how things are designed and how things move robert love, venkat jayaraman june 26, 2008 sstp seminar...
TRANSCRIPT
How Things are Designed and How Things Move
Robert Love, Venkat Jayaraman
June 26, 2008SSTP 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 need5. Generally sequential, iterative
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Design in a Nutshell
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Design
• What are some methodologies?– 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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• Engineering drawing• CAD software• Computer aided machining• Computer aided engineering• How automobiles move
– Engine System– Manual transmission system
Overview
• Convey the following information– Geometry– Dimensions – Tolerances– Material – Finish
Engineering drawing
Why Use CAD?
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• Drawing complex parts by hand not easy• Ease of modifications• Standards • Cost Reduction
• Drafting – Autocad, Alibre, Solidedge layout• Solid Modelling – Pro E, Solidworks, Ideas,
Solidedge, Unigraphics• Analysis – Ansys, CATIA,Nisa, Nastran
CAD softwares
• 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 manufacturing
• Use of information technology in tasks such as analysis, simulation and design
• CAE areas covers– 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
Computer Aided Engineering (CAE)
• Engine system – Converts gasoline into motion• Four major strokes – Intake, Compression, Power and
exhaust
Engine system
Main parts of engine are
Piston
Crankshaft
Connecting rod
Valves
Ports
Sump
Spark plug
• 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
Increasing Engine Power
• Transmits the motion from the engine to the wheels
Manual transmission
Mechanisms
• Def: Some combination of parts and linkages to perform a function
• Types of Mechanisms– 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
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How many degrees of freedom does an aircraft have?
References• 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/396px-Atlas_V_551_with_New_Horizons_on_Lauch_Pad_41.jpg&imgrefurl=http://commons.wikimedia.org/wiki/Image:Atlas_V_551_with_New_Horizons_on_Lauch_Pad_41.jpg&h=599&w=396&sz=65&hl=en&start=2&um=1&tbnid=NMIKH-Os41g_KM:&tbnh=135&tbnw=89&prev=/images%3Fq%3Datlas%2BV%26um%3D1%26hl%3Den%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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