensile Strength (UTS): This is the maximum strength of a material
and corresponds to the maximum load stress a structural member can
withstand before fracture.

Compressive Strength: This is the ability of a material to resist a gradually
applied compressive load.
Yield strength and tensile strength are the most significant values in many engineering
applications. Appreciable permanent deformation occurs before the stress reaches the UTS
value. Therefore, to guard against permanent deformation in engineering components,
information on elastic limit of the candidate materials should be used in design. For ductile
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materials, yield point information should be used instead of elastic limit value. For this
project, yield strength and compressive strength of materials have been used as screening
properties in the materials selection process.
2. Stiffness
It is the ability of a material to resist deformation under stress. The modulus of elasticity is
the measure of stiffness.
3. Elasticity
It is the property of a material to regain its original shape after deformation when external
forces are removed. This property is desirable for materials used in tool and machines. It
should be noted that steel is more elastic than rubber.
4. Plasticity
It is a property of a material to retain its original shape after deformation when external forces
are removed. This property is desirable for materials that are forged.
5. Ductility
It is the property of materials to be drawn into wire with the application of a tensile force. A
ductile material must be both strong and plastic. The ductility is usually measured in
percentage elongation or percentage reduction area. The ductile material commonly used in
engineering practice (In order of diminishing ductility) are mild steel, copper, aluminium,
nickel, zinc, tin and lead.
6. Brittleness
This is the property of a material opposite to ductility. It is the property of breaking of a
material with little permanent distortion. Brittle materials when subjected to tensile loads
snap off without giving any sensible elongation.
7. Malleability
It is a special case of ductility which permits materials to be rolled or hammered into thin
sheets. A malleable material should be plastic but it is not essential to be so strong. The
malleable material to be used in engineering practice(in order of diminishing malleability) are
lead, soft steel, wrought iron, copper, aluminium.
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8. Toughness
The property of a material to resist fracture due to high impact loads like hammer blows. The
toughness of a material decreases when a material is heated. It is measured by the amount of
energy that a unit volume of the material has absorbed after being stressed up to a point of
fracture. This property is desirable in parts subjected to shock and impact loads.
9. Machinability.
It is the property of a material which refers to the relative ease with which a material can be
cut. The machinability of a material can be measured in a number of ways such as comparing
tool life for different materials or thrust requires to remove the material at some given rate or
the energy required to remove a unit volume of material... it may be noted that brass can be
more easily machined than steel.
10. Creep
When a part is subjected to a constant stress at a particular temperature for a prolonged period
of time, it will undergo a slow and permanent deformation called creep. This property is
particularly important when designing parts that are in high temperate areas such as internal
combustion components, boilers or furnaces.
11. Fatigue
When a material is subjected to repeated stress it fails at stresses below the yield stress, this
type of failure is known as fatigue failure and is caused by means of a progressive crack
formation and growth which are usually of fine and microscopic size. This property is
important in designing components such as wire ropes, shafts, connecting rods, springs, gears
etc.
12. Hardness
This is a very important property and usually has several meanings. It encompasses many
different properties such as resistance to wear, scratching, deformation and machinability. It
also means the ability of a metal to cut another metal. The hardness is usually expressed in
numbers which are dependent on the method of making the test. The hardness of a metal may
be defined using the following tests:
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
Brinell hardness Test - A test to determine the hardness of metals and alloys by
hydraulically pressing a steel ball into the metal and measuring the resulting
indentation

Rockwell hardness Test - Determines hardness by indicating on a dial the depth of the
impression caused by a loaded indenter in the form of either a diamond cone (Scales
A and C) or a hardened steel ball (Scale B). When the load is removed, the dial gauge
records the depth of impression in terms of Rockwell numbers

Vickers hardness (or diamond pyramid) Test -An indentation hardness test employing
a 136° diamond pyramid indenter (Vickers) and variable loads enabling the use of
one hardness scale for all ranges of hardness from very soft lead to tungsten carbide.

Shore scleroscope- measures hardness in terms of the elasticity of the material. A
diamond-tipped hammer in a graduated glass tube is allowed to fall from a known
height on the specimen to be tested, and the hardness number depends on the height
to which the hammer rebounds; the harder the material, the higher the rebound.
2.1.5 MECHANICAL FAILURE MODES
Failure modes are the physical processes that take place or combine their effects to produce
failure. The following are the failure modes most commonly observes in machine and
machine parts.
1. Force and\or temperature induced deformation- This occurs whenever elastic or
recoverable deformation in a machine component brought about by the imposed
operational loads or temperature becomes great enough to interfere with the ability of
the machine to satisfactorily perform it intended function.
2. Yielding- This occurs when the imposed loads and motions on a component are
enough to cause plastic deformation which results in the unsatisfactory performance
of the member.
3. Brinelling – This results when the static load between 2 curved surfaces is enough to
cause plastic deformation in one or both of the members
4. Ductile rupture – This occurs when the plastic deformation in a component that
exhibit ductile behaviour is carried to an extreme that the component breaks into 2
pieces.
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5. Brittle Fracture- This occurs when the elastic deformation in a component that exhibit
brittle behaviour is carried to an extreme that the component breaks into two or more
pieces.
6. Fatigue - Fatigue is the general term that is given to progressive and localized
structural damage that occurs when a material is subjected to cyclic loading. It occurs
when a material is subjected to repeated loading and unloading. If the loads are above
a certain threshold, microscopic cracks will begin to form at the surface. Eventually a
crack will reach a critical size, and the structure will suddenly fracture. Fatigue can be
divided into:
a. High – cycle fatigue
b. Low-cycle fatigue
c. Thermal fatigue
d. Surface Fatigue
e. Impact Fatigue
f. Corrosion fatigue
g. Fretting fatigue
Corrosion - Corrosion is broad term which generally refers to a machine component being
rendered incapable of performing due to the disintegration of its engineering material into its
constituent atoms due to chemical reactions with its surroundings.
It involves
electrochemical oxidation of metals in reaction with an oxidant such as oxygen. A wellknown example of electrochemical corrosion is formation of an oxide iron due to oxidation of
the iron atoms in solid solution. Effects of corrosion are magnified by stress concentration
and cyclic loading. Corrosion can be divided into:
a. Direct Chemical attack
b. Galvanic corrosion
c. Pitting Corrosion
d. Inter-granular corrosion
e. Selective leaching
f. Erosion Corrosion
g. Cavitation corrosion
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h. Hydrogen damage
i. Biological corrosion
j. Stress corrosion
7. Wear– this is the undesired cumulative change in dimension brought about by the
gradual removal of discrete particles from contacting surfaces in motion, usually
sliding, predominantly as a result of mechanical action. Wear can be divided into
a. Adhesive wear
b. Abrasive wear
c. Corrosive wear
d. Surface fatigue wear
e. Deformation wear
f. Impact wear
g. Fretting wear
8. Impact– this results when a component in a machine is subjected to non-static loads
that produce stresses or deformation in the member of such magnitude of such
magnitude that the component cannot perform as intended. The failure is brought
about by the interaction of stress or strain waves generated by dynamic or suddenly
applied loads which may induce stresses or strains that are many times greater than
would have induced by static loads. This mode of failure can be dived into:
a. Impact fracture
b. Impact deformation
c. Impact fretting
d. Impact fatigue
e. Impact wear
9. Fretting – This may occur at the interface between any two solid bodies whenever
they are pressed together by a normal force and subjected to a small amplitude cyclic
relative motion with respect to each other. Fretting usually occurs in joints that are not
intended to move but, due to vibrations, experience minute cyclic relative motions ant
the debris from fretting is trapped between the surfaces because of the motion
involved.
a. Fretting fatigue
b. Fretting wear
c. Fretting corrosion
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10. Creep- Creep is a slow or progressive deformation of a material with time under
constant stress and/or temperature until the accumulated dimensional changes
interfere with the performance of the component. It is triggered via thermal activation
and is more severe in materials that are subjected to heat for long periods near the
melting point.
11. Thermal/Stress relaxation– this occurs when the dimensional changes due to the creep
process result in the relaxation of a pre-strained or preloaded member until it is no
longer able to perform its intended function
12. Stress Rapture – this is intimately related to the creep process except that the
combination of stress time and temperature is such that rupture into two parts of the
component is assured.
13. Thermal shock– this occurs when the thermal gradients in a machine part is so
pronounced that differential thermal strains exceeds the ability of the material to
sustain them without yielding or fracture.
14. Galling and seizure – this occurs when two sliding surface in contact are subjected to
such a combination of loads, sliding velocities, temperatures,, environments and
lubricants that massive surface destruction by welding and tearing, ploughing,
gouging, plastic deformation and metal transfer between the two surfaces. Seizure is
an extension of galling to such an extent that the two surfaces are welded together and
relative motion is impaired.
15. Sapling – this occurs whenever a particle is spontaneously dislodged from the surface
of a machine part so as to prevent proper function of the component.
16. Radiation damage – this occurs when the changes in material properties induced by
exposure to nuclear radiation are of such a type and magnitude as to render the
component unable to perform it function properly, usually as a result of triggering
some other type of failure e.g. loss of ductility in elastomers
17. Buckling–this occurs when, due to a critical combination of magnitude and/or pointof-load application, together with the geometric configuration of a component, the
deflection of the component greatly increases with only a slight increase in load. This
non-linear deformation results in buckling failure if the buckled component is no
longer able to function properly
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18. Creep buckling – this occurs when, after a period of time, the creep process results in
an unstable combination of the loading and geometry of a machine part so that the
critical buckling limit is surpassed and failure ensues.
19. Stress corrosion – this occurs when the applied stresses on a machine part in a
corrosive environment generate a field of localized surface cracks, usually along grain
boundaries, that render that part incapable of performing its function, often because of
triggering some other mode of failure. This is a very important form of failure
because so many metals are susceptible to it.
20. Corrosion wear – this is failure of a combination of failure modes in which corrosion
and wear combine their deleterious effects to incapacitate the machine component.
The corrosion process often produces a hard abrasive material that accelerates the
wear, while the wear process constantly removes the protective corrosion layer from
the surface, exposing more metal to the corrosive substance and thus accelerating the
corrosion process.
21. Corrosion fatigue – this is a combination of failure modes in which corrosion and
fatigue combine their effects to cause component failure. The corrosion process often
forms pits and surface discontinues that act as stress raisers that in turn accelerate
fatigue failure. Further, cracks in the usually brittle corrosion layer also act as fatigue
crack nuclei that propagate into the base of the materials. On the other hand, the
cyclic loads and strains cause cracking and flacking of the corrosion layer.
22. Combined creep and fatigue – this is a combination of the 2 failure modes in which
all the condition for both creep and fatigue failure exist simultaneously, each process
influencing the other to produce accelerated failure.
Identification of the most probable governing failure modes by a designer is an essential step
that should be undertaken early in the design of any machine part. The design should provide
a safe, reliable, cost effective operation throughout the design lifetime.
2.1.6 PHYSICAL PROPERTIES
A. Density
Density is commonly defined as mass per unit volume. It is the weight of a material per unit
volume and is measured by weighing it in air and in a fluid of known density. Different
engineering applications demand different density requirements from materials. Low density
materials may be preferred in some applications like in aircraft components (fuel economy).
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On the contrary, weight is found to be advantageous in some cases such as while making
foundations and flywheels.
B. Thermal Properties
1. Thermal conductivity
It is the measure of the rate at which heat can be conducted through a material.
Conduction is the heat transfer process where thermal energy is transferred within a
material purely by thermal motion, without the transfer of mass. Thermal conductivity
is measured with the coefficient of thermal conductivity k. the higher the coefficient,
the better the thermal conductivity.
2. Specific heat
It is the amount of thermal energy required to increase a unit mass of a temperature by
1 degree.
3. Coefficient of thermal expansion
It gives a measure of an object’s change in length per degree change in temperature.
The higher a materials coefficient of thermal expansion, the more it expands and
contracts from temperature changes.
C. Electrical Properties
1. Resistivity
Electricity flows through solid materials and liquids via electrons and ions,
respectively. Resistivity measures a materials ability to resist electricity; the higher its
value the higher the resistance of the material. However resistivity changes with
temperature. For example, as the temperature of a metal is raised, its resistivity goes
up.
2. Dielectric strength
Materials can be categorized in terms in terms of their electrical properties as
conductors, semi-conductors, or insulators. For an insulator the dielectric strength is
the voltage required to break down the insulation through a unit thickness of the
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material. The higher the dielectric strength the grater the voltage the material can
insulate against.
2.1.7 MANUFACTURING PROCESS
1. Machining
Machining is the creation of a final desired shape using cutting tools to remove excess
material from a work piece. Examples include milling, turning and drilling. It plays a key role
in manufacturing process as it;

Is applicable to a wide variety of materials; nearly all solid metals and most plastics.

Allows the generation of regular geometries for example flat planes, holes and arcs
whose combination can produce a wide variety of shapes.

Can achieve very tight tolerances as compared to other processes ≥ 0.001

Can yield very smooth surfaces as compared to other processes ≥0.16µin
Therefore machining is used to obtain the final geometry dimension and finish of a part after
another process has been used to get the part to the rough shape.
2. Plastic injection moulding
Plastic injection is the most common process for manufacturing plastic products. It involves:



Heating a polymer to a molten state.
Forcing the molten polymer to flow into a mould.
Cooling and removing the moulded part.
This process is suitable for large scale production. In such production scale, the expenditure
on tooling cost is high, and therefore it’s important that the designer consults the
manufacturer at an early stage in design.
3. Casting
Metal casting is the process by which a metal or a metal alloy is poured into a mould and
hardened in the shape of the mould cavity. It allows the creation parts both with internal and
external shapes. It is well suited for mass production. The casting process involves:



Melting the metal.
Pouring the molten metal into the mould.
Allowing the metal to cool and solidify.
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
Removing the finished part from the mould.
Casting is applicable to any metal that can be heated to a liquid state. Some casting processes
can produce the finished product without the need for further machining process.
4. Case hardening
The purpose of case hardening is to produce a hard outer surface on a specimen of low
carbon steel while at the same time retaining the ductility and toughness in the core.
This is done by increasing the carbon content at the surface by using solid, liquid, or gaseous
carburizing materials. The process consists of introducing the part to be carburized into the
carburizing material for a stated time, and temperature depending upon the depth of case
desired and the composition of the part. The part may then be quenched directly from the
carburization temperature and tempered, or in some cases it must undergo a double heat
treatment in order to ensure that both the core and the case are in proper condition. Some of
the more useful case-hardening processes are pack carburizing, gas carburizing, nitriding,
cyaniding, induction hardening, and flame hardening.
5. Rolling
Rolling uses two opposing rolls to draw material into the gap between them, thereby reducing
the material’s thickness. The geometry of the product depends on the contour of the roll gap.
Roll materials are cast iron cast steel and forged steel because of high strength and wear
resistance. In rolling the crystals get elongated in the rolling direction. In cold rolling, the
crystal more or less retains the elongated shape but in hot rolling they start reforming after
coming out from the deformation zone.
6. Powder metallurgy
The powder metallurgy process is a quantity–production process that uses powders from a
single metal, several metals, or a mixture of metals and non-metals. Essentially it consists of
mechanically mixing the powders, compacting them in dies at high pressures and heating the
compacted part at a temperature less than the melting point of the major ingredient. Waste
material and machining operations are reduced significantly. However, the cost of materials
and dies are high. Parts commonly made by this process are: Oil impregnated bearings,
incandescent lamp filaments, cemented carbide tips for tools and permanent magnet.
7. Forging
Forging uses compressive forces to generate distinct shapes using die hammers and hydraulic
presses. Die hammers deform the material with a series of high velocity impacts. Hydraulic
presses deform the material through controlled high pressure motion. All metals are forgeable
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to different degrees. Forgability is a subjective measure of the extent to which the material
can be deformed. It depends on the metal’s composition, crystalline structure and mechanical
properties.
8. Extrusion
Extrusion is a process that reduces the cross section of a block of metal by forcing it through
a die orifice under high pressure. As a result extruded products have uniform cross section
along their entire length. This process is generally used to produce cylindrical bars or hollow
tubes. Extrusion is primarily a hot working process, achieving considerable shape changes in
a single operation and making it possible to form complex sections that cannot be produced
in other ways. It offers economic advantages because dies are relatively inexpensive and
interchangeable allowing one machine to be used for the production of a wide variety of
sections.
9. Drawing
Large quantities of wires, rods, tubes and other sections are produced by drawing process
which is basically a cold working process. In this process the material is pulled through a die
in order to reduce it to the desired shape and size. In a typical wire drawing operation, one
end of the wire is reduced and passed through the opening of the die, gripped and pulled to
reduce its diameter. By successive drawing operation through dies of reducing diameter the
wire can be reduced to a very small diameter. Annealing before each drawing operation
permits large area reduction.
2.1.8 COMMERCIAL PROPERTIES (COST AND AVAILABILITY)
These properties involve aspects of both direct cost of materials and availability of materials.
This is because availability of a material greatly determines its cost. A material is selected
bearing in mind the cost of manufacture using available methods. Other costs include:

The cost of labour required to produce the finished product from that material.

