Modal Analysis: Why high stress/displacement?
Modal Analysis: Why high stress/displacement?
(OP)
Good evening, working in Workbench. Been analyzing a small plastic (Valox) gear, and was interested in modes. Where reasonable frequencies are shown in results, 6 modes within 1200 Hz to 1500 Hz, stresses and displacements are unreasonably high, 1.5 e8 PSI with lowest stress 50 KSI. With a 7500 PSI yield, it seems this gear would've exploded. This doesn't seem right... any help would be greatly appreciated. Thanks.





RE: Modal Analysis: Why high stress/displacement?
You can get menaingful stresses if you add damping to your model and then drive it with representative forces. That may well be an add-in module to your post processor.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Modal Analysis: Why high stress/displacement?
As greg suggested if you want to know something other than natural frequencies or mode shapes you'll need to do a forced response analysis or something of the sort based on the information you have at hand.
RE: Modal Analysis: Why high stress/displacement?
Thanks for the insight, will be sure to do more research on forced responses. Knew there's an obvious explanation for this.
Chad
RE: Modal Analysis: Why high stress/displacement?
RE: Modal Analysis: Why high stress/displacement?
RE: Modal Analysis: Why high stress/displacement?
RE: Modal Analysis: Why high stress/displacement?
Producing FRFs from a normal modes analysis is fairly easy in a spreadsheet.
Fairly easy...
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.