Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 2 (13)
ISSN 1843-6188
STUDY ON ENERGY CONSUMPTION IN MACHINABILITY
PROCESSES OF SOME REFRACTORY MATERIALS
Paul Ciprian PATIC, Lucia PASCALE, Luminiţa DUŢĂ, Ryad ZEMOURI
Automation and Computer Science Department, Valahia University of Targoviste, 130082, Romania,
Laboratoire d’Automatique du CNAM, 2 Rue Conté, 75003 Paris, France
E-mail: [email protected]
of cutting process, the material, which ensuring the
minimum cost between n materials, will be considered
the most processed.
Moreover, the material which causes high tool wear,
have a big consumption of tools and, therefore, higher
costs of processing.
In other words, the material will have a lower
machinability. Also, the material who develops high
cutting forces, leads to high energy consumption and,
therefore, high cost of processing and, in this point of
view, the material is considered as having a lower
machinability (Since Patic 6, 7).
Abstract: In the present study one tried, from the general
problem of machinability applied on high alloyed materials, to
highlight a series of studies on energy consumption that occur
during various operations having in view the machinability of
that kind of steels. The problem is even more difficult as the
specialist is tempted to define machinability by cutting tools,
primarily, about his own field of activity. Thus, energy worker
will perform the machinability of a material in specific terms,
having in view the energy consumption, according with cutting
process. The machinability cost indicator is the most complete
one, because, indirectly, take account of other indicators for
assessing of the machinability processes. High cutting forces
means intensive power and energy, that is, high cost of
processing. In addition, it can say that the material which
develops high cutting forces, leads to high energy consumption
and therefore high costs of processing and, from this point of
view, the material is considered as having a lower machinability.
2. STUDY METHODS BASED ON CUTTING
ENERGY CONSUMPTION
The energy used in cutting process of a material can be
considered an important indicator in assessing its
workability. Taking into account the consumption of
cutting tools can be seen that this method is
recommended in all cases (since Lazarescu [4]).
To evaluate the energy absorbed in cutting materials
processes is used cutting the follow devices: watt-meters,
ampere-meters, dynamometers, calorimeters, pendulum
hammers etc. (Since Oprean [5]).
Keywords: Machinability, refractory materials, cutting
process, energy consumption, roughness, neuronal processing
of information.
1. INTRODUCTION
The term "workability" is defined in the Polytechnic
dictionary as "property of a material to be processed
through mechanical operations, in the semi-finished
products with small defects with a small consumption of
machine work or energy, with a higher speed.
A material is considered to have better machinability where:
1. The tool durability is high;
2. The time for machinability is short;
3. The quality of the obtained surface is better;
4. The mechanical or energetic solicitation is low;
5. The energetic consumption is low;
6. The processing precision is high;
7. The splinters have a convenient form.
It can be concluded that machinability of cutting is a
feature of one material that characterizes the ease of it’s
processed into standard test conditions, which can be
standardize.
May be proposed, as an indicator of overall workability,
the minimum cost of processing, both roughing and
finishing operations, so that in the case of roughing, the
very high productivity leads to higher consumption of
cutting tools and electricity.
Therefore, cutting conditions must be chosen so that the
processing cost is minimized. Under the same conditions
3. METHODS BASED ON STUDY OF
ROUGHNESS SURFACE PROCESSING
In this method the surface roughness is used as an
indicator for assessing the workability of materials, being
recommended in finishes processing. Not used into
roughing or semi-finishing operations.
To assess the workability of this method uses samples of
special construction and lathe tools similar to those used
in splinting finishes, with cutting edge roughness, Ra 
0.006 m (Since Enache [2, 3]). Cutting ability of
cutting tools is a feature through one can express the
measure in which the tool satisfied the technological
requirements imposed on the cutting process. The main
criteria for assessing both the ability of cutting tools and
the workability of the materials are the same:
1. The criteria of the tool wear produced by the material;
2. The criteria of the splinting forces or the criteria of
specific energy consuming during working;
3. The criteria of the roughness’s processed surface;
4. The criteria of obtained precision on processed surface.
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 2 (13)
In connection with the mechanical and energetic solicitation
of technological system, on the cutting steels, a
comprehensive assessment in this regard may be based on the
chart in Figure 1 where it appears that the increase in tensile
strength obtaining an increase in specific energy cutting.