Cost of indirect materials (processing chemicals and cleaning materials).

Cost of services incurred (electric power, gas, air, water, coal, and fuel).

Tool replacement cost.

Depreciation of plant and machinery.
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2.1.9 REGULATORY PROPERTIES
A. Code Acceptance
Professional Engineering organisations provide performance oriented codes, standards and
evaluation procedures by which a product can be tested and evaluated for compliance. This
helps provide a uniform and widely recognised basis for acceptance of new products. After
the new product has been tested to indicate conformance to the code, a technical report is
issued describing the new system, the information and the tests submitted, and the
recommended usage.
B. Reparability
This is the ability of the damaged or failed equipment, machine or system to be restored to
acceptable operating condition within a specified time. This property should be taken into
account to avoid losses that would be suffered if replacement was to be done for whole
component or equipment. The spare parts should be available and affordable.
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3
3.1
CHAPTER THREE
LITERATURE REVIEW ON ENGINEERING MATERIALS, THEIR
CATEGORIES AND PROPERTIES.
3.1.1 INTRODUCTION
Materials science in engineering plays a vital role in this modern age of science and
technology. Various kinds of materials are used in industry, housing, agriculture,
transportation, etc. to meet the plant and individual requirements. The rapid developments in
the field of theory of solids have opened vast opportunities for better understanding and
utilization of various materials.
The selection of a specific material for a particular use is a very complex process. However,
one can simplify the choice if the details about
(i) Operating Parameters,
(Ii) Manufacturing Processes
(Iii) Functional Requirements
(Iv) Cost considerations
Factors affecting the selection of materials are summarized in Table 1.1.
Manufacturing
Functional
Cost
Operating
Process
Requirements
Considerations
Parameters
Plasticity
Strength
Raw
Pressure
Material
Malleability
Hardness
Processing
Temperature
Ductility
Rigidity
Storage
Flow
Machinability
Toughness
Manpower
Material
Type
Castability
Thermal
Special
Conductivity
Treatment
Weldability
Fatigue
Inspection
Environment
Heat
Electrical
Packaging
Fire
Treatment
Tooling
Creep
Corrosion
Resistance
Inventory
Weathering
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Surface
Aesthetic look
Taxes
Finish
Biological
effects
There are thousands and thousands of materials available and it is very difficult for an
Engineer to possess a detailed knowledge of all the materials. However, a good grasp of the
fundamental principles which control the properties of various materials help one to make the
optimum selection of material. In this respect, materials science and engineering draw heavily
from the engineering branches, e.g. metallurgy, ceramics and polymer science.
3.1.2 ENGINEERING REQUIREMENTS
While selecting materials for engineering purposes, mechanical properties such as impact
strength, tensile strength, hardness indicate the suitability for selection. One can dictate the
method of production of the component, service life, cost etc. Also, chemical properties of
materials, e.g. structure, bonding energy, resistance to environmental degradation also effect
the selection of materials for engineering purposes.
In recent years polymeric materials or plastics have gained considerable popularity as
engineering materials. Though inferior to most metallic materials in strength and temperature
resistance, these are being used not only in corrosive environment but also in the places
where minimum wear is required, e.g. small gear wheels, originally produced from hardened
steels, and are now being manufactured from nylon or Teflon. These materials perform
satisfactorily, are quiet and do not require lubrication.
Thus, before selecting a material or designing a component, it is essential for one to
understand the requirements of the process thoroughly, operating limitations like hazardous
or non-hazardous conditions, continuous or non-continuous operation, availability of raw
materials as well as spares, availability of alternate materials and life span of the
instrument/equipment, cost etc. Different materials possess different properties to meet the
various requirements for engineering purposes. The properties of materials which dictate the
selection are as follows:
(a) Mechanical Properties: The important mechanical properties affecting the selection of a
material are:
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(i) Tensile Strength: This enables the material to resist the application of a tensile force. To
withstand the tensile force, the internal structure of the material provides the internal
resistance.
(ii) Hardness: It is the degree of resistance to indentation or scratching, abrasion and wear.
Alloying techniques and heat treatment help to achieve the same.
(iii) Ductility: This is the property of a metal by virtue of which it can be drawn into wires or
elongated before rupture takes place. It depends upon the grain size of the metal crystals.
(iv) Impact Strength: It is the energy required per unit cross-sectional area to fracture a
specimen, i.e., it is a measure of the response of a material to shock loading.
(v) Wear Resistance: The ability of a material to resist friction wear under particular
conditions, i.e. to maintain its physical dimensions when in sliding or rolling contact with a
second member.
(vi) Corrosion Resistance: Those metals and alloys which can withstand the corrosive action
of a medium i.e. corrosion processes precede in them at a relatively low rate are termed
corrosion-resistant.
(vii) Density: This is an important factor of a material where weight and thus the mass is
critical, i.e. aircraft components.
(b) Thermal Properties The characteristics of a material, which are functions of the
temperature, aretermed its thermal properties. One can predict the performance of machine
components during normal operation, if he has the knowledge of thermal properties. Specific
heat, latent heat, thermal conductivity, thermal expansion, thermal stresses, thermal fatigue,
etc. are few important thermal properties of materials.
These properties play a vital role in selection of material for engineering applications, e.g.
when materials are considered for high temperature service. Now, we briefly discuss few of
these properties:
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(i) Specific Heat (c): It is the heat capacity of a unit mass of a homogeneous substance. One
can also define it as the quantity of heat required to raise the temperature of a unit mass of the
substance through 1°C.
(ii) Thermal Conductivity (K): This represents the amount of heat conducted per unit time
through a unit area perpendicular to the direction of heat conduction when the temperature
gradient across the heat conducting element is one unit. The higher the value of thermal
conductivity, the greater is the rate at which heat will be transferred through a piece of given
size. Copper and aluminium are good conductors of heat and therefore extensively used
whenever transfer of heat is desired. Bakelite is a poor conductor of heat and hence used as
heat insulator.
(iii) Thermal Expansion: All solids expand on heating and contract on cooling. Thermal
expansion may take place as linear, circumferential or cubical. A solid which expands equally
in three mutually orthogonal directions is termed as thermally isotropic. The increase in any
linear dimension of a solid, e.g. length, width, height on heating is termed as linear
expansion. The coefficient of linear expansion is the increase in length per unit length per
degree rise in temperature.
(iv) Thermal Resistance (RT): It is the resistance offered by the conductor when heat flow
due to temperature difference between two points of a conductor. It is given by
(v) Thermal Diffusivity (h): A material having high heat requirement per unit volume
possesses a low thermal diffusivity because more heat must be added to or removed from the
material for effecting a temperature change.
(vi) Thermal Fatigue: This is the mechanical effect of repeated thermal stresses caused by
repeated heating and cooling. The thermal stresses can be very large, involving considerable
plastic flow. We can see that fatigue failures can occur after relatively few cycles.
(c) Electrical Properties Conductivity, resistivity, dielectric strength are few important
electrical properties of a material. A material which offers little resistance to the passage of
an electric current is said tube a good conductor of electricity.
Usually resistivity of a material is quoted in the literature. Unit of resistivity is Ohm-metre.
On the basis of electrical resistivity materials are divided as: (i) Conductors (ii)
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Semiconductors and(iii) Insulators. In general metals are good conductors. Insulators have
very high resistivity. Ceramic insulators are most common examples and are used on
automobile spark plugs, Bakelite handles for electric iron, and plastic coverings on cables in
domestic wiring.
When a large number of metals and alloys are sufficiently cooled below transition
temperature, Tc, enter the state of superconductivity in which the dc resistivity goes to zero.
The estimates of the resistivity in the super-conducting phase place it at less than 4 X 10–
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ohm-m, which is essentially zero for all practical purposes.
(d) Magnetic Properties Materials in which a state of magnetism can be induced are termed
magnetic materials. There are five classes into which magnetic materials may be grouped: (i)
diamagnetic (ii) paramagnetic(iii) ferromagnetic (iv) ant ferromagnetic and (v) ferromagnetic.
Iron, Cobalt, Nickel and some of their alloys and compounds possess spontaneous
magnetization. Magnetic oxides like ferrites and garnets could be used at high frequencies.
Because of their excellent magnetic properties along with their high electrical resistivity these
materials today find use in a variety of applications like magnetic recording tapes,inductors
and transformers, memory elements, microwave devices, bubble domain devices, recording
hard core’s, etc. Hysteresis, permeability and coercive forces are some of the magnetic
properties of magnetic substances which are to be considered for the manufacture of
transformers and other electronic components.
(e) Chemical Properties These properties includes atomic weight, molecular weight, atomic
number,valency, chemical composition, acidity, alkalinity, etc. These properties govern the
selection of materials particularly in Chemical plant.
(f) Optical Properties The optical properties of materials, e.g. refractive index, reflectivity
and absorption coefficient etc. affect the light reflection and transmission.
(g) Structure of Materials The properties of engineering materials mainly depends on the
internal arrangement of the atoms on molecules. We must note that in the selection of
materials, the awareness regarding differences and similarities between materials is extremely
important. Metals of a single type atom are named pure metals. Metals in actual commercial
use are almost exclusively alloys, and not pure metals, since it is possible for the designer to
realize an infinite variety of physical properties in the product by varying the metallic
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composition of the alloy. Alloys are prepared from mixed types of atoms. Alloys are
classified as binary alloys, composed of two components, as ternary alloys, composed of
three components or as multi component alloys. Most commercial alloys are
multicomponent.
The composition of an alloy is described by giving the percentage (either by weight or by
atoms)of each element in it. The basic atomic arrangement or pattern is not apparent in the
final component, e.g. a wire rope, but the properties of the individual crystals within the
metallic component, which are controlled by the atomic arrangement, are mainly responsible
for their application in industry. One can determine the strength of a piece of metal by its
ability to withstand external loading. The structure of metal or alloy responds internally to the
applied load by trying to counteract the magnitude of the applied load and thus tries to keep
the constituent atoms in their ordered positions if however the loads higher than the force
which holds the atoms in place, the metallic bond becomes ineffective and atoms in the metal
are then forced into new displaced positions. The movement of atoms from their original
positions in the metal is termed as slip. The ease where atoms move or slip in a metal is an
indication of hardness. We must note that the relative movement of atoms or slip within a
material has a direct bearing on the mechanical properties of the material.
3.1.3 CLASSIFICATION OF MATERIALS
The factors which form the basis of various systems of classifications of materials in material
science and engineering are:
(i) the chemical composition of the material,
(ii) the mode of the occurrence of the material in the nature,
(iii) the refining and the manufacturing process to which the material is subjected prior it
acquires the required properties,
(iv) the atomic and crystalline structure of material and
(v) the industrial and technical use of the material.
Common engineering materials that fall within the scope of material science and engineering
are normally placed in two broad categories, namely Metallic and non-metallic compounds,
but they may be further classified into one of the following six groups:
(i) Metals (ferrous and non-ferrous) and alloys
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(ii) Ceramics
(iii) Polymers
(iv) Composites
(v) Semi-conductors
(vi) Biomaterials
(vii) Advanced Materials
A Table showing the different categories materials fall into is shown below.
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ENGINEERING
Non-Metals
Metal & Alloys
Composite
Ferrous
Steels
Ceramic
Polymer
Semiconductor
BioMaterial
Non
Cast
Titaniu
Coppe
Nicke
Magnesiu
Aluminiu
Carbon
Alloy
steels
High
HSLA
High
alloy
Medium
Austenitic
Low
Ferriti
Martensiti
Duple
x
Note: HSLA –High Strength Low Alloy
Fig. 3.2: Categories of engineering materials
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3.1.4 METALLIC MATERIALS
These consist of metals and metal alloys. Metals are element substances which readily give
up electrons to form metallic bonds and conduct electricity.
When two or more pure metals are melted together to form a new metal whose properties are
quite different from those of original metals, it is called an alloy.
Metallic materials possess specific properties like plasticity and strength. Few favourable
characteristics of metallic materials are high lustre, hardness, resistance to corrosion, good
thermal and electrical conductivity, malleability, stiffness, the property of magnetism, etc.
Metals may be magnetic, non-magnetic in nature. These properties of metallic materials are
due to: (i) the atoms of which these metallic materials are composed and (ii) the way in which
these atoms are arranged in the space lattice.
In this category we have ferrous and non-ferrous metals. They have vast application due to
their good electrical and thermal conductivity.
3.1.4.1 FERROUS ALLOYS
Ferrous alloys contain iron as the prime constituent. Their widespread use is accounted for by
three factors:

Iron-containing compounds exist in abundant quantities within the earth’s crust

Metallic iron and steel alloys may be produced using relatively economical extraction,
refining, alloying, and fabrication techniques.

Ferrous alloys are extremely versatile, in that they may be tailored to have a wide
range of mechanical and physical properties. The principal disadvantage of many
ferrous alloys is their susceptibility to corrosion.
3.1.4.1.1 STEELS
Steels are iron–carbon alloys that may contain appreciable concentrations of other alloying
elements. The mechanical properties are sensitive to the content of carbon, which is normally
less than 1.0 wt%. Steels are classified according to carbon concentration, namely, into low,
medium, and high carbon types.
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A. Low-Carbon Steels
Have carbon content of less than 0.25 wt%. Microstructures consist of ferrite and pearlite
constituents. As a consequence, these alloys are relatively soft and weak, but have
outstanding ductility and toughness; in addition, they are machinable, weldable. A sub group
of low-carbon alloys are the high-strength, low-alloy (HSLA) steels. They contain other
alloying elements such as copper, vanadium, nickel, and molybdenum in combined
concentrations as high as 10 wt%, and possess higher strengths.
B. Medium-Carbon Steels
Have carbon concentrations between about 0.25 and 0.60wt%. These alloys may be heat
treated by austenitizing, quenching, and then tempering to improve their mechanical
properties. They are most often utilized in the tempered condition, having microstructures of
tempered martensite. The plain medium-carbon steels have low harden abilities and can be
successfully heat treated only in very thin sections and with very rapid quenching rates.
C. High-Carbon Steels
Have carbon contents between 0.60 and 1.4 wt%. They are the hardest, strongest, and yet
least ductile of the carbon steels. Used in a hardened and tempered condition and, as such, are
especially wear resistant and capable of holding a sharp cutting edge. The tool and die steels
are high-carbon alloys, usually containing chromium, vanadium, tungsten, and molybdenum.
These alloying elements combine with carbon to form very hard and wear-resistant carbide
compounds.
3.1.4.1.2 STAINLESS STEELS
The stainless steels are highly resistant to corrosion. Their predominant alloying element is
Chromium with a concentration of at least 11 wt%. Corrosion resistance may also be
enhanced by nickel and molybdenum additions. They are divided into three classes:

Ferrite steels: contain 12-27% chromium.

