MAE486_Fall11_L16_S - MAE 486 Design of Mechanical Systems...

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Unformatted text preview: MAE 486 Design of Mechanical Systems Lecture 16 Fall 2011 Today s topics: Design with Materials (Chapter 12); Modeling (Chapter 10); Announcement Safety seminar: October 31st (Monday). Mandatory for using the machine shop; Mid-term exam: November 2nd (Wednesday) Review: •  •  •  •  •  Design for Corrosion Resistance How serious is the problem? How to avoid/minimize? What causes corrosion? What are the different types of corrosion? What are different approaches to prevent corrosion? –  What is the main cause of corrosion? •  What else approach we could apply? –  SeparaDon: –  Metal part design: •  •  •  •  •  •  What is wear? What causes wear? Science to study wear: Is wear a material property? What does wear depend on? What are the different approaches to prevent wear? Review: •  •  •  •  •  •  Design with PlasDcs Why plasDcs? Polymer vs. metals: What are the differences? How to characterize polymers? What are different classes? TP vs. TS: Which are more common? Further classificaDon of TP? Other ProperDes of PlasDcs •  Do plasDcs corrode? Why? •  How do them react to the environment? •  PlasDc matrix composite materials –  –  –  –  Modulus Strength DucDlity Weight Design for SDffness •  How to increase structure sDffness made of plasDcs? •  Example: Maximum beam deflecDon with end load: Time ­Dependent Part Performance •  How to characterize the mechanical properDes of plasDcs? •  What is the physical meaning? •  What behaviors of plasDcs show that? –  Creep: –  Stress relaxa,on: measures the decreasing stress required to cause a constant strain at a constant temperature, e.g., the loosening of a self ­tapping screw is a result of stress relaxaDon. Design for Time ­Dependent Part Performance •  How to take the Dme ­dependent behavior into account? •  What do we need to determine?  DeformaDon/DeflecDon (Maximum) –  Step 1: –  Step 2: –  Step 3: –  Step 4: stress/strain apparent creep modulus. –  Step 5: Example: Design for Creep of PlasDcs •  Problem Statement: Beam of PET Composite –  Material composiDon: A simple beam of polyethylene terephthalate (PET) reinforced with 30 volume percent of short glass fibers; –  Load condiDon: StaDcally loaded with 10 lb in the middle of the beam. –  Geometry dimension: The beam is 8 in. long, 1 in. thick, –  Physical parameter: I=0.0025 in. –  QuesDon: DeflecDon under load at midspan? –  Which formula to use? –  What are known? What are unknown? How to find the unknown? Example: Design for Creep of Plas,cs •  Bending moment: •  Bending stress at the center of the beam •  Creep strain at 1000 h with 4000 psi at room temperature 73 F (23o). This gives a strain of 0.7%. Example: Design for Creep of Plas,cs (cont’d) Example: Design for Creep of Plas,cs (cont’d) •  The apparent modulus is then •  The deflecDon at midspan is •  If the temperature is raised to 250 F, the deflecDon is then 0.13 in. (Ea=33000 psi) Review for Mid ­Term •  What are the main topics we have discussed? –  –  –  –  –  –  –  Product development process; Problem definiDon; Team management; Concept generaDon; Decision making; Material selecDon; Design with materials; Review for Mid ­Term •  Product development: –  –  –  –  –  –  Different phase of design; CAE & concurrent engineering; Design codes & standards; Design review; Redesign; Social consideraDon; •  Problem definiDon –  –  –  –  –  –  –  Customer inputs; Customer survey; Engineering characterisDcs; Benchmarking; Reverse engineering; Quality funcDon development; House of quality; •  Role of different rooms; •  InterpretaDons of RelaDonship matrix and engineering characterisDcs; –  Product design specificaDons; Review for Mid ­Term •  Project management: –  –  –  –  –  Good team member; Team roles; Team dynamics; Problem solving tools; Cause ­finding tools; •  Pareto principle; –  SoluDon finding and implementaDon tools; –  Time management; –  Planning tools: Ganf chart; –  CriDcal path method; •  Concept generaDon: –  Models of the brain and creaDvity thinking; –  CreaDve thinking process; –  CreaDve thinking methods; •  •  •  •  •  •  •  •  Brainstorming Random impact technique; SynecDcs; Concept map; FuncDonal decomposiDon; Morphological analysis; TRIZ; AxiomaDc method; Review for Mid ­Term •  Decision making: –  Basic ingredients in decision making; –  Different types of decision making models; –  Decision making under no uncertainty, with uncertainty; Maximin rule, maximax rule, and combined; –  Concept of uDlity funcDon;   Diminishing marginal uDlity; –  Determine uDlity funcDon: –  Decision tree; –  EvaluaDon methods; –  Pugh concept selecDon method; –  Measurement scale; –  Weighted decision matrix; –  Hierarchical objecDve tree; –  AnalyDcal hierarchy process; •  Key concept: keep consistency; •  Procedure: Apply to criteria first, then design opDons •  Material selecDon: –  Material selecDon at different stages of design; –  SelecDon process; –  Performance characterisDcs; •  Concept of structure; –  Basic types of materials; –  Basic types of material properDes; –  Mechanical properDes of materials; –  Comparison of mechanical properDes of metal, ceramics, glass, and polymer; –  Ashby charts; –  Material performance indices; •  Construct; •  Use of performance indices in M. selecDon; –  Material selecDon with environmental consideraDon; Review for Mid ­Term •  Design with materials; –  Metal •  Corrosion; •  Wear; –  PlasDcs •  ClassificaDon •  Creep; ...
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This note was uploaded on 02/26/2012 for the course 650 486 taught by Professor Zou during the Fall '11 term at Rutgers.

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