ISSN 1843-6188
4. PROCESSING WITH HIGH ENERGY AND
HIGH-SPEED TRANSMISSION
To realize, in short time, the processing, there is a tendency
to increase the speed cutting leading at the experimentation
of ultrafast speeds (4,50010,000 m / min).
With this method was obtained next: increased
productivity, high precision and low roughness (0.08 
2.5 m), less tool wear with increasing speed. The
minimum wear was obtained at cutting speed of over
10,000 m / min. It was noted that the cutting zone
temperature does not increase continuously with
increasing cutting speed (since Lazarescu [4]).
Effects of cooling-lubricating fluid, used during cutting, are:
1. Decrease of temperature of active tool surfaces;
2. Reduce frictions on split-tool and material-tool contact
surfaces (lubricating surfaces);
3. Reduction of forces and of the energy required during
the plastic deformation and material removal processing;
4. Cleaning splinting from cutting area;
5. Processed piece protection against corrosion.
Use-efficiency of cooling-lubricating fluid is generally
dependent not only by own nature but, also, by the
introducing mode in cutting zone.
The principle of neuronal information processing
paradigm, holds that neural networks can be trained only
through examples brought from outside. In other words,
any learning algorithm is used in multilayer networks
based on output estimation error. This is the so-called
problem of difficult learning (hard learning) and is one of
the most important problems of neural network.
An important step in overcoming this problem did an
American chemist and biologist, named John Hopfield in
1982. He presents neural networks as such of content
addressable memories (associative memories). Through his
work he had two major contributions. First, he developed a
type of analysis of networks using the concept of energy
and he concluded that the network reaches in operation, the
minimum energetic consumption and after that the string
output signals no longer change, so stability is reached.
Secondly, he showed that some learning rules like “delta
rule” can be used to adjust the network settings to create
energy minimum (since Patic [8]).
Hopfield neuron model has the characteristic sizes: Vi output signal (V = 0 if the neuron does not emit, V = 1
otherwise); Tij - share link between i neuron and j neuron
(T = 0 if i neuron is disconnected by j neuron) and Ui - the
threshold value at which the neuron emits. Consequently:
Figure 1 The dependence of tensile strength and specific
energy
In the case of steels, a correlation between the shear
strength and specific energy of cutting is shown in Figure 2.
It appears that, with increasing value of shear resistance,
obtain an increase of specific energy.
Figure 2 The dependence of shear resistance and specific energy
The resilience is the property of materials to withstand the
dynamic stresses imposed by impact. Determination of
resilience is done using a pendulum type devices that can
establish absolute power to break through a shock, set in
knowing conditions, of a specimen of some form (since
Patic [8]). It be established a link regarding the dependence
between resilience and mechanical work (energy) specific
on cutting. From the diagrams in Figure 3 it shows that
increasing the resilience to damage by shock leads to
increased specific mechanical work of cutting.
T V  U ;
V becomes 0 if  TijV j  U i .
Vi becomes1 if
ij
j
i
(1)
i
The energy of one neuron can be computed with:
Ei  Vi  TijV j  U i 
(2)
in which, the brackets quantity is called activation
quantity, noted with Ai. For a neural network state be,
compulsory stable, must none of the nodes be activated
so that be changed the emission conditions. So, if a
neuron emits (V = 1), its activation will be positive for
not to stop broadcasting. Similarly, if the neuron does not
Figure 3 The dependence of resilience and specific energy
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ISSN 1843-6188
Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 2 (13)
emit (V = 0) its activation will be negative, for not
compel him to deliver signs.
Consequently, whenever the neural network changes its
state, it is still on the same energy level or descends to a
lower energy level. When there are not available those
lower levels of energy, the network remains stable in the
last state reached (since Abaza [1]).
From the perspective of energetic analysis is now
becoming clear that, the applying of a learning procedure
such as the “delta rule” is not that a simply way to reduce
the network energy status to a minimum.
Still, the Hopfield model has disadvantages. The most
important is related to "pinch" the neural network in.
The way to escape from false minimum power of the
neural system was found by Geoffrey Hinton, in 1986,
and consist in use of "noise", means applying a degree of
uncertainty on state energy. Intuitively, these, can be
illustrated by representing the network status as a ball on
a wavy surface (Figure 4). If the ball have an internal
property which makes it bounce, then is very likely that it
will spend most time in the deepest valley can reach.