Martens tic steels: contain 12% chromium and no nickel.

Austensitic steels: contain 18% chromium and 8% nickel
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3.1.4.1.3 CAST IRONS
Generically, cast irons are a class of ferrous alloys with carbon content above 2.14 wt %.
However, most cast irons contain between 3.0 and 4.5 wt% C and, other alloying elements.
They are easily melted and amenable to casting. Cast irons are grouped into:
A. Gray cast Iron
The carbon content varies between 2.5 - 4.0 wt percent, with Silicon content varying between
1.0 - 3.0 wt%. The graphite exists in the form of flakes (similar to corn flakes), which are
normally surrounded by ferrite or pearlite matrix. It’s weak and brittle in tension as a
consequence of its microstructure; the tips of the graphite flakes are sharp and pointed, and
may serve as points of stress concentration when an external tensile stress is applied. Strength
and ductility are much higher under compressive loads. They are very effective in damping
vibration energy.
B. Ductile (or Nodular) Iron
It is formed by adding a small amount of magnesium and/or cerium to the Gray iron before
casting. Graphite forms as nodules or sphere-like particles instead of flakes. The matrix phase
surrounding these particles is either pearlite or ferrite, depending on heat treatment. It is
normally pearlite for a cast piece. However, heat treatments for several hours at about 700 0C
will yield a ferrite matrix .Castings are stronger and much more ductile than Gray cast iron.
Ductile cast iron has mechanical characteristics approaching those of steel.
C. White cast Iron and Malleable cast Iron
White cast iron contains low-silicon (less than 1.0 wt% Si) and undergoes rapid cooling rates.
Carbon exists as cementite instead of graphite. It is extremely hard but also very brittle, to the
point of being virtually unmachinable. White iron is used as an intermediary in the
production of malleable iron. Heating white iron at temperatures between 800- 9000C for a
prolonged time period and in a neutral atmosphere (to prevent oxidation) causes a
decomposition of the cementite, forming graphite, which exists in the form of clusters or
rosettes surrounded by a ferrite or pearlite matrix, depending on cooling rate. The
microstructure of malleable iron is similar to that for nodular iron hence it’s relatively high
strength and appreciable ductility or malleability.
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3.1.4.2 NON-FERROUS ALLOYS
Steel and other ferrous alloys are consumed in exceedingly large quantities because they have
such a wide range of mechanical properties, may be fabricated with relative ease, and are
economical to produce. However, they have some distinct limitations, chiefly:

Relatively high density,

Comparatively low electrical conductivity, and

An inherent susceptibility to corrosion in some common environments.
Thus, for many applications it is advantageous or even necessary to utilize other alloys
having more suitable property combinations. Alloy systems are classified either according to
the base metal or according to some specific characteristic that a group of alloys share.
3.1.4.3 COPPER AND ITS ALLOYS
Copper and copper-based alloys, possessing a desirable combination of physical properties,
have been utilized in quite a variety of applications since antiquity.
A. Copper
Unalloyed copper has excellent thermal and electrical conductivity. It is soft, ductile, and has
an almost unlimited capacity to be cold worked. It is highly resistant to corrosion in diverse
environments including the ambient atmosphere, seawater, and some industrial chemicals.
The mechanical and corrosion-resistance properties of copper may be improved by alloying.
Most copper alloys cannot be hardened or strengthened by heat-treating procedures;
consequently, cold working and/or solid-solution alloying must be utilized to improve these
mechanical properties.
B. Copper alloys
a) Brasses
Zinc is the predominant alloying element. αbrasses are relatively soft, ductile, and easily cold
worked. Brass alloys having higher zinc content contain both αand β phases at room
temperature. The β phase has an ordered body centred cubic (BCC) crystal structure and is
harder and stronger than α phase; consequently, α+β alloys are generally hot worked. Some
of the common brasses are yellow, naval, and cartridge brass, muntz metal, and gilding metal.
b) Bronze
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The bronzes are alloys of copper and several other elements, including tin, aluminium,
silicon, and nickel. These alloys are somewhat stronger than the brasses, yet they still have a
high degree of corrosion resistance. Generally they are utilized when, in addition to corrosion
resistance, good tensile properties are required.
c) Beryllium coppers
They possess a remarkable combination of properties: tensile strengths as high as 1400 MPa,
excellent electrical and corrosion properties, and wear resistance when properly lubricated;
they may be cast, hot worked, or cold worked. High strengths are attained by precipitationhardening heat treatments. These alloys are costly because of the beryllium additions, which
range between 1.0 and 2.5 wt%. Applications include jet aircraft landing gear bearings and
bushings, springs, and surgical and dental instruments.
3.1.4.4 ALUMINIUM AND ITS ALLOYS
Aluminium and its alloys are characterized by a relatively low density (2700Kg/m3), high
ductility, high electrical- thermal conductivities, and a resistance to corrosion.
Since
aluminium has a face centred cubic (FCC) crystal structure, its ductility is retained even at
very low temperatures. The chief limitation of aluminium is its low melting temperature,
which restricts the maximum temperature at which it can be used. Principal alloying elements
include copper, magnesium, silicon, manganese, and zinc.
Aluminium alloys are classified as either cast or wrought. Some of the more common
applications of aluminium alloys include aircraft structural parts, beverage cans, bus bodies,
and automotive parts (engine blocks, pistons, and manifolds).Recent attention has been given
to alloys of aluminium and other low-density metals (e.g. Mg and Ti) as engineering
materials for transportation, to effect reductions in fuel consumption. An important
characteristic of these materials is specific strength, which is quantified by the tensile
strength–specific gravity ratio.
A generation of new aluminium-lithium alloys has been developed recently for use by the
aircraft and aerospace industries. These materials have relatively low densities (between
2500–2600 Kg/m3), high specific moduli (elastic modulus specific gravity ratios), and
excellent fatigue and low-temperature toughness properties.
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3.1.4.5 MAGNESIUM AND ITS ALLOYS
The most outstanding characteristic of magnesium is its density (1700 Kg/m3); hence its
alloys are used where light weight is an important consideration (e.g. in aircraft
components).It is relatively soft, and has a low elastic modulus. At room temperature
magnesium and its alloys are difficult to deform. Consequently, most fabrication is by casting
or hot working. It has a moderately low melting temperature. Chemically, magnesium alloys
are relatively unstable and especially susceptible to corrosion in marine environments. On the
other hand, corrosion or oxidation resistance is reasonably good in the normal atmosphere
(due to impurities). Fine magnesium powder ignites easily when heated in air; consequently,
care should be exercised when handling it in this state.
These alloys are also classified as either cast or wrought, and some of them are heat treatable.
Aluminium, zinc, manganese, and some of the rare earths are the major alloying elements.
These alloys are used in aircraft and missile applications.
3.1.4.6 TITANIUM AND ITS ALLOYS
Titanium and its alloys are relatively new engineering materials that possess an extraordinary
combination of properties. The pure metal has a relatively low density (4500 Kg/m3), a high
melting point [16680C], and an elastic modulus of 107 GPa. Titanium alloys are extremely
strong, with room temperature tensile strengths as high as 1400 MPa. Furthermore, the alloys
are highly ductile, easily forged and machined.
The major limitation of titanium is its chemical reactivity with other materials at elevated
temperatures. This property has necessitated the development of nonconventional refining,
melting, and casting techniques; consequently, titanium alloys are quite expensive. In spite of
this high temperature reactivity, the corrosion resistance of titanium alloys at normal
temperatures is unusually high; they are virtually immune to air, marine, and a variety of
industrial environments
They are commonly utilized in airplane structures, space vehicles, surgical implants, and in
the petroleum and chemical industries.
3.1.4.7 THE SUPER ALLOYS
The super-alloys have superlative combinations of properties. Most are used in aircraft
turbine components, which must withstand exposure to severely oxidizing environments and
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high temperatures for reasonable time periods. Mechanical integrity under these conditions is
critical; in this regard, density is an important consideration because centrifugal stresses are
diminished in rotating members when the density is reduced. These materials are classified
according to the predominant metal in the alloy, which may be cobalt, nickel, or iron. Other
alloying elements include the refractory metals (Nb, Mo, W, and Ta), chromium, and
titanium. In addition to turbine applications, these alloys are utilized in nuclear reactors and
petrochemical equipment.
3.1.4.8 MISCELLANEOUS ALLOYS NON-FERROUS
The discussion above covers the vast majority of non-ferrous alloys; however, a number of
others are found in a variety of engineering applications. These include:
a) Nickel and its alloys are highly resistant to corrosion in many environments, especially
those that are basic (alkaline). Nickel is often coated or plated on some metals that are
susceptible to corrosion as a protective measure. Monel, a nickel based alloy containing
approximately 65 wt% Ni and 28 wt% Cu (the balance iron), has very high strength and is
extremely corrosion resistant; it is used in pumps, valves, and other components that are in
contact with some acid and petroleum solutions.
b) Lead, tin, and their alloys find some use as engineering materials. Both are mechanically
soft and weak, have low melting temperatures, are quite resistant to many corrosion
environments, and have re-crystallization temperatures below room temperature. Many
common solders are lead–tin alloys, which have low melting temperatures. Applications for
lead and its alloys include x-ray shields and storage batteries. Tin is used as a very thin
coating on the inside of plain carbon steel cans (tin cans) that are used for food containers;
this coating inhibits chemical reactions between the steel and the food products.
c) Zinc is a relatively soft metal having a low melting temperature and a re-crystallization
temperature. Chemically, it is reactive in a number of common environments and, therefore,
susceptible to corrosion. Galvanized steel is just plain carbon steel that has been coated with a
thin zinc layer; the zinc preferentially corrodes and protects the steel .Typical applications of
galvanized steel are familiar (sheet metal, fences, screen, screws, etc.). Common applications
of zinc alloys include padlocks, automotive parts (door handles and grilles), and office
equipment.
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d) Zirconium and its alloys are ductile and have other mechanical characteristics that are
comparable to those of titanium alloys and the austenitic stainless steels. However, the
primary asset of these alloys is their resistance to corrosion in a host of corrosive media,
including superheated water. Furthermore, zirconium is transparent to thermal neutrons, so
that its alloys have been used as cladding for uranium fuel in water-cooled nuclear reactors.
3.1.4.9 NON-METALLIC MATERIALS
These are the materials that do not exhibit metallic characteristics in their properties.
Examples are composites, ceramics, rubbers, plastics and polymers.
3.1.4.9.1 POLYMERS
These are compounds of high molecular weight derived by the addition of smaller molecules
(monomers) or by the condensation of smaller molecules with the elimination of water,
alcohol and other solvents. There are many different polymeric materials that are familiar to
us and find a wide variety of applications.
3.1.4.9.2 Plastics
They have a wide variety of combinations of properties. Some plastics are very rigid and
brittle; others are flexible, exhibiting both elastic and plastic deformations when stressed, and
sometimes experiencing considerable deformation before fracture. Plastic materials may be
either thermoplastic or thermosetting.
A. Thermoplastics
These are also known as thermo softening plastics. They have very weak Van Der Waals
forces. They are polymers that liquefy on heating and when cooled, they form a very glassy
state. They are easily moulded and extruded into films, fibres and packaging materials. E.g.
Polyvinylchloride, polyethylene
B. Thermosetting plastics
These are polymers that cure irreversibly. Once cooled and hardened, they return to their
shapes but cannot return to their original form. The curing is by heating or through a
chemical reaction. They can be used for automobile parts, aircraft parts and tyres. Examples
are vulcanized rubber and epoxy resins.
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3.1.4.9.3 Elastomers
They have a cross linked structure with a looser mesh than thermosets. Thus they have the
ability to be deformed to quite large deformations, and then elastically spring back to their
original form. Their moduli of elasticity are quite small. They are to produce automobile
tyres. Example is Natural poly-isoprene (natural rubber)
3.1.4.9.4 Fibres
Fibres are capable of being drawn into long filaments (100: 1 length-to-diameter ratio). Fibre
polymers are utilized in the textile industry, being woven or knit into cloth or fabric. While
in use, fibres may be subjected to a variety of mechanical deformations: stretching, twisting,
shearing, and abrasion. Consequently, they must have a high tensile strength (over a
relatively wide temperature range) and a high modulus of elasticity, as well as abrasion
resistance.
3.1.4.9.5 CERAMICS
These are inorganic non-metallic materials made up of two or more elements bonded
together. They can be dense or light in weight but with excellent strength and hardness
properties. Typical properties of ceramics include:




Ceramics are brittle, wear resistant, hard and oxidation-resistant.
They are very strong in compression but very weak in tension due to presence of
minute cracks.
They are also widely applicable in positions involving chemicals because they are
inert.
Ceramics are hard and strong.
Ceramics are divided into four sections of application, namely:Structural application ceramics e.g. bricks, roof and floor tiles.
Refractory applications: These are the ceramics used as kiln linings and gas fire radiant.
Technical engineering applications: These include fire ceramics used in space shuttle
programmers.
White ware applications ceramics: They become white after the high-temperature firing e.g.
porcelain, pottery, tableware, china, and plumbing fixtures (sanitary ware).
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3.1.4.9.6 COMPOSITES
These are engineering materials made from two or more materials with significantly different
chemical and physical properties and these materials remain separate or distinct on the
microscopic level within a finished structure. The constituent material is either a matrix or
reinforcement.
The matrix, usually a polymer matrix, surrounds and supports the reinforcement by
maintaining their relative positions. The reinforcement; usually fibres, metals, ceramics and
polymers impart their mechanical and physical properties to enhance the matrix properties.
Composites have special properties like:
Fire resistance.

Light weight.

Chemical and weathering resistance.

Good electrical properties.

