DESIGN PHASE What kind of analysis you need to do? MIME Senior Design Projects - Spring 2013

Overview  Design/Analysis Requirements  Common Design Issues  Welds  Fatigue  Safety  Quality

Design Requirements  What type of analyses do I need?

Design Requirements  Measure twice, cut once  Make sure you do adequate calculations and analysis  Tendency to build first, design later Works if you’re right the first time Costs material, effort, and time if you’re wrong  Anticipate use  Anticipate misuse!

Design/Analysis  FREE BODY DIAGRAM  FEA  Approximate Design/Calculations  Is it a beam or a plate?

Design/Analysis - FEA  Quality of input determines quality of output  “Magic” Black Box  Factors  Solid model quality  Correct boundary conditions  Load accuracy  Proper material selection  Mesh quality  Correct Failure Criteria

Design/Analysis - FEA  Solid Model Quality  Balance simplicity/accuracy Use your intuition to include features that will increase stresses Exclude trivial features  Correct Boundary Conditions  Make sure your restraints accurately represent real conditions Check degrees of freedom Check fastener/mating conditions in assemblies

Design/Analysis - FEA  Load Accuracy  What type of loading? point load? distributed load?  Am I missing loads? thermal? centripedal?  What is the magnitude? 10lbs? 500lbs? 1,000,000lbs? Rationalize with intuition Determine with testing  Material Selection  Did I select the correct material?  Are my properties in the correct units?

FEA – What to expect?

Design/Analysis - FEA  Mesh Quality  Make sure it is fine enough to accurately depict features  Affects processing time

Design/Analysis - FEA  Correct Failure Criteria Stress based: yielding or fracture? Excessive displacement Loss of function Corrosion Thermal degradation Fatigue Remember that ductile and brittle materials fail differently and have different failure criteria!

Design/Analysis  When in doubt, do some hand calculations  Mathcad and Matlab are very useful  Shigley is very useful  DANotes is a good resource as well:  Your basic calculations and FEA should support each other If they don’t, you should know why

Welds  Strength of welds  Location- sharp corners?  Loading- stress state of weld?  Size  Quality of weld!  Fatigue

Fatigue  Are their cyclic loads?  Do fatigue analysis  S/n approach used in Shigley

Safety  Pinch points?  Sanitation?  Exposed wiring?  Warnings?

Quality  Deliverables should function well  Make sure products are durable  Double-check safety

References  References:  What Kind of Analysis do you Need for your Project?, Dr. Kramer, MIME Dept.  Photo Credits:  ages/HandTools-Jacks.jpg ages/HandTools-Jacks.jpg  expecting-too-much-from-fea expecting-too-much-from-fea-0710