Among these, the first three criteria are essential, and the
last two are a secondary importance; is rarely considered
and only in special situations.
5. VARIABLES, FUNCTIONS AND INDICATORS
FOR THE MANUFACTURING PROCESS
Into a technological system, a particular manufacturing
process is defined by a set of process variables, where is
different correlations between. Independent process variables
are input variables, denoted Xj, j = 1, 2, ... j,... k (i.e. physical and mechanical characteristics and structural
characteristics of the working material, the material itself and
tool geometry features, parameters cutting regime, etc.).
Dependent variables are output variables Yp, p = 1, 2, ... p
(characteristics of the splint, tool wear, specific energy
consumed in cutting process, cutting forces, surface
roughness processed etc.).
Interdependence relationship between process variables
forming process functions: Y = F(X1, X2, X3, ... Xj, ... Xp),
where: Y and Xj, j = 1, 2, 3...k are dependent variables,
respectively are independent having in view the study
process. Naming of process functions is determined by the
machinability criteria of that one define that according to
dependent variables, thus distinguishable features cutting
tool wear, specific energy consumption in cutting
functions, features cutting force, surface roughness
features processed etc. (Since Patic [8]). The technical
characteristics of materials, as will be defined below, must
be as small as possible because the material has a better
workability (a higher index value), (i  S2).
The most important features are: the speed (its intensity)
of tool wear, the specific energy consumption in cutting
processed, the roughness of surface, the average size and
shape of detached splints, the deviations from the
prescribed dimensions and geometrical form.
As a result, the total index and the total percentage of
machinability index of the j material compared with those
5 criteria considered most important (u – the wear; e – the
specific energy, r – the processed surface roughness, p –
the dimensional deviations, c – the average size of the
splint) is determined by the follow relationship:
Figure 4 The network status as a ball on a wavy surface
In general, the study of workability includes questions
regarding the tool wear, the cutting forces, the processed
surface roughness, the specific energy consumed in the
process of cutting, the splint size and shape of detached
and the dynamic stability, resulting that machinability
depends both on the material characteristics and cutting
process parameters (since Patic [9]).
Quantitative expression of workability of a material has not
been yet achieved, researchers finding that machinability is
a difficult concept to define and expressed by physical or
mathematical equations, or it is not possible to define, in
quantitative terms, the workability.
The problem is even more difficult to solve as the
specialist is tempted to define the cutting machinability,
primarily, related to its own domain. Thus, the man who
is responsible with energetic consumption will interpret
the machinability in terms of energy consumption during
the splinting process, a manufacturer of machine tools
will be interested regarding the cutting forces and
possibly regarding the plastic-elastically properties of
used materials and a manufacturer of tools will be
deemed that a material with a good workability produces
low wear of cutting tools (since Patic [8]).
Cutting machinability of a material is defined as a
complex technical characteristics expressed by the extent
to which it meets in a technological environment
functional, technical and economic requirements, impose
during the cutting process (since Patic [9]). The main
criteria for assessing the workability of materials are:
1. Wear criteria produced, on the blade edge, by material;
2. Cutting forces criteria or specific energy criteria
consumed during the splinting process;
3. Roughness criteria applied on processed surface;
4. Precision criteria obtained on processed surface;
5. Splint detached shape criteria during the splinting process.
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(3, 4)
To determine the priority exponent’s s is necessary to
include the additional costs imposed by the need to
fragment the splint (additional costs with special sharpening
tool, with plates of complex shapes for tools, with static or
dynamic fragmentation device of the splint etc.).
Practically, in the case of the consumed specific energy
criteria are a minor importance, the share exponent’s e
may take a low value (i.e. 0.2).
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 2 (13)
not established, yet, a single indicator that expresses the
entire reaction to a material cutting.
The problem is even more difficult as the specialist is
tempted to define the cutting machinability, primarily,
related to its own domain.
Thus, the worker responsible with energy consumption
will perform the workability of a material through
specific energy consumption during the splinting process;
a manufacturer of machine tools will be interested by the
size of the cutting forces and moments; a producer of
components in large series will be interested in
processing time; the tool producer will be deemed that a
material is easily processed, whether that produced low
wears of cutting tools in manufacturing process etc.