High strength to weight ratio.
Composites fail by: Shock, impact and repeated cyclic loading causing separation of the
layers (de-lamination). Some composites are brittle and have little reserve strength beyond
initial onset of failure while others have reserve energy absorbing capacity past the onset of
damage. In comparison with other materials, composites have poor bearing strength.
3.1.4.10 SEMI CONDUCTORS
These are the materials which have electrical properties that are intermediate between the
electrical conductors and insulators. The electrical characteristics of semiconductors are
extremely sensitive to the presence of minute concentrations of impurity atoms; these
concentrations may be controlled over very small spatial regions. Semiconductors form the
backbone of electronic industry. The semiconductors have made possible the advent of
integrated circuitry that has totally revolutionized the electronics and computer industries.
They affect all walks of life whether it is communications, computers, biomedical, power,
aviation, defence, entertainment, etc. The field of semiconductors is rapidly changing and
expected to continue in the next decade. Organic semiconductors are expected to play
prominent role during this decade. Diamond as semiconductor will also be important.
Optoelectronic devices will provide three-dimensional integration of circuits, and optical
computing.
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3.1.4.11 BIOMATERIALS
These are employed in components implanted into the human body for replacement of
diseased or damaged body parts. Biomaterials must not produce toxic substances and must be
compatible with body tissues (i.e., these materials must not cause adverse biological
reactions). All the above materials, i.e., metals, ceramics, polymers, composites, and
semiconductors—may be used as biomaterials.
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4
CHAPTER FOUR
4.1
REVIEW OF LITERATURE ON DECISION THEORY AND INFORMATION
PROCESSING
Engineering design in general, and the selection of engineering entities, in particular, is
largely a decision making process. Prudent decision making should preferably be based on
adequate information and therefore the decision making process often involves the processing
of available data into information that can be readily used to make the decisions. The theory
of decision making codifies the logic of rational action in situations in which one’s
knowledge is limited. The usual limitation is a lack of a reliable basis on which to know or to
estimate the objective probabilities of various states of the world. In decision making
situations three elements are of importance; action, states and outcomes. Actions are the
alternative ways of acting available to the deliberator. States are ways the world might be.
Outcomes are the anticipated consequences or effects of each action if a particular state
occurs.
4.1.1 DECISION THEORY
4.1.1.1 INTRODUCTION
Decision theory deals with methods for determining the optimal course of action when a
number of alternatives are available and their consequences cannot be forecast with certainty.
Decision theory can be classified into:
•
Descriptive decision theory, which is concerned with the ways in which people
actually make decisions and the mechanisms underlying this behaviour.
•
Normative decision theory, which is concerned with the principles that form the basis
of rational decision making.
Furthermore, under normative decision theory, decision problems can be classified into
decision problems without uncertainty and decision problems with uncertainty (Mendoza and
Gutierrez-Pena, 2010).
Decision Problems without Uncertainty
In a decision problem, the decision-maker is required to select one and only one action from
the set of possible actions. A = {a1,a2 ,….,ak}. Every action in A is judged according to the
consequence that it will lead to, if selected. Therefore, associated with A will be the set of
consequences, C ={c1, c2,….,ck, } where ci is the consequence that is associated with action
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ai. If for every action the corresponding consequence is completely known and definite, such
that it occurs every time the action is taken, then we have a decision problem without
uncertainty. Under these circumstances, the best action will be that which leads to the most
preferred consequence. Therefore, the decision-maker must, in some way, express their
preferences among the elements of C. This is will be our main area of focus during this
project.
Decision Problems under Uncertainty
Often, once an action has been chosen, there will be a set of possible consequences associated
with it. Among these possible consequences, one and only one of them will take place,
depending upon the occurrence of some uncertain event. This means that the decision has to
be made under uncertainty. This kind of decision problem is mentioned here only for
completeness and shall not be elaborated further.
The Analytic Hierarchy Process (AHP)
AHP is a tool that is used in decision making without uncertainty and is designed for
situations in which the relative importance of the factors that affect the decision process are
quantified to provide a numerical scale for prioritizing the alternatives (Taha,2008). In a
given decision problem, suppose that the set of possible courses of action is
A = {a 1,a2,a3,….,am}.Further, suppose that a set of factors F = {f1, f2 , f3,….fn}upon which the
decision is to be based has been established and that the intention is to establish a normalized
set of weights W = {w1,w2 ,w3,….,wn}to be used when comparing the relative importance of
these factors in the decision making process. Suppose too that a set of numerical values Bi
={bi1,bi2 ,bi3,….,bin}can associated with each course of action. If the elements of Bi are
appropriately coded such that they are positive real numbers whose values, in some suitable
way, indicate the utility associated with the set of factors F , we can calculate the utility
functions u(ai) , as follows:
The course of action to be preferred will then be the one that returns the highest value of the
utility function. In an attempt to establish the set of normalized weights, W, an n by n
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pairwise comparison matrix V can be formed, in which the element vijgives the relative
importance of fi as compared with f j.If by definition the elements of the pair wise comparison
matrix V are as follows:
Then it follows that;
The matrix V is then said to be reciprocal. Moreover, it also follows
In the above equation, n is the principal eigen value, and W the principal eigenvector of V
Furthermore, if the matrix V is to be consistent, for any i,jand k , the following relationship
must hold
In practice, the decision maker starts by assigning values of vijbased on their judgment and
experience, as a first estimate of V . Then the matrix V that is so obtained can be checked for
consistency by computing a consistency index. The procedure for doing this can be found in
Taha (2008) and Saaty (1990) among others. If the first estimate of Vis found to be too
inconsistent, an attempt can be made to improve it and the whole procedure be iterated. If all
the factors are judged to be equally important, as can very well happen in a mechanical
design situation, then vij= 1 for all iand all j , and the resulting matrix V will be consistent.
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4.1.2 INFORMATION PROCESSING
Information processing can be classified into the following four categories of activities:
•
Preparation and input of data,
•
Processing of data into useful information,
•
Storage and retrieval of information,
•
Reporting and communication of information.
When these four categories of activities are linked together, they may be regarded as a cycle
in which data is processed into information.
Information is taken as a sequence of symbols from an alphabet for example an input
alphabet X, and an output alphabet Y. Information processing consists of an input-output
function that maps any input sequence from X into an output sequence from Y. The mapping
maybe probabilistic or determinate .The information maybe in the form of text, tables,
graphs, photographs, computer programs, or video clips. It can be large in quantity and
detailed, specific and precise in nature. The most common medium for such data is
manufacturers' leaflets and catalogues, information which, increasingly, is becoming
available in electronic form – in databases, on CD–ROMS, and on the Internet. Typically, a
database of supporting information contains data of the following types:
•
Reference information about the entity and others like it;
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•
Examples of the use of an entity, or of engineering systems which contain it;
•
Design guidelines and standards relevant to the use of the entity;
•
Case studies and worked examples;
•
References to other sources of information, including scientific and engineering
literature, and suppliers’ information.
The advantages of such computerized sources are that:
•
The person(s) who compile the database often improve the consistency of the data.
•
The information can be updated regularly and easily.
•
The programs can be quicker and more convenient to use than handbooks.
•
They can provide links between attributes (property data) and other information.
Currently, however, they also have certain disadvantages:
•
Each disk uses different terminology, standards and format.
•
They are often class-specific, with manufacturer’s 'spin' on the information.
•
Data on the disks often lags behind printed publications.
•
Selection facilities can be rudimentary.
•
False conclusions can be drawn if the database and searching algorithm are badly
structured.
The Internet contains an expanding spectrum of information sources. Some, particularly those
on the 'World-wide Web' (WWW), contain data for materials, for processes, for components
and for products. The information is provided by standards organizations, trade associations,
learned societies, universities, and individual manufacturers or suppliers, who provide
information about their specific product ranges.
The main advantages of the WWW include;

The direct and timely access to supplier and economic information.

Powerful links between sites.

The uniform, machine-independent, program interface.
The main disadvantages are that it:

Can be difficult and time consuming to find information.

There are no uniform standards, designations or units.

Selection strategies differ from site to site.

