Re: modal analysis for location of "weak spots"

Greg Locock <[EMAIL PROTECTED]> wrote:
> Paul_Ktop-posted &  wrote:
> > "Jeff Finlayson" <[EMAIL PROTECTED]> wrote
> >>Paul_K wrote:
> >>
> >>>Stress results from modal analysis can be used to locate weak spots, of
> >>>course remembering not to take those stresses literally but only for
> >>>comparison between different portions of the structure and only in the 
> >>>same mode.
> >>
> >>That will only be useful if the part/structure is loaded so that mode(s)
> >>gets excited.  Also, you couldn't compare a hot spot in one mode to a
> >>hot spot in another mode.

> > You are 100% right, thank you for replying. Could you direct me to some
> > published references to prove this point?
> > 
> > thanks
> > Paul

> He is not 100% right.
> 
> Fatigue analysis of structures is done successfully using FEA. This 
> implies examining the stresses due to many modes at any particular point 
> on the structure, since the waterfall plot used to excite a fatigue 
> model is based on the total signal(s) exciting the structure, not one 
> frequency at a time.
> 
> Cheers
> Greg Locock

Again, you are referring to a transient analysis, not an eigenvalue  (modal
analysis) one that is in question here.