How Things are Designed and How Things Move
Robert Love, Venkat Jayaraman
June 26, 2008
SSTP Seminar – Lecture 3
Overview
• Organizational Details
• Presentation
– Design, CAD, Automobiles, Mechanisms, Dynamics
• Discussion
• Activity
– Brief CAD sketch
– Aircraft Dynamics
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Design
• Carnegie Mellon definition:
– "Design is the process of taking something from its existing state
and moving it to a preferred state"
1. Problem or need is identified, often by a customer with
specifications
2. Solution is designed
– Conceptual Design (brainstorming, trade studies)
– Preliminary Design (testing, initial modeling, performance, cost)
– Detailed Design (more testing, end is final product)
3. Realization of design (production)
4. Implementation to meet need
5. Generally sequential, iterative
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Design in a Nutshell
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Design
• What are some methodologies?
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Bio-Inspired, ergonomic, aesthetic , usability
KISS principle-No Rube Goldberg Machines!
User centered vs. Use-centered
Form vs. Function
Best way to catch a mouse?
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Overview
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Engineering drawing
CAD software
Computer aided machining
Computer aided engineering
How automobiles move
– Engine System
– Manual transmission system
Engineering drawing
• Convey the following information
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Geometry
Dimensions
Tolerances
Material
Finish
Why Use CAD?
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Drawing complex parts by hand not easy
Ease of modifications
Standards
Cost Reduction
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CAD softwares
• Drafting – Autocad, Alibre, Solidedge layout
• Solid Modelling – Pro E, Solidworks, Ideas,
Solidedge, Unigraphics
• Analysis – Ansys, CATIA,Nisa, Nastran
Computer aided manufacturing
• CAM – Programming tool that helps
manufacture physical model using
CAD softwares.
• Implemented by CNC machines
• CAD drawing -> G-Code ->
Computer controlled manufacturing
processes such as turning and
drilling
Computer Aided Engineering (CAE)
• Use of information technology in tasks such as analysis,
simulation and design
• CAE areas covers
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Stress analysis on components - FEA (Finite element analysis)
Thermal and fluid flow analysis -CFD (Computational fluid dynamics)
Mechanical event simulation
Optimization
• Phases of CAE
– Pre-processing – defining the model and environmental factors to be applied
to it
– Analysis solver – High performance computers
– Post processing – Visualization of results
Engine system
• Engine system – Converts gasoline into motion
• Four major strokes – Intake, Compression, Power and
exhaust
Main parts of engine are
Piston
Crankshaft
Connecting rod
Valves
Ports
Sump
Spark plug
Increasing Engine Power
• Increasing stroke displacement
• Increasing compression ratio
• Cramming more air fuel mixture into
each cylinder
• Cooling the incoming air
• Allowing intake and exhaust mixture
to flow more easily
• Lighter parts
Manual transmission
• Transmits the motion from the engine to the
wheels
Mechanisms
• Def: Some combination of parts
and linkages to perform a function
• Types of Mechanisms
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Linear Motion
Rotary Motion
Intermittent Motion
Reciprocating Motion
Oscillating Motion
Irregular Motion
• Examples
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Analyzing Things
• Statics
– Description of behaviors without
movement
• Dynamics
– Kinematics: study of motion without
respect to the forces applied
– Kinetics: study of motion under the
influence of forces
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Simplified Models
• Important Concepts:
– Inertial Reference Frame vs. Body
Fixed Reference Frame
– Right vs. Left Handed Coordinate
System
– Scalars, Vectors and Matrices,
Coordinate Transformations,
Transport Theorem
– Identify Degrees of Freedom
– Dealing with Forces: Newton’s Laws
– Tip: Look for symmetry!
– Tip: Note assumptions!
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Flight Dynamics
How many degrees of freedom does an aircraft have?
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References
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http://www.victorpest.com/mouse_instructions.htm
http://www.blendernation.com/wp-content/uploads/2007/01/mousetrap_30.jpg
http://www.aiaadbf.org/
http://en.wikipedia.org/wiki/Mechanism_(technology)
http://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/
thumb/5/5d/Atlas_V_551_with_New_Horizons_on_Lauch_Pad_41.jpg/396pxAtlas_V_551_with_New_Horizons_on_Lauch_Pad_41.jpg&imgrefurl=http://commons.wikim
edia.org/wiki/Image:Atlas_V_551_with_New_Horizons_on_Lauch_Pad_41.jpg&h=599&w=39
6&sz=65&hl=en&start=2&um=1&tbnid=NMIKHOs41g_KM:&tbnh=135&tbnw=89&prev=/images%3Fq%3Datlas%2BV%26um%3D1%26hl%3D
en%26safe%3Dactive%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN
http://www.flying-pig.co.uk/mechanisms/index.html
http://ocw.mit.edu/OcwWeb/Mechanical-Engineering/index.htm
http://www.grc.nasa.gov/WWW/K-12/airplane/rotations.html
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