There is no formal control over the quality of the information.
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5. CHAPTER FIVE
5.1. CASE STUDY: DESIGN AND SELECTION OF WIRE ROPE
MATERIAL FOR A MANUAL WINCH
5.1.1. INTRODUCTION
5.1.1.1.
Definitions
A winch is a mechanical device for hoisting or hauling. Essentially, it consists of a rotating
drum around which a cable is wound so that rotation of the drum can produce a drawing force
at the end of the cable. When the winch is manually powered then it is known as a manual
winch.
Fundamentally, we need to select a suitable flexible hauling/hoisting appliance for our
purpose, which in our case is a wire rope.
Terminology
Since wire rope take on several different configurations and are used for many different
purposes, several different definitions are in common use, as listed below. The nomenclature
is not always clear cut and there is often an overlap of function and therefore of definition.
The following are some terminologies:
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AIRCRAFT CABLES – Strands and wire ropes made of special strength wire
originally used primarily for aircraft controls and miscellaneous uses of aircraft
industry.
CLOSED SOCKET – Wire rope and fitting consisting of basket and bail made
integral.
CONSTRUCTION – Design of wire rope including number of strands, number of
wires per strand and arrangement of wires in each strand.
CORE – Member of a wire rope about which the strands are laid. It may be fiber, a
wire strand or an independent wire rope.
CORRUGATED – Term used to describe the grooves of a sheave or drum when worn
so as to show the impression of a wire rope.
DIAMETER – Distance measured across the center of a circle circumscribing the
wires of a strand or the strands of a wire rope.
GALVANIZED ROPE – Rope made of galvanized wire.
GRADES, ROPE – Classification of wire rope by its breaking strength. In order of
increasing breaking strengths they are Iron, Traction, Mild Plow Steel, Plow Steel,
Improved Plow Steel, and Extra Improved Plow Steel.
GRADES, STRAND – Classification of strand by its breaking strength. In order of
increasing breaking strengths they are Common, Siemens Martin, High Strength and
Extra-high Strength. A Utilities grade strand is also made to meet special requirement.
INNER WIRES – All wires of a strand except surface or cover wires.
INTERNALLY LUBRICATED – Wire rope or strand having all wires coated with
lubricant.
IWRC – “Independent Wire Rope Core”.
LANG LAID ROPE – Wire rope in which the wires in the strands in the rope are laid
in the same direction
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LAY – Manner in which wires are helically laid into strands or strands into rope.
LEFT LAY – (a) Strand – Strand in which the cover wires are laid in a helix having a
left-hand pitch; (b) Rope – Rope in which the strands are laid in a helix having a lefthand pitch.
MOORING LINES – Galvanized wire rope, usually 6 x 12, 6 x 24or spring lay
construction, for holding ships to dock
OPEN SOCKET – Wire rope fitting consisting of a “basket” and two “ears” with a
pin.
SUPER-FLEX SLINGS – Several wire ropes helically laid by machine form sling
body of3, 4, 5, 7 or 9 parts. Offer higher rated capacity than hand formed slings.
Flemish-type splices and mechanically pressed sleeves form eyes, providing
“centerline” pull. High flexibility. Every sling proof tested.
BRAIDED SLINGS - One or more wire ropes are braided to provide wide bearing
surface in the body. Very flexible and capable of bending in tight radius to “snug up
tight” around loads. 5, 6 and 7-part slings have flat bodies, 8-part is round.
PREFORMED WIRE ROPE – Wire rope in which the strands are permanently
shaped, before fabrication into the rope to the helical form they assume in the wire
rope
REEL – The flanged spool on which wire rope or strand is wound for storage or
shipment
REGULAR LAID ROPE – Wire rope in which the wires in the strands and the strands
in the rope are laid in opposite directions
REVERSE LAY – Synonymous with “Alternate Lay”
ROTARY LINES – The wire rope on a rotary drilling rig which raises and lowers the
traveling block
SOCKET – Type of wire rope fitting. See “Closed Sockets,” “Open
Sockets” and “Wedge Sockets”
STAINLESS STEEL ROPE – Wire rope made of chrome-nickel-steel wires having
great resistance to corrosion
STRENGTH, NOMINAL – Published catalog strength which has been calculated and
accepted by the wire rope industry following a set standard procedure. The wire rope
manufacturer uses this strength as a minimum strength when designing the wire rope
and the user should consider this to be the strength when making his design
calculations
STRENGTH, ACCEPTANCE – Strength which is 2-1/2% lowers than the nominal
strength. This variance is used to offset possible variables which might exist when the
test is made to determine the breaking strength of a specific piece of wire rope. Its use
originated with the basic government wire rope specification
STRENGTH, BREAKING – Load, applied through some type of tensile machine that it
takes to pull that piece of rope apart. This is the load at which a tensile failure occurs
in the piece of wire rope being tested
STRENGTH, AGGREGATE – Sum of the breaking strength intension of all the wires
of a wire rope when the wires are tested individually
THIMBLE – Grooved metal fitting to protect the eye of a wire rope
WEDGE SOCKET – Wire rope fitting in which the rope is secured by a wedge
WIRE ROPE – A plurality of strands lay helically around an axis or a core
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HAND LAID & SPLICED SLINGS -Fabricated from one or more wire ropes helically laid
together continuously through both eyes and sling body. Rope ends secured by hand-tucked
splices. High flexibility, conform well to irregular loads, snug load tighter in choke hitch and
easier to pull from under loads than mechanically spliced eyes.
CABLE LAID SLINGS -These smooth, clean slings are made from a rope-like fabric formed
by laying 6 wire ropes in a helical pattern around a core rope. Flemish splices secured by
pressed sleeves provide “centerline” pull at eyes. More flexible than same capacity singlepart slings.
5.2 WIRE ROPE
An example of a wire rope is as shown.
Figure 5.1A preliminary drawing of a wire rope drawn for design purposes.
Wire rope and cable are each considered a “machine”. The configuration and method of
manufacture combined with the proper selection of material when designed for a specific
purpose enables a wire rope or cable to transmit forces, motion and energy in some
predetermined manner and to some desired end.
The term cable is often used interchangeably with wire rope. However, in general, wire rope
refers to diameters larger than 3/8 inch. Sizes smaller than this are designated as cable or
cords.
Two or more wires concentrically laid around a center wire are called a strand. It may consist
of one or more layers. Typically, the number of wires in a strand is 7, 19 or 37. A group of
strands laid around a core would be called a cable or wire rope. In terms of product
designation, 7 strands with 19 wires in each strand would be a 7x19 cable: 7 strands with 7
wires in each strand would be a 7x7 cable.
5.2.1 MATERIALS
Different applications for wire rope present varying demands for strength, abrasion and
corrosion resistance. In order to meet these requirements, wire rope is produced in a number
of different materials
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STAINLESS STEEL
This is used where corrosion is a prime factor and the cost increase warrants its use. The 18%
chromium, 8%nickel alloy known as type 302 is the most common grade accepted due to
both corrosion resistance and high strength. Other types frequently used in wire rope are 304,
305, 316 and 321, each having its specific advantage over the other. Type 305 is used where
non-magnetic properties are required; however, there is a slight loss of strength.
GALVANIZED CARBON STEEL
This is used where strength is a prime factor and corrosion resistance is not great enough to
require the use of stainless steel. The lower cost is usually a consideration in the selection of
galvanized carbon steel. Wires used in these wire ropes are individually coated with a layer
of zinc which offers a good measure of protection from corrosive elements.
5.2.2 CABLE CONSTRUCTION
The greater the number of wires in a strand or cable of a given diameter, the more flexibility
it has. A 1x7 or a 1x19 strand, having 7 and 19 wires respectively, is used principally as a
fixed member, as a straight linkage, or where flexing is minimal.
Cables designed with 3x7, 7x7 and 7x19 construction provide for increasing degrees of
flexibility but decreased abrasion resistance. These designs would be incorporated where
continuous flexing is a requirement.
CONSTRUCTIO
N
DESCRIPTION
Basic strand for all concentric cable, relatively stiff in larger diameters,
offers the least stretch. Stiffest construction in small diameters.
Smooth outside, fairly flexible, resists compressive forces, strongest
construction in sizes above 3/32-inch diameter.
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Durable, higher flexibility and abrasion resistance. Good general
purpose construction for strength and flexibility. Can be used over
pulleys.
The strongest and most flexible of cables with greatest stretch.
Recommended for use over pulleys.
5.3 SELECTING WIRE ROPE
when selecting a wire rope to give the best service, there are four requirements which should
be given consideration. A proper choice is made by correctly estimating the relative
importance of these requirements and selecting a rope which has the qualities best suited to
withstand the effects of continued use.
The rope should possess:
Strength sufficient to take care of the maximum load that may be applied, with a proper
safety factor.
2) Ability to withstand repeated bending without failure of the wire from fatigue.
3) Ability to withstand abrasive wear.
4) Ability to withstand distortion and crushing, otherwise known as abuse.
1)
5.3.1 STRENGTH
Wire rope in service is subjected to several kinds of stresses. The stresses most frequently
encountered are direct tension, stress due to acceleration, stress due to sudden or shock loads,
stress due to bending, and stress resulting from several forces acting at one time. For the most
part, these stresses can be converted into terms of simple tension, and a rope of
approximately the correct strength can be chosen. As the strength of a wire rope is
determined by its, size, grade and construction, these three factors should be considered.
5.3.2 SAFETY FACTORS
the safety factor is the ratio of the strength of the rope to the working load. A wire rope with
strength of 10,000 pounds and a total working load of 2,000 pounds would be operating with
a safety factor of five.
It is not possible to set safety factors for the various types of wire rope using equipment, as
this factor can vary with conditions on individual units of equipment.The proper safety factor
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depends not only on the loads applied, but also on the speed of operation, shock load applied,
the type of fittings used for securing the rope ends, the acceleration and deceleration, the
length of rope, the number, size and location of sheaves and drums, the factors causing
abrasion and corrosion and the facilities for inspection.
5.3.3 FATIGUE
Fatigue failure of the wires in a wire rope is the result of the propagation of small cracks
under repeated applications of bending loads. It occurs when ropes operate over
comparatively small sheaves or drums. The repeated bending of the individual wires, as the
rope bends when passing over the sheaves or drums, and the straightening of the individual
wires, as the rope leaves the sheaves or drums, causing fatigue. The effect of fatigue on wires
is illustrated by bending a wire repeatedly back and forth until it breaks.
The best means of preventing early fatigue of wire ropes is to use sheaves and drums of
adequate size. To increase the resistance to fatigue, a rope of more flexible construction
should be used, as increased flexibility is secured through the use of smaller wires.
5.3.4 ABRASIVE WEAR
The ability of a wire rope to withstand abrasion is determined by the size, the carbon and
manganese content, the heat treatment of the outer wires and the construction of the rope. The
larger outer wires of the less flexible= constructions are better able to withstand abrasion than
the finer outer wires of the more flexible ropes. The higher carbon and manganese content
and the heat treatment used in producing wire for the stronger ropes, make the higher grade
ropes better able to withstand abrasive wear than the lower grade ropes.
5.3.5 EFFECTS OF BENDING
all wire ropes, except stationary ropes used as guides or supports, are subjected to bending
around sheaves or drums. The service obtained from wire ropes is, to a large extent,
dependent upon the proper choice and location of the sheaves and drums about which it
operates.
A wire rope may be considered a machine in which the individual elements (wires and
strands) slide upon each other when the rope is bent. Therefore, as a prerequisite to the
satisfactory operation of wire rope over sheaves and drums, the rope must be properly
lubricated. With this in mind, the effects of bending may be classified as:
a. Loss of strength due to bending.
b. Fatigue effect of bending.
Loss of strength due to bending is caused by the inability of the individual strands and wires
to adjust themselves to their changed position when the rope is bent. Tests made by the
National Institute of Standards and Technology show that the rope strength decreases in a
marked degree as the sheave diameter grows smaller with respect to the diameter of the rope.
The loss of strength due to bending wire ropes over the sheaves found in common use will
not exceed 6% and will usually be about 4%.
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The bending of a wire rope is accompanied by readjustment in the positions of the strands
and wires and results in actual bending of the wires. Repetitive flexing of the wires develops
bending loads which, even though well within the elastic limit of the wires, set up points of
stress concentration.
The fatigue effect of bending appears in the form of small cracks in the wires at these overstressed foci. These cracks propagate under repeated stress cycles, until the remaining sound
metal is inadequate to withstand the bending load. This results in broken wires showing no
apparent contraction of cross section.
Experience has established the fact that from the service view-point, a very definite
relationship exists between the size of the individual outer wires of a wire rope and the size of
the sheave or drum about which it operates. Sheaves and drums smaller than 200 times the
diameter of the outer wires will cause permanent set in a heavily loaded rope. Good practice
requires the use of sheaves and drums with diameters 800 times the diameter of the outer
wires in the rope for heavily loaded fast-moving ropes.
It is impossible to give a definite minimum size of sheave or drum about which a wire rope
will operate with satisfactory results, because of the other factors affecting the useful life of
the rope. If the loads are light or the speed slow, smaller sheaves and drums can be used
without causing early fatigue of the wires than if the loads are heavy or the speed is fast.
Reverse bends, where a rope is bent in one direction and then in the opposite direction, cause
excessive fatigue and should be avoided whenever possible. When a reverse bend is
necessary larger sheaves are required than would be the case if the rope were bent in one
direction only.
5.3.6 STRETCH OF WIRE ROPE
The stretch of a wire rope under load is the result of two components: the structural stretch
and the elastic stretch. Structural stretch of wire rope is caused by the lengthening of the rope
lay, compression of the core and adjustment of the wires and strands to the load placed upon
the wire rope. The elastic stretch is caused by elongation of the wires.
The structural stretch varies with the size of core, the lengths of lays and the construction of
the rope. This stretch also varies with the loads imposed and the amount of bending to which
the rope is subjected. For estimating this stretch the value of one-half percent, or .005 times
the length of the rope under load, gives an approximate figure. If loads are light, one-quarter
percent or .0025 times the rope length may be used. With heavy loads, this stretch may
approach one percent, or .01 times the rope length.
The elastic stretch of a wire rope is directly proportional to the load and the length of rope
under load, and inversely proportional to the metallic area and modulus of elasticity. This
applies only to loads that do not exceed the elastic limit of a wire rope. The elastic limit of
stainless steel wire rope is approximately 60% of its breaking strength and for galvanized
ropes it is approximately 50%. This may be expressed as:
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(Load in lbs.)(length of rope under load in feet)
elastic stretch (in feet) = ---------------------------------------------------------------------(Metallic area of rope in sq. in.)(modulus of elasticity)
5.4 WIRE ROPE SELECTION FOR MANUAL WINCH APPLICATION
The processing of information in the selection process can begin with the categorization
(sorting) of such appliances as given in Table 1
Based on experience, from among the community of flexible hoisting/hauling appliances,
wire rope types 6*19, 6 *37, and their variants are the more commonly used in such
applications as on manual winches. In the selection process, then, a quantitative screening of
rope types 6*19, 6*37, and their variants, shall be carried out in order to determine the
Suitable rope type for our particular application. Suppose that we have the set of
requirements R = {r1, r2, r3… r n}, that are to be met by the type of rope that we select.
Further suppose that we can assign weights W = {w1, w2, w3, L, wn}, which represent the
relative importance that we attach to each requirement. Given that there are m candidate types
of ropes to be screened, suppose that, for each type of rope, we have the set of n attributes or
properties, P ={ p1, p2 , p3,L, pn,} each of which should in some way, and to some extent,
satisfy a corresponding requirement, and each of whose value may be appropriately coded
bi1, bi2 , bi3,L, bin , for i= 1, 2, 3,L, m (for all rope types). We should then be able to
calculate indices of merit u( ) , for each type of rope, as follow:
Having found at least one type of rope to be suitable, in the next stage of selection, we will
scrutinize the attributes of each of the ropes within the selected types, vis-à-vis each
requirement upon the rope in order to finally select a suitable rope.
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Table 1. Taxonomy of the Community of Flexible Hoisting or Hauling Appliances
Wire Rope Selection Criteria and Property Ratings
Several factors have to be considered in the selection of a suitable wire rope for a given
application. The following factors usually need to be considered in most applications:
·Resistance to breaking,
·Resistance to bending fatigue,
·Resistance to abrasion,
·Resistance to crushing,
·Resistance to corrosion,
·Cost of the rope.
5.5 FAILURE IN ROPES WIRE
The followingis a summary of rope wire failure modes that have been identified during
examinations of wire ropes tested to failure on laboratory bending-fatigue machines. They are
characteristic of many field failures, but do not illustrate the effects of either abrasion or
corrosion. This discussion is derived from that in Reference 5-1, as are the figures.
5.5.1 MODE 1 FATIGUE FAILURES
Mode 1 wire fatigue failures, with the fracture surface criented about 45 degrees to the
longitudinal axis of the wire, have failure initiation sites located at a point of contact with
adjacent wires. Some Mode 1 failures are found to initiate at points of inter-strand contact.
Typical failures of this type are shown in Figures 2-1 and 2-2.
Mode 1 failures are also found with the initiation sites at parallel-wire marks, as shown in
Figure 2-3. Examination of the Mode 1 fatigue failures reveals a 45 degree shear failure with
no obvious evidence of fatigue. The shear failure results from overload and the orientation of
the plane of failure is a result of the multi-axial stress state at the point of inter-wire contact
(combined contact, tension and bending loads). Mode 1 failures have been produced in the
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laboratory under simulated loading conditions with a single application of load. This failure
mode also occurs under slightly lower cyclic wire loads as a result of reduction in wire area
because of the deepening notch wear scat, Or because of small surface fatigue cracks
perpendicular to the wire axis. Some possible minute fatigue crack initiation sites at the point
of inter-wire contact are observed under high magnification in many of the failures.
Mode I failures are predominant in high-load tests on laboratory bend-over sheave wire-rope
fatigue machines.
5.5.2 MODE 2 FATIGUE FAILURES
Mode 2 fatigue failure exhibits the more usual characteristics of a fatigue failure. Each
fatigue crack propagates on a plane perpendicular to the longitudinal axis of the wire, and the
characteristic "clam shell" or "beach" %arks are present. No evidence of plastic flow or
reduction of area is found at the failure sites. The cracks initiate at the points on the wires that
experience the maximum combined tensile, bending, and contact stresses.
Mode 2 failures are the most common type found in ropes operating on hard sheaves under
moderate conditions (within recommended practice). In these cases, the fatigue crack initiates
at a point opposite the wire-sheave contact and propagates toward it. These breaks obviously
occur in the outside, or crown wires, that contact the sheave.
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Failures of this type are found to initiate on the as-drawn surface of the wires in areas not
associated with points of inter-wire contact. On aluminum sheaves, these fatigue cracks
appear on the outer surface of the wire rope well away from points of inter-strand contact.
This type of failure is illustrated in Figure 2-4. The inner wires of the strands often display a
similar type of failure, with the fatigue crack initiating between two parallel-wire marks as
illustrated in Figure 2-5. Both of these Mode 2 fatigue failures are found after low-load tests
on laboratory fatigue machines. For many Mode 2 failures, each fatigue crack propagates into
the wire until the reduction in metallic area and the stress concentration at the crack root
result in complete fracture. The lower the tensile load on the specimen, the further the cracks
propagate. Final failure may then be either a tensile-type failure displaying a rather rough
fracture surface approximately perpendicular to the wire axis, or a shear-type failure
displaying a rather smooth fracture surface about 45 degrees to the wire axis. Examples of
each of these failures are shown in Figures 2-6 and 2-7. Sometimes a Mode 2 failure is
accompanied by a longitudinal splitting of the wire as shown in Figure 2-8. This wire
splitting occurs more frequently at the lower test loads. Another type of Mode 2 fatigue
failure has been identified in wire-rope specimens where there is severe inter-wire notching.
For these failures the fatigue cracks are found to initiate at the edge of a wire notch formed by
inter-strand contact as shown in Figure 2-9. Photographs of typical wires displaying this
failure mode are shown in Figures 2-10 and 2-11. Mode 2 fatigue cracks can also initiate on
the side of the wire opposite the notch at or near the parallel-wire marks and propagate
toward the notch. Examples of these failures are shown in Figures 2-12 and 2-13.
5.5.3 TENSILE FAILURES
During any type of wire-rope fatigue test, the wires begin to fail by one of the abovementioned fatigue modes. The strength of the rope is gradually reduced until complete failure
of a strand or strands results from tensile overload of the remaining wires. Some of these
tensile failures display a standard cup-cone type of failure.
The fracture surface of the cup-cone tensile failure is symmetrical and exhibits large shear
lips around the outer edge of the wire and creates the typical "cup" and "cone" as shown in
Figure 2-14. The nominal orientation of the fracture surface is perpendicular to the
longitudinal axis of the wire, and a large reduction of cross-sectional area is found at the
fracture location. Failures of this type are typical of low-strain-rate round-bar tensile failures
of a ductile material
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Sometimes rope wires that fail by tensile overload display tensile failures similar to those
observed in high strain-rate overload experiments on simple tensile specimens of a ductile
material, the failure differs from the low-strain- rate cup-cone failure in that a smaller
reduction of metallic area is observed. Also, the fracture surface is more irregular and does
not possess the symmetry of the cup-cone failure. This type of fracture is shown in Figure 215.
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5.6. TORQUE CALCULATION
The following presents the derivation of equations for computing the torque which develops
due to loading for most common wire-rope constructions. In general, a wire rope is made up
of a layer or layers of strands helically wrapped around a metallic or fiber rope core. The
strands itself comprises a layer or layers of wires helically wrapped around a wire or fiberstrand core. The basic assumptions that are used in this analysis include the following:
1.The rope is loaded in tension only with the ends held fixed to prevent twisting or unlaying
of the strands.
2. All stresses in the wires remain below the elastic limit of the material and the material
obeys Hooke's Law.
I
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3. Radial dimensions for the cross section of the unloaded rope are assumed to remain
constant under load; the inter-wire contact deformations and rope-core compression are
neglected,
4. All strands in each layer are the same length and are formed into perfect helices.
5. All wires in all strands are made of the same material.
6. All wires in each layer of each strand are the same length and are formed into perfect
helices before closing the strands the into a rope.
7. Values for the tensile stresses in the individual wires and the torque developed by the wires
as calculated for straight strands are assumed to be valid for strands helically wrapped to
form a wire rope.
Basically, the analysis developed below shows the total wire-rope torque to be the
summation of strand torque and wire torque, with the direction of twist of the strands and
wires providing the appropriate sense of the signs for the summation.
5.6.1General Theory for Analysis of Wire-Rope Torque
Consider first the simple wire-rope geometry shown in Figure 3-46 where N strands are
wrapped in a right-hand helix around a fiber core. As shown in Figure 3-47, the tensile load
on each strand is
The tensile load, T, on the wire rope produces for each strand a driving force,
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which acts to unlay the strand. The total moment produced in the rope owing only to the
helical wrap of the strands is then
as determined by Figure 3-48. Substitution of Equations 3-3 and 3-4 into Equation 3-5 yields
which is positive for a right-hand rope lay. Equation 3-6 is valid for any rope with a single