As a general conclusion, however, one can estimate that
the cost of processing indicator is the most
comprehensive indicator, because, indirectly, it takes
account of other indicators for assessing the workability.
High cutting forces means high power and high energy
consumption, respectively, high cost of processing.
A high wear at cutting tool means higher consumption
and, therefore, high cost of processing.
6. THE EXPERIMENT - A KEY ISSUE IN
ENGINEERING
Technological systems are composed by natural elements
and its functionality is determined through the ability to
achieve of the specific material transformation, of energy
or information. Causal connections that characterize the
functionality of technological systems are expressed in a
general form by the output equation (response function)
of them (since Patic [8]):
(5)
y = f(x, s)
in which:
1. the x inputs represent actions (commands) exerted on
the system;
2. the y outputs are assigned to the system and are
changed because of input variations.
One notes that equation (6) ignores the manufacturing
regime, the machine tool depreciation cost, or power
consumption etc.
7. RESISTANT STAINLESS STEEL ORDERING
USING THE MINIMUM COST OF
PROCESSING CRITERIA
9. REFERENCES
One chooses four types of special steels (heat resistance
steels) shown below:
[1] Abaza B. – Preliminary research and some
contributions, regarding the applications of the
artificial intelligence systems in composites
manufacturing, Referat no. 2 PhD, Bucharest, 1999.
[2] Enache Şt., Străjescu E., Tănase I., Opran C. –
Determination of Tool Cutting Capacity, Annals of
the CIRP, vol. 41/1, 1992.
[3] Enache Şt. – The quality of the processed surfaces,
Technical Publishing House, Bucharest, 1979.
[4] Lăzărescu I., Abrudan G., Bejan E., Şteţiu G. – The
splinting and splinting tools, Didactical and
pedagogical Publishing House, Bucharest, 1976.
[5] Oprean C., Şteţiu G., Şteţiu M. – The turning of
materials, Sibiu University Publishing House, 1995.
[6] Patic P.C., Vlase A. – Contributions regarding the
experimental determinations of a regression equations
for tool’s wear and splinting speed using turning of
special steels, In « TCMM », nr. 38, Technical
Publishing House, Bucharest, November 8-9 1999.
[7] Patic P.C., Vlase A. – Contributions regarding the
experimental determinations of regression equations
for tool’s wear and splinting speed using in drilling
of special steels, In « TCMM », nr. 38, Technical
Publishing House, Bucharest, November 8-9 1999.
[8] Patic P. C. – Contributions regarding the splinting
process study of heat resistance steels, PhD These,
Politehnica University Bucharest, 2000.
[9] Patic P.C., Zemouri R. - Neural Approaching of
Material’s Processing, The Scientific Bulletin of
Valahia University Materials and Mechanics, ISSN
1844-1076, 2009.
[10] Vlase A., Patic P. C. – Design of the processing
operations on the conventional lathe and numerical
command machines, Economic Publishing House,
Bucharest, 2004.
1. X12CrNiTi 18.9 STEEL;
2. 10H11N23T3MRVD STEEL;
3. 10NiCr180 STEEL;
4. OLC 45 - STANDARD STEEL.
In order to make a sort of four processing steels using
the minimum cost criteria, one follow the minimum cost
relationship given by the specialty literature (since Vlase
[10]):
C
l  Ap

C2 

 C1 1 
n s t
C

T

 (lei)
1
ISSN 1843-6188
(9)
in which: l is the processing lengths, in mm;
Ap – the added processing, in mm;
n – the speed of the piece, during the splinting process, in
rot/min;
s – the advance work, in mm/rot;
t – the splinting depth, in mm;
C1 – the worker salary, in lei/min;
T – the economic durability of splinting tool, in min;
C2 – the expenses of the tool operating, in lei.
8. CONCLUSION
Machinability concept is part of the current terminology of
the researcher’s cutting theory, many trying and succeeding,
more or less to define its characteristics, scope and limits.
Regarding the research methods of machinability using
splinting process one find out that their number is
relatively large and not exist stringent provisions
applying, depending on the material processed.
One can say that so far has not agreed on a widely
accepted definition of cutting machinability, because it
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