layer of strands wrapped around a fiber core. This includes flattened-strand as well as roundstrand3-44
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strand core, the calculation becomes only slightly more complicated as will ) be discussed
later. Consider now a single strand under a tensile load T. This strand is composed of m
layers of wire wrapped around either a fiber core or a wire core, all wires being made of the
same material, as it has been shown that the tensile stress in the core wire may be calculated
using the equation,
The tensile stress on the wires in any layer may then be found by
If the strand has a fiber core rather than a metallic core, Equation 3-7 may still be applied by
setting Ac equal to zero. The resulting numerical value, although it has no physical meaning,
may then be used with Equation 3-8 to determine the actual stress ip the other wires. Tn
general, the tensile stress in the wires in the it' layer is related to the tensile stress in the wires
in the jthlayer by
Equation 3-8 is a special case of Equation 3-9 where arc = 0. The torque induced in the strand
by the tensile load may be calculated usingthe same procedure as outlined in Equations 3-3
through 3-6. The forceacting to unlay one wire is
as determined by Figure 3-.,•. The total moment contribution of one complete layer of strands
due only to the helical wrap of the wires is then
or, by substitution of Equation 3-10,
which is positive for a right-hand-strand lay. The total torque developed in a simple wire rope
with a fiber core may now be expressed as the sum of the contributions of the helically
wrapped strands and the helically wrapped wires, or
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For a wire rope with more than one layer of strands, the above equations for torque and wire
stress must be solved by taking one layer of strands at a time. The torque produced by the
helically wrapped strands is calculated using an expanded version of Equation 3-6,
where T1 is the portion of the rope tension that is carried by the ith layer of strands. To
calculate T,, Equation 3-7 must be solved for each layer of strands to find the core-wire stress
in terms of the tension carried by that layer of strands. Then, if all core wires are made of the
same material, Equation 3-9 applied to the strard-core wires yields, as a special case
Simultaneous solution of Equations 3-3, 3-7, and 3-15 gives the desired values for T1 . This
same analysis applies to ropes with a strand core, ropes with an independent wire-rope core,
or multiple-layer non-rotating ropes. If the strand wires are not all of the same material,
Equation 3-9 must be further modified to include the appropriate elastic moduli,
Calculation of the torque contribution of the helically wrapped wires in a complex rope
requires the application of Equation 3-12 to each layer of strands. Again, all values of torque
are positive for right-hand lay. This same analysis may be applied to flattened-strand ropes,
although the wires in such ropes do not have constant pitch radii. By assuming an average
value for the pitch radius of the wires in each layer, fairly -% accurate results are obtained.
The analysis presented in this paper applies only to wire ropes having the F ends fixed to
prevent twisting or unlaying of the strands. Any amount of _ rotation drastically alters the
stress distribution in the rope, especially in non-rotating rope constructions. The above
equations provide a method of determining the magnitude of the wire stresses and torque that
will be developed by almost any wire rope. However, these calculations are time consuming,
especially for ropes containing strands with several layers of wires. A simplification that
provides a more convenient method for calculating wire stress and wire-rope torque is
discussed below.
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5.6.2Simplified Equations for Wire Ropes with Single-Operation Strands
Majorities of the wire ropes in common use are composed of single-operation strands, that is,
strands that are fabricated in one pass through the stranding machine so that all wires have the
same lay length or pitch.
The following analysis applies to ropes with single-operation strands. In Equation 3-7, (n. A,)
equals the total area of all wires in the ith layer of the strand. This may be replaced by k
(2nr,)dw wide as shown in Figure 3-50, and k is a constant used to account for the fact that a
layer of wires has a smaller total area than a ring of the same width. Equation 3-7 then
becomes
Now suppose the number of wires in the strand is allowed to become very large, and at the
same time the size of each wire is allowed to become very small, for a strand in which all
wires have the same lay length, Equation 3-17 may be expressed as
From the strand geometry, it is found that 2n = A tan ∝ . Also dr = (L/2.)
Substitution of these relationships into Equation 3-18 gives
α dα.
Where
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The solution to Equation 3-19 is
This equation may be used to calculate the tensile stress in the core wire for any singleoperation strand in which all wires have the same lay length, A. It has been found that a value
for k of 0.80 provides a good approximation for most common strands. The stress in the
layer of wires may then be found using Equation 3-8.
A similar technique may now be used to evaluate the torque provided by the helically
wrapped wires in one layer of strands. In Equation 3-12, let
and
The total torque developed by the wires in one layer of strands is then
The solution of Equation 3-22 is
Substitution of Equations 3-3 and 3-21 into Equation 3-23 gives the total torque contribution
of all wires in one layer of strands,
It has been found that for common wire-rope geometries, Equation 3-24 yields values of wire
torque approximately 10 percent higher than the torque calculated using Equation 3-12. This
influences the value of the total wire rope torque by only about 2%.
Now the total torque developed by a simple fiber-core wire rope under tensile load T may be
expressed as
Again, if a complex (multiple-layered) wire rope is being considered, simplified Equations 320, 3-21, and 3-24 must be applied to each separate layer of strands as was discussed earlier
with regard to Equations 3-6, 3-7, and 3-12.
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5.6.3Simplified Equations Applied to Six-Strand Wire Ropes
Probably the most common wire-rope construction consists of six strands wrapped around a
fiber core. The simplified equations may be conveniently expressed graphically for this type
of wire-rope construction. For either round-strand or flattened-strand ropes, a good value for
the pitch radius of the strands is
R = 0.34 d
(3-26)
Accordingly, the strand diameter is about
= 0.32 d
(3-27)
The use of Equation 3-26 in conjunction with Equation 3-6 yields the torque contribution of
the helically wrapped strands in a six-strand rope as
Figure 3-51 provides a graphical representation of Equation 3-28 and includes values for the
strand lay angle, S. Logarithmic coordinates are used in this figure to provide reasonable
accuracy over a wide range of wire-rope geometries. Equation 3-28 or Figure 3-51 may be
used for six-strand ropes with either single-operation or multiple-operation strands. The
tensile stress in the core wires of a six-strand wire rope may be calculated using Equation 327 together with Equations 3-20 and 3-21. This yield
where
The tensile stress in any other wire in the strand may be calculated using Equation 3-8. The
tensile stress is highest in the core wire and it is lowest in outer wires of the strand. For most
common ropes, the outer wires are stressed to at least 90 percent of the stress in the core wire.
Equation 3-30 may now be used with Equation 3-24 to evaluate the total torque contribution
of the helically wrapped wires in a six-strand wire rope composed of single-operation strands.
The result is shown graphically in Figure 3-52.
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The data displayed in Figures 3-51 and 3-52 may now be used directly as indicated by
Equation 3-25 to evaluate with suitable accuracy the total torque developed by a simple wire
rope containing six single-operation strands.
5.6.4Sample Calculations for Simple Wire Rope
As an example of how the simplified equations may be used to advantage, consider the wirerope geometry shown in Figure 3-53. A 1-3/8-inch-nominaldiameter,
Lang-lay rope of this design was tested to determine the torque developed as the specimen
was loaded with the ends restrained from rotation. A sensitive strain-gage load cell was used
to monitor both tension and torque as the rope was loaded a number of times to 100,000
pounds or about 60 percent of its breaking strength. The torque curve was found to be linear
with 0.204 inch-pounds of torque developed per pound of applied tension.
The actual diameter of this preformed rope was d = 1.41 inches, the rope lay was L = 8.80
inches, and the strand lay was = 3.74 inches. These are the only three parameters for which
values must be known to make use of the simplified equations developed above.
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From Equati'a 3-28 or Figure 3-51, the torque contribution of the helically (. wrapped strands
is found to be Ms = 0.164 T inch-pounds. Using Equations 3-29 and 3-30, the stress in the
core wire is found to be 0c = 8.73 Ts psi. Equations 3-24 and 3-30 or Figure 3-52 gives the
total torque contribution of the helically wrapped wires as Mw= 0.041 T inch-pounds. The
total torque produced in the wire rope is then M = Ms + = 0.205 T inch-pounds, which is
essentially identical to the measured value of 0.204 T inch-pounds. If the same calculations
are attempted using the longer method of analysis, it is necessary to first makes the
measurements and calculations indicated in Table 3-6. Here the wire stress is determined
using Equations 3-7 and 3-8. The value obtained in this way for core-wire stress is within 2
percent of the value calculated using the simplified analysis.
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Table 3-6. MEASUREMENTS AND CALCULATIONS FOR EXAMPLEN WIRE-ROPE
CONSTRUCTION
Using equation 3-12, a value for contribution of the helically wrapped wires if found to be
Mw = 0.037 T inch-pounds. This is approximately 10 percent lower than the value obtained
using the simplified analysis. The total torque produced in the wire rope is then M = Ms+ N,
= 0.201 T inch-pounds, which is within 2 percent of the measured value. These sample
calculations indicate that both methods of analysis provide accurate values for wire-rope
torque. The real value of the simplified analysis is that it may be used to determine the torque
characteristics of a working six-strand wire rope by measuring only the rope diameter, d; the
rope lay, L; and the strand lay, l.
5.6.5Measurement of Rope Lay and Strand Lay
Measurement of the rope lay can be done quire accurately by following strand along the rope
for a number of turns and then dividing that length of the rope by the number of the strand.
Measurement of the strand lay can also be made quite accurately if the number of outer wires
in each strand is known. This may be done by placing a length of tape helically on the rope so
that it follows along one strand for exactly one turn around the rope. If the tape is then rubbed
with a pencil lead or other marker, an image of each wire will be left on the tape. This tapemeasuring technique for determining strand lay may be expressed as follows:
Where
In Equation 3-31 the positive sign is used for Lang-lay wire rope and the negative sign is
used for regular-lay wire rope.
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The correction factor, C, used in Equation 3-31 is required for the following reason. In one
rope lay, the true length of the strand as measured at the strand centerline is S = L/cos S,
where B = tan-r (2rRL). The strand length as determined by the tape-measuring technique
will be S' = L/cos β', where β' = tan-' (πd/L). The value of S' is larger than the value of S.
Therefore, any physical measurement of strand length using the tape mist be multiplied by C
= S/S' = cos β'/cos θ to obtain values for true strand length.
5.7 RELATIVE STRAND MOTION IN A WIRE ROPE ON A SHEAVE
Wire rope is a complex machine element in which several important geometric changes take
place as a result of applied loads and bending around a sheave
or winding drum. The major changes in geometry of a straight wire rope in tension have been
investigated and are fairly well understood. The geometric changes occurring in a wire rope
on a sheave are less well understood. Among these changes are bending of the wires, shape
distortion of the cable due to the bearing load on the sheave, and relative motion between
adjacent strands and wires. An analysis of the relative motion between strands in a wire rope
on a sheave (Ref. 3-3) is considered below. The equation defining the strand length around
the sheave for a given wrap
angle, t, is:
where
Rp= pitch radius of sheave
R = pitch radius of strand, measured from rope to strand centerline, inches
¥ = sheave reference angle, degrees
θ = angle defining the position of a strand in a wire rope degrees
β= strand lay angle, degrees
θ = initial angular position of a strand, degrees
s = true length of one strand as measured from the point of rope to- sheave tangency through
any specified angle.
In the above equation θ determines which strand is being considered. Figure 3-54 shows the
graphical result of Equation 3-32 for a six-strand rope construction. The mathematical
analysis of this problem is presented in detail in Reference 3-3.
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5.8 WIRE ROPE STRESS ANALYSIS
A number of investigators discuss the difficulty or even the impossibility of accurately
computing the stresses in a wire rope. (Some of these same investigators then attempt the
analysis themselves with no better apparent success than those that preceded them.)
Nevertheless, efforts to derive equations that will permit a wire-rope designer to rationally
predict the relationship between the conditions imposed on a rope, the stresses produced, and
the resultant rope life continue. No one has succeeded to date primarily because of the
complex nature of the stress field present in the wires of a rope and its sensitivity to external
factors that are extremely difficult to identify accurately, such as friction and wire surface
condition. The induced stresses that are normally present in a loaded wire rope are tensile,
bending, shear, compressive, contact or "Hertzian", and torsion. To further complicate the
problem, there are normally residual stresses which have been introduced in the
manufacturing process. Both the construction of the rope and its usage conditions dictate
which of the stresses predominate.
In this presentation no attempt is made to give the derivation of the equations or all of the
assumptions that were made with the single exception of the bending stress analysis. The
interested reader should consult the cited references for more detailed analyses.
5.8.1 Tensile Stress
The tensile stress in an individual wire in a straight wire rope, neglecting radial contraction of
the rope under axial loading and internal friction, is given by (Refs. 3-35 and 4-2):
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5.8.2 Bending Stress
Over the years, many attempts have been made to compute (or estimate) the bending stresses
in a wire rope. These analyses have ranged from simplistic to extremely complex, many wirerope manufacturers and users regard the problem as insolvable. Indeed, until the advent of
large computers, the problem was nearly so. Currently, several attempts are in progress to
solve the problem using finite-element analysis techniques. Another analysis involving
methods of vector analysis and strength of materials has been completed and is reproduced
here.
To analyze the bending stresses in the wires of a rope, it is first necessary to determine the
radii of curvature of the wires prior to and after bending the rope. The wire-bending stress
can then be calculated from the change in wire curvature. The purpose of the following
analysis is to present a procedure for computing the radii of curvature of the wires both in a
straight rope and in a rope wrapped on a sheave and determining the resultant bending
stresses.
The complexity of the equations generated in the analysis requires numerical results in order
to be viewed meaningfully. Therefore, all numerical results were obtained using the
parameters of a 1-3/8-inch-diameter, 6 x 25 filler wire, Lang-lay, round-strand wire rope,
which is referred to hereafter as the Standard Rope.
Derivation of Equations.
Therefore, a stress relation for complex bending must be derived. Figure 4-15a displays a
segment of wire in the initially straight rope, where p, is the radius of curvature. The same
segment of wire, after bending of the rope, Figure 4-15b, has radius of curvature p..Figure 415c shows the relation between the initial and final positions of the wire, and Point N, the
maximum stress position in the new configuration. Denoting rw -s the wire radius and § as
the angle between P1 and p,, and assuming rw-< p1 or p., which allows use of simple beam
considerations in computing stress, the strain due to bending can be written as
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Figure 4-15 illustration of wire segments in complex Bending.
the length of that same segment as viewed by P2.Since the length of wire centerline in this
segment is unchanged,
Then, assuming the linear Hooke's Law stress-strain relation such that
where
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And substituting Equation 4-22 and 4-23 into 4-25, the result is
Then utilizing Equation 4-24,
or finally,
Assuming
cos .<< 1, an assumption justified by Figure 4-5, and knowing that
order of 0.05 inch, the result is,
is on the
The final point in the stress analysis concerns determination of angle ξ, the angle between
and . Noting that the radius of curvature is directed along the second geometrical
derivative , then the coordinates of the straight rope and the bent rope must be aligned such
that the angle between the second derivatives can be evaluated. An easy method to align
coordinates involves realizing that once values for Ф and θ have been specified in the bent
rope, then
is independent of φ, the reference angle in the sheave. This should be expected
since no unique values of φexist, although all values of θ and Ф in the bent rope are unique.
For example, a wire at position φ = 0, θ= 30, Ф=60. Has the same radius of curvature as
every other φposition where θ = 30, Ф= 60%. Thus, φneed not vary in the computer
program, but a specific convenient value such as φ= 0 can be chosen as the permanent sheave
position. This value of φ not only shortens the computer statements, but it also allows the
straight rope coordinate system to be placed at (Rp, 0, 0) such that the straight rope is always
tangential to the bent rope, Figure 4-16.
The coordinates are now aligned such that the Z coordinates of the straight rope correspond
to the X coordinates of the bent rope as
Where
, Xn ,
are the new X coordinates of the straight rope. Now as Ф and θ are
varied, the point whose radius of curvature is being considered is essentially always located
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in the - 3 plane. Therefore, points in the - 3 plane located by the same values of Ф and
θ are identical points. Dotting X" and Xn", the cosine of • can be found as
Figure 4-16. Coordinate Alignment Used for Comparing Radii-of-Curvature Results 4-27
It should be noted that since the plane in which Ф is measured angle is tilted at β to the 3 plane, the point under consideration can be as far as r sin β out of the plane. Then when
the rope is bent, the same point will not be at the same location and a slight error in ξ is
incurred. However, since for real rope and sheave parameters, R, <<R+ r, the error is so slight
that it can be completely ignored without loss of accuracy.
5.8.3 Contact Stresses
Contact stresses in a wire rope are one of the most important determinants of its fatigue life
and are, by far, the most difficult to analyze. To date, no reliable and accurate analysis has
been completed, primarily because these stresses, even under low rope tensile loads, are so
high that the wires yield, changing the geometry and thus invalidating the elastic forcegeometry-stress relationships normally used for stress computation. There are four areas in a
normal wire rope where contact stresses can be induced:
1. At the wire-sheave interfaces
2. At the interfaces between wires in a strand
3. At the interfaces between wires in adjacent strands
4. At the interfaces between the wires in the strands and the wires in the core of an IWRC
rope.
5.8.4 Torsional and Shear Stresses
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No published analysis of torsion stresses in a wire rope is known. One investigator has
derived equations for tensional stresses in strands but has not extended these to rope. The
importance of directly induced shear stresses, either torsion or longitudinal, is questionable
when the rope ends do not rotate (ends fixed or torque-balanced) thus preventing significant
rotational strain. As pointed out in the section on Failure Modes in Wire Rope, one
characteristic wire Failure mode is a typical 45-degree shear-type failure, but this type can be
(and probably is) induced by the complex combination of tension, bending, and compressive
contact stresses at the point of wire failure.
5.9 ROTATION AND TRANSLATION OF COORDINATES WITH MATRICES
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A convenient method of obtaining the new coordinates of a vector in an orthogonal system
whose axes are not parallel with the present system is that of pre multiplying the vector's
column matrix by 3 x 3 direction cosine matrices and adding translational column matrices
where appropriate. This technique is illustrated here for the purpose of obtaining the
coordinates of Point P in the Z system for the straight-rope analysis, and is not intended
to be a presentation of vector matrix theory,
The general form of the direction cosine matrix is
′
where
1 is the cosine of the angle between the new X' axis and the old X1 axis, etc., as
shown in Figure A-1.
Figure 5-1. Cartesian Coordinates – Common Origin; Arbitrary Orientation. 5-1
Before any translation from the Y to the Z system can occur, the respective axes of the two
systems must be parallel, which can be accomplished by two rotations of the Y system. The
first rotation is through angle β about the Y1 axis, resulting in the rotation matrix
Another rotation through angle 6 about the new Y3 axis formed by the 8 rotation
gives
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Point P, now in a system parallel with the Z system, can be translated through the coordinates
of Point A to give
where
Expansion of Equation 5-5 produces the Z coordinates of P
5.10 DERIVATION OF REFERENCE ANGLE RELATIONSHIP IN STRAIGHT
ROPE
The choice of coordinates for the straight-rope analysis requires that a reference-angle
relationship be derived. The derivation presented here results in (0, 6) relationships for both
the constant-angle and uniform motion assumptions. In the body of the report it was stated
that the angle relationship can be determined by noting that the tangents to the helix curve,
formed by the strand, and the double-helix curve, formed by the wire, have the angle, e,
between them.
The tangent to the helix curve is, by Equation 5-6,
And has magnitude
The tangent to the double-helix curve is found by differentiating Equation 5-5
and has magnitude
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The scalar dot product of the two tangents is expressed as
Substituting Equation 5-1 through 5-4 into Equation 5-5 and rearranging gives
Squaring Equation 5-6 and rearranging yields the differential equation,
For a real Lang-lay wire rope, only the positive sign on the right side of Equation 5-7 has
meaning. In all cases, 0 and e increase in magnitude simultaneously.
5.11 RADIUS OF CURVATURE EQUATIONSSTRAIGHT ROPE ANALYSIS
The radius of curvature, p, may be expressed as
In the analysis of the reference angle relationship was derived and-expressed in Equation
5-3. It is a simple, though tedious,task to obtain Z" by differentiating again with respect to θ
Equation 5-15) may be expressed rather simply on a computer program due to the number of
repetitive terms.
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6
CHAPTER SIX
6.1
THE PROCESS OF WIRE ROPE DESIGN FOR A MANUAL WINCH
6.1.1 MATERIAL RANKING INDICES
In ranking of candidate materials for the manual winch, the following factors were
considered: availability, material cost and manufacturing cost.
Availability Index
Availability of a material plays an important role in the selection process. In obtaining the
availability index we considered such factors as availability of material in desired quantity
and time frame, and the form in which the material is supplied.
For the purposes of the selection process, indices of 5, 3 and 1 were allocated for the locally
available materials, not readily available materials and locally unavailable materials
respectively.
Material Cost Index
The prices of materials were obtained from local suppliers1 and are tabulated in database
excel worksheet. Since low cost of a material is desirable, the cost index was obtained as
follows:
=
HSLA Steel was the least expensive material at Kshs 290 and thus it had a cost index of 1.
Example, for UNS S40500 (405 Stainless steel) the cost index is:
=
1
= 0.39189
East African Foundries Ltd, Kensmetal Ltd and other local suppliers in Industrial Area, Nairobi.
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Manufacturing Index
Manufacturing index was obtained on basis of hardness. A material with low Brinell hardness
number (BHN) is easier to machine than one with a high BHN. An average BHN of 60 for
Electrolytic tough pitch (ETP) Copper was chosen and given an index of 1, being considered
to have the best machinability. The other materials were then ranked on this basis.
=
Example, for UNS S40500 (405 Stainless steel) the manufacturing index is:
=
= .
Thus the material that can be machined easily will have a higher manufacturing index.
Composite index
The Composite index was obtained by multiplying the availability index by a weight of 0.55,
the cost index by weight of 0.35 and manufacturing index by 0.1. Thereafter, summing was
done for the weighted indices of availability, cost of material and manufacturing cost for
individual materials.
Example, for UNS 40500 (405 Stainless steel) the composite index is:
= .
∗
+ .
∗ .
+ . ∗ .
= .
Since the idea in all the indices was to maximize the individual index ranking number, the
material with the highest composite index would then be preferred. To achieve this, all the
candidate materials were ranked on the basis of the composite index and then sorted to get the
top fifteen candidate materials. The material with the highest compound index was selected
as the best candidate for the production of the wire rope based on the chosen materials’
selection criteria. The list of the top fifteen candidate materials based on their composite
index is shown in the appendix.
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6.2
SUPPORT INFORMATION
Support Information gives a detailed profile of each candidate material. The data
requirements for support information differ greatly from those for the screening or ranking
step. Typically, it is the non-quantifiable information which is sought. An example of Support
Information is2:
UNS K02002A515-55 Steel:

Material Composition: Iron 98%, Carbon 0.2%, Manganese 1.03%, Phosphorous
0.04%, Sulphur 0.05%, Silicon 0.28%, Copper 0.20%.

Maximum plate thickness is 63.4mm.

Much stronger and tougher than ordinary carbon steels.

Ductile with elongation at failure equal to 22% for a 50mm specimen.

Characterized by good corrosion resistance and high hardness.

Machinability is characterized by long, gummy chips. It can be machined in the
annealed condition.

It’s welded by common fusion and resistance methods, but should not be joined by
oxyacetylene welding.

6.3
Available in many forms e.g. plate, round bar, forgings, tubings.
MATERIALS SELECTION PROCESS
The material selection system consists of a MATLAB application with a database that is
based on Microsoft Excel i.e. a *.xlsx database. This database stores all the information that
can be used to calculate the appropriate wire rope. The database is accessed by the MATLAB
application and the appropriate information is retrieved for manipulation.
Table
1.Materials Properties
2
Field
Type
Description
string
Unique identifier
material.
UNS No
string
Holds value of UNS number
Material Name
string
Holds material name
Id
of
the
Adopted from www.matweb.com
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Form
string
Holds material form
Yield Strength
string
Holds value of yield strength of
the material
Tensile Strength
string
Holds value of tensile strength
of the material
Density
string
Holds value of density of the
material
Elastic Modulus
string
Holds value of elastic modulus
of the material
Hardness
string
Holds value of hardness of the
material
Availability Index
string
Holds value of availability
index of the material
Cost Index
string
Holds value of cost index of the
material
Manufacturing
Index
string
Holds
value
of
the
manufacturing index of the
material
Composite Index
string
Holds the value of composite
index value of the material
Below is the image of the database as it appears on the excel spread sheet
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6.3.1 THE WIRE ROPE MATERIAL SELECTION PROCESS
To run the system, double click on DTProgram.m file in the folder given, when the
MATLAB
Program open with the appropriate code showing press the F5 button or, alternatively, click
the run button which looks like this
. A screen appears and this is the home screen which
is divided into 3 categories and the user fills in the appropriate values into the corresponding
textboxes from the Safety factor to the design variables for a wire rope.
On clicking the select wire rope materials button a function is called to check whether all the
input boxes have been filled, if not, the user is prompted to fill in the blank input box.
However, if all the input boxes have been appropriate imputed the program calls a function
that calculates, first the needed parameters using the formulas given in chapter five from
input values then uses this values to rank the materials in order of appropriateness.
The program uses these processes to rank and select a material. First the program screens the
materials using go/no-go parameters and eliminates those materials that do not meet the
requirements, for instance in this case the program eliminates all the materials whose shapes
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does not conform with the patterns of a wire rope(i.e. materials which are provided by the
manufacturer in the form of a plate are eliminated). Secondly the allowable stress is then
calculated from the shear strength of the materials of the materials that have passed the
screening and a corresponding diameter calculated. A table is then generated with the
materials UNS Number, Name, Shear Strength, diameter and composite score. The materials
in the table are then arranged in order of decreasing composite score and the top 3 materials
presented to the user in the format of the table. This process is used for all wire ropes’
materials
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7
DISCUSSION
The selection of a material for machine part or structural member is one of the most
important decisions the engineering designer has to make. Poor material choice can lead to
failure of a part or system or to unnecessary cost. The process of materials selection is
difficult one and typically involves multiple conflicting material characteristics, a very large
number of materials as well as large number of constraints.
A good material selection process considers the limiting factors for a particular design
exercise which can be divided into functional requirements, manufacturing process, cost
considerations and operating parameters. The selection of candidate materials for the wire
rope was done in two stages; screening of the large material database and ranking of qualified
materials.
In the first step, using availability as the non- discriminating parameter all locally
unavailable materials were eliminated from further consideration in the selection. The second
step used go/no-go parameters as the basis for screening. In this case, the materials’ shape
was considered as the go/no-go parameter. Therefore, for any material to qualify it had to
meet this condition.
After screening, the second stage involved calculating the wire rope diameters with the
properties of the qualified materials and then ranking the qualified materials using composite
index. The composite index for a given material, by using the Analytic hierarchy process
(AHP), was obtained by multiplying the availability index by a weight of 0.55, the cost index
by a weight of 0.35, and the manufacturing index by a weight of 0.1 and thereafter summing
the weighted indices3. The material with the highest composite index was ranked the best by
the material selection system.
Different materials scored differently in the different indices (i.e. availability, cost and
manufacturing). No particular material was exclusively favored by all factors. Some scored
high on some indices and poorly on others while others were just fair. For example, Low
Carbon Steels and Low alloy Steels scored highly in the availability index as well as cost
3
Weighted index= weight *index.
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index. On the other hand, Aluminium alloys scored well in the availability index but poorly
in the cost index.
From the list of the three qualified materials, UNS K11576 HSLA Steel was ranked the
highest with a composite index of 3.1387. Considering the first three materials the decision
on which material to use relied on supporting information. The supporting information for the
two materials is given below:
UNS K11576 High Strength Low Alloy Steel

Material Composition: Fe 95-97%, C (0.1-0.2%), Mn (0.6-1%), P (0.035%), S
(0.04%), Si (0.15-0.35%), Cr (0.4-0.65%), Ni (0.7-1%), Mo (0.4-0.6%), V (0.030.08%), Cu (0.15-0.5%), B (0.002-0.006%).

Maximum plate thickness is 64 mm.

Ductile with elongation at failure equal to 18% for a 50mm specimen.

Much stronger and tougher than ordinary carbon steels.

Highly resistant to corrosion.

Available in many forms e.g. bar, plate, tube.
From the supporting information, the three materials had almost similar attributes, and thus
UNS K11576 HSLA Steel was chosen as the best material for the wire rope material because
of its higher composite index.
This automated material selection system helps the designer perform the rigorous process of
material selection for the wire rope material by giving accurate information at fast speeds
thus saving time and money during design. However, several challenges were encountered
during the development of this selection system. Among them were lack of easy access to
comprehensive and accurate information on the availability of the different materials and
their local cost.
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8
CONCLUSION
The objectives of the project were met as a computer program for materials selection of for a
wire rope (for a manual winch) was done and implemented on a digital computer using
MATLAB as the programming language.
From the project results we discovered the optimal selection of engineering materials is done
in two stages: screening followed by ranking. The first stage reduces the large material
database to a small candidate list which meets the critical property limits as defined by the
design equations. The second stage involves ranking the candidate materials using composite
index. Supporting information is then sought and used to narrow down the ranked materials
to a final choice allowing a definite match to be made between design requirements and
material attributes.
The selection of a suitable wire rope material for a manual winch was successfully
implemented as an information processing routine on a computer system. Only data input was
required, the application developed did the data manipulation and output a list of suitable
materials ranked in order of preference. The selection of UNS K11576 HSLA Steel was
therefore not based on past experience but on stepwise selection from first principles.
101
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9
RECOMMENDATIONS
1. Documentation of precise and accurate information on the materials available in the
Kenyan market and their costs
2. Future students to work on integrating all the previous projects dealing with selection of
various entities of a manual winch into one congruent program.
3. Future students to approach local wire rope manufacture companies to test the workability
of the wire rope selection program.
4. Future students to extend this program to select materials for numerous engineering
systems.
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10 REFERENCES & APPENDICES
1. MADARA OGOT and GÜL KREMER, Engineering Design. A Practical Guide,
Trafford Publishing Co., Inc., 2004.
2. TAHA, A. H, Operations Research. An introduction, 8th Edition. Prentice Hall of
India Private Ltd, 2008.
3. WILLIAM D. CALLISTER, DAVID G. RETHWISCH, Materials Science and
Engineering: An Introduction, 7 th Edition, John Wiley and Sons, 2007.
4. RICHARD G. BUDYNAS AND J. KEITH NISBETT, Shigley’s Mechanical
Engineering Design, 8th edition, McGraw Hill, 2008.
5. SHIGLEY, J E, MISCHKE, C R, Mechanical Engineering Design, 6E, 2001,
McGraw Hill.
6. ODOURI, M.F, MHCL Notes on wire rope design and selection.
7. MOGAKA DAVIDSON & MOMANYI GODFREY, Development of a Materials
Selection Process in Engineering Design and Manufacturing, BSc Mechanical
engineering, University of Nairobi 2012
8. Materials Selection, www.newagepublishers.com/samplechapter/000901.pdf
9. Modes of failure www63.homepage.villanova.edu/michael.raulli/.../
modes_of_failure.pdf
10. Material selection Process www.ipcc.ch/pdf/assessment-report/ar4/wg3/ar4-wg3chapter9.pdf
11. Material Selection www.cae.wisc.edu/~me349/lecture_notes/material_selection.pdf
12. VERMEULEN EUROPOORT, Standard Wire Ropes, Moezelweg
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11 APPENDICES
11.1 Tables
UNS
Number
Material
Name
K11576
HSLA Steel
A285-C
Steel
A515-70
Steel
A516-60
Steel
A516-60
Steel
A515-55
Steel
AL516-65
Steel
A515-60
Steel
A516-55
Steel
A516-70
Steel
405 Stainless
Steel
410 Stainless
Steel
409 Stainless
Steel
446 Stainless
Steel
403 Stainless
Steel
436 Stainless
Steel
302 Stainless
Steel
442 Stainless
Steel
347 Stainless
Steel
321 Stainless
Steel
317LM
K02801
K01800
K02100
K02401
K02002
K02403
K02800
K01800
K02700
S40,500
S41,000
S40,900
S44,600
S40,300
S43,600
S30,200
S44,200
S34,700
S32,100
S31,725
Yield
Tensile
Strength Strength
Density
Elastic
Modulus Hardness Contact
(BHN)
stress (MPa)
(GPa)
193
155
1.2053
(MPa)
690
(MPa)
795
(Kg/m3)
7850
205
380
7850
200
108
0.10267
260
485
7850
200
109
0.16515
220
415
7850
200
122
0.11824
220
414
7850
200
124
0.11824
415
550
7850
200
118
0.42075
240
450
7850
200
133
0.14072
240
450
7850
200
133
0.14072
205
380
7850
200
122
0.10267
290
485
7850
200
145
0.20546
205
415
7870
170
124
0.12078
405
415
7870
180
124
0.44524
240
450
7800
200
131
0.14072
275
485
7870
200
144
0.18475
205
485
7870
190
144
0.10807
365
530
7870
190
147
0.3426
205
515
7860
193
155
0.10639
275
515
7870
190
155
0.19448
205
515
8030
190
155
0.10807
205
515
8030
190
155
0.10807
205
515
8030
198
155
0.1037
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S31,635
S43,400
S30,500
S31,726
S34,800
S21,000
S20,910
C89520
C89510
C61300
C60800
C61300
A95154
C11000
C10200
C89320
C12200
A96061
C14200
A95086
A95083
A96063
C61400
A92024
Stainless
Steel
316Ti
Stainless
Steel
434 Stainless
Steel
305 Stainless
Steel
317L4
Stainless
Steel
348 Stainless
Steel
201 Stainless
Steel
22-13-5
Stainless
Steel
EnviroBrass2
EnviroBrass1
Aluminium
Bronze 7%
Aluminium
Bronze 6%
Aluminium
Bronze 7%
Aluminium
5154
ETP Copper
Oxygen free
Copper
DHP Copper
AL6061
DPA Copper
Aluminium
5086
Aluminium
5083
Aluminium
6063
Aluminium
Bronze D
Aluminium
2024
205
515
7860
193
155
0.10639
365
530
7800
200
157
0.32547
240
585
8000
193
155
0.14582
240
550
8030
198
163
0.14214
240
620
8000
195
160
0.14432
260
655
8000
200
195
0.16515
380
690
8030
200
203
0.35277
121
119
176
185
7890
7890
115
115
68
66
0.06221
0.06017
240
540
7890
115
98
0.24472
130
345
8170
121
80
0.06824
193
447
7890
115
91
0.15826
75
205
2660
70
58
0.03926
105
250
8890
120
60
0.04489
180
205
8940
115
62
0.13766
125
205
145
205
241
250
241
250
7890
8940
2700
8910
115
117
69
115
65
65
65
67
0.06639
0.1755
0.14888
0.17855
117
262
2660
71
70
0.0942
110
270
2660
71
77
0.08327
195
225
2700
69
82
0.26926
205
485
7890
115
95
0.17855
290
440
2780
73
120
0.56289
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A92014
A97075
Aluminium
2014
Aluminium
7075
414
483
1800
73
135
1.14718
455
530
2810
72
150
1.40489
Form
Cost per kg
Availability
Index
Cost Index
Manufacturing
Index
Composite
Index
Bar
Plate
Plate
Bar
Bar
Bar
Plate
Plate
Plate
Bar
Tube
Tube
Plate
Tube
Plate
Sheet
Plate
Plate
Bar
Bar
Bar
Plate
Plate
Plate
Bar
Plate
Plate
Bar
Casting
Casting
290
380
400
380
380
400
400
400
440
400
740
740
920
930
930
980
920
940
940
940
940
940
980
1020
1000
1035
1090
1150
1035
1150
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
3
1
0.763157895
0.725
0.763157895
0.763157895
0.725
0.725
0.725
0.659090909
0.725
0.391891892
0.391891892
0.315217391
0.311827957
0.311827957
0.295918367
0.315217391
0.308510638
0.308510638
0.308510638
0.308510638
0.308510638
0.295918367
0.284313725
0.29
0.280193237
0.266055046
0.252173913
0.280193237
0.252173913
0.387096774
0.555555556
0.550458716
0.491803279
0.483870968
0.508474576
0.45112782
0.45112782
0.491803279
0.413793103
0.483870968
0.483870968
0.458015267
0.416666667
0.416666667
0.408163265
0.387096774
0.387096774
0.387096774
0.387096774
0.387096774
0.387096774
0.382165605
0.387096774
0.36809816
0.375
0.307692308
0.295566502
0.882352941
0.909090909
3.138709677
3.072660819
3.058795872
3.066285591
3.06549236
3.054597458
3.048862782
3.048862782
3.029862146
3.04512931
2.935549259
2.935549259
2.906127614
2.900806452
2.900806452
2.894387755
2.899035764
2.896688401
2.896688401
2.896688401
2.896688401
2.896688401
2.891787989
2.888219481
2.888309816
2.885567633
2.873888497
2.86781752
2.936302927
1.82916996
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Sheet
Tube
Tube
Tube
Sheet
Sheet
Casting
Tube
Tube
Tube
Tube
Tube
Tube
Sheet
Tube
Tube
Tube
1780
1670
1700
2010
2010
2025
1610
2010
2070
2010
2130
2130
2050
1700
2010
2025
2540
3
3
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0.162921348
0.173652695
0.170588235
0.144278607
0.144278607
0.143209877
0.180124224
0.144278607
0.140096618
0.144278607
0.136150235
0.136150235
0.141463415
0.170588235
0.144278607
0.143209877
0.114173228
0.612244898
0.75
0.659340659
1.034482759
1
0.967741935
0.923076923
0.923076923
0.923076923
0.895522388
0.857142857
0.779220779
0.731707317
0.631578947
0.5
0.444444444
0.4
1.768246962
1.785778443
1.775639948
0.703945788
0.700497512
0.69689765
0.705351171
0.692805205
0.691341509
0.690049751
0.683366868
0.67557466
0.672682927
0.672863777
0.650497512
0.644567901
0.62996063
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11.2 Drawings
An oblique view of the manual winch with a wire rope
A side view of the manual winch
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Application of a Manual Winch with a Wire Rope
AutoCAD Design Drawing of a Manual Winch Using a Wire Rope
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12 THE CODE
WIRE MATERIAL SELECTION CODE
function varargout = DTProgram(varargin)
% DTPROGRAM MATLAB code for DTProgram.fig
%
DTPROGRAM, by itself, creates a new DTPROGRAM or raises the existing
%
singleton*.
%
%
H = DTPROGRAM returns the handle to a new DTPROGRAM or the handle to
%
the existing singleton*.
%
%
DTPROGRAM('CALLBACK',hObject,eventData,handles,...) calls the local
%
function named CALLBACK in DTPROGRAM.M with the given input arguments.
%
%
DTPROGRAM('Property','Value',...) creates a new DTPROGRAM or raises the
%
existing singleton*. Starting from the left, property value pairs are
%
applied to the GUI before DTProgram_OpeningFcn gets called. An
%
unrecognized property name or invalid value makes property application
%
stop. All inputs are passed to DTProgram_OpeningFcn via varargin.
%
%
*See GUI Options on GUIDE's Tools menu. Choose "GUI allows only one
%
instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES
% Edit the above text to modify the response to help DTProgram
% Last Modified by GUIDE v2.5 28-Apr-2013 17:13:24
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',
mfilename, ...
'gui_Singleton', gui_Singleton, ...
'gui_OpeningFcn', @DTProgram_OpeningFcn, ...
'gui_OutputFcn', @DTProgram_OutputFcn, ...
'gui_LayoutFcn', [] , ...
'gui_Callback', []);
if nargin && ischar(varargin{1})
gui_State.gui_Callback = str2func(varargin{1});
end
if nargout
[varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT
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% --- Executes just before DTProgram is made visible.
function DTProgram_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% varargin command line arguments to DTProgram (see VARARGIN)
% Choose default command line output for DTProgram
handles.output = hObject;
% Update handles structure
guidata(hObject, handles);
% UIWAIT makes DTProgram wait for user response (see UIRESUME)
% uiwait(handles.DTProgram);
% --- Outputs from this function are returned to the command line.
function varargout = DTProgram_OutputFcn(hObject, eventdata, handles)
% varargout cell array for returning output args (see VARARGOUT);
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Get default command line output from handles structure
varargout{1} = handles.output;
function etSf_Callback(hObject, eventdata, handles)
% hObject handle to etSf (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etSf as text
%
str2double(get(hObject,'String')) returns contents of etSf as a double
% --- Executes during object creation, after setting all properties.
function etSf_CreateFcn(hObject, eventdata, handles)
% hObject handle to etSf (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
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if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function etWirerope2Dia_Callback(hObject, eventdata, handles)
% hObject handle to etWirerope2Dia (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etWirerope2Dia as text
%
str2double(get(hObject,'String')) returns contents of etWirerope2Dia as a double
% --- Executes during object creation, after setting all properties.
function etWirerope2Dia_CreateFcn(hObject, eventdata, handles)
% hObject handle to etWirerope2Dia (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function etWirerope3Dia_Callback(hObject, eventdata, handles)
% hObject handle to etWirerope3Dia (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etWirerope3Dia as text
%
str2double(get(hObject,'String')) returns contents of etWirerope3Dia as a double
% --- Executes during object creation, after setting all properties.
function etWirerope3Dia_CreateFcn(hObject, eventdata, handles)
% hObject handle to etWirerope3Dia (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
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if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function etls2_Callback(hObject, eventdata, handles)
% hObject handle to etls2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etls2 as text
%
str2double(get(hObject,'String')) returns contents of etls2 as a double
% --- Executes during object creation, after setting all properties.
function etls2_CreateFcn(hObject, eventdata, handles)
% hObject handle to etls2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function eta2_Callback(hObject, eventdata, handles)
% hObject handle to eta2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of eta2 as text
%
str2double(get(hObject,'String')) returns contents of eta2 as a double
% --- Executes during object creation, after setting all properties.
function eta2_CreateFcn(hObject, eventdata, handles)
% hObject handle to eta2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
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if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function etc2_Callback(hObject, eventdata, handles)
% hObject handle to etc2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etc2 as text
%
str2double(get(hObject,'String')) returns contents of etc2 as a double
% --- Executes during object creation, after setting all properties.
function etc2_CreateFcn(hObject, eventdata, handles)
% hObject handle to etc2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function etbeta_Callback(hObject, eventdata, handles)
% hObject handle to etbeta (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etbeta as text
%
str2double(get(hObject,'String')) returns contents of etbeta as a double
% --- Executes during object creation, after setting all properties.
function etbeta_CreateFcn(hObject, eventdata, handles)
% hObject handle to etbeta (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
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if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function etLoadApplied_Callback(hObject, eventdata, handles)
% hObject handle to etLoadApplied (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etLoadApplied as text
%
str2double(get(hObject,'String')) returns contents of etLoadApplied as a double
% --- Executes during object creation, after setting all properties.
function etLoadApplied_CreateFcn(hObject, eventdata, handles)
% hObject handle to etLoadApplied (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function etWirerope1Length_Callback(hObject, eventdata, handles)
% hObject handle to etWirerope1Length (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etWirerope1Length as text
%
str2double(get(hObject,'String')) returns contents of etWirerope1Length as a double
% --- Executes during object creation, after setting all properties.
function etWirerope1Length_CreateFcn(hObject, eventdata, handles)
% hObject handle to etWirerope1Length (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
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end
function etB1_Callback(hObject, eventdata, handles)
% hObject handle to etB1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etB1 as text
%
str2double(get(hObject,'String')) returns contents of etB1 as a double
% --- Executes during object creation, after setting all properties.
function etB1_CreateFcn(hObject, eventdata, handles)
% hObject handle to etB1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
function etPressureAngle_Callback(hObject, eventdata, handles)
% hObject handle to etPressureAngle (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etPressureAngle as text
%
str2double(get(hObject,'String')) returns contents of etPressureAngle as a double
% --- Executes during object creation, after setting all properties.
function etPressureAngle_CreateFcn(hObject, eventdata, handles)
% hObject handle to etPressureAngle (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
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function etWirerope1Dia_Callback(hObject, eventdata, handles)
% hObject handle to etWirerope1Dia (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of etWirerope1Dia as text
%
str2double(get(hObject,'String')) returns contents of etWirerope1Dia as a double
% --- Executes during object creation, after setting all properties.
function etWirerope1Dia_CreateFcn(hObject, eventdata, handles)
% hObject handle to etWirerope1Dia (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
%
See ISPC and COMPUTER.
if ispc && isequal(get(hObject,'BackgroundColor'),
get(0,'defaultUicontrolBackgroundColor'))
set(hObject,'BackgroundColor','white');
end
% --- Executes on button press in pbCalculateWirerope.
function pbCalculateWirerope_Callback(hObject, eventdata, handles)
% hObject handle to pbCalculateWirerope (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
%to get the values of the variables from the input boxes
if ~isempty(get(handles.etLoadApplied,'string'))
F = str2num(get(handles.etLoadApplied,'string'));
else
msgbox('Please Enter a Value for applied Force','VALUE MISSING')
return
end
if ~isempty(get(handles.etWirerope1Length,'string'))
ls1 = str2num(get(handles.etWirerope1Length,'string'));
else
msgbox('Please Enter a Value for Input Wirerope Length','VALUE MISSING')
return
end
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if ~isempty(get(handles.etB1,'string'))
b1 = str2num(get(handles.etB1,'string'));
else
msgbox('Please Enter a Value for B1 ','VALUE MISSING')
return
end
if ~isempty(get(handles.etPressureAngle,'string'))
phi = str2num(get(handles.etPressureAngle,'string'));
else
msgbox('Please Enter a Value for the Pressure Angle ','VALUE MISSING')
return
end
if ~isempty(get(handles.etWirerope1Dia,'string'))
D1 = str2num(get(handles.etWirerope1Dia,'string'));
else
msgbox('Please Enter a Value for the Diameter of Wire rope 1','VALUE MISSING')
return
end
if ~isempty(get(handles.etSf,'string'))
sf = str2num(get(handles.etSf,'string'));
else
msgbox('Please Enter a Value for the Saftey Factor ','VALUE MISSING')
return
end
%to calculate Torque
T = F * L;
%to calculate tangential forces in Wirerope 1
F1t = ((2*T)/D1);
%to calcute radial forces in Wirerope 1. the pressure angle must first be
%converted to radian for correct calculation.
F1r = F1t * tan ((phi/180)*pi);
%to determine the reaction
R1 = F;
%to determine the max moment
M1 = F * b1;
% to get values from the database
[num,text,raw] = xlsread('database.xlsx','sheet1');
matSSt = [raw];
matSSn = [num];
[m,n] = size(matSSt);
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%for k = 3:(m-1)
% if matSS(k,9) == 'Bar'
% tao = ((str2num(matSS(k,4)))/sf) * (10^6)
%tao = str2num(matSS(k,4))
% end
%end
r = 1;
for k = 3:(m-1)
v = strcmpi(matSSt(k,9), 'Bar');
if v == 1
tao = (matSSn(k,4)/sf) * (10^6);
ds1 =(((sqrt(M1^2 + T^2)) * (16 / (pi * tao)))^ (1/3));
mattable(r,1) = matSSt(k,1);
mattable(r,2) = matSSt(k,2);
mattable(r,3) = matSSt(k,4);
mattable(r,4) = num2cell(ds1);
mattable(r,5) = matSSt(k,14);
r = r + 1;
end
end
mattable = sortrows(mattable , -5);
l = 4;
for j = l:(r-1)
mattable(l,:) = [];
end
set(handles.tWirerope1Mat,'data',mattable);
%to calculate the diameter and display it appropriatley
%ds1 = (((sqrt(M1^2 + T^2)) * (16 / (pi*tao)))^(1 / 3));
%ds1 =(((sqrt(M1^2 + T^2)) * (16 / (pi * tao)))^ (1/3));
%num2str(ds1);
%(set (handles.stWirerope1Dia,'string',ds1));
%to calculate the values for the Square x section of the Wirerope
%w = ((T / (0.208 * tao))^ (1/3));
%num2str(w);
%(set (handles.stSqValue,'string',w));
end
Wireropedata = getappdata(handles.pbCalculateWireropes,'Wireropedata');
DTBProgram('DTProgramData', handles.DTProgram);
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