AnsweredAssumed Answered

Linear vs. Non Linear Discrepancies

Question asked by Adam Chevalier on Jun 3, 2013
Latest reply on Jun 4, 2013 by Jared Conway

Introduction:

I've got an analysis that involves a rotating turbine wheel and a shrink-fit shaft/bushing combo.  A few years back I completed a linear analysis on the components where von Mises stresses peaked around 85% of yield.  After running the turinbe for a few years my customer came back and basically asked "just how fast can we run this before we get into trouble?".  My goal was to analyze the turbine beyond the point that linear analysis predicted yield would occur utilizing a non linear analysis.  Step 1, in my mind, was to run the non linear analysis at the same speed the linear analysis was run in order to verify that the non linear was set up and working correctly.  Getting the analysis to run was fairly difficult but with a loose enough mesh it seemed to cooperate.  Unfortunately the results between linear and non linear don't match well.

 

Components: (locations of shrink-fits shown)

assy.jpg

 

Differing results:

stress.jpg

 

Tabulated results:

 

Locationvon Mises Stress, Linearvon Mises Stress, Non Linear
Bore, near nose14789
Bore, near backface15076
Blade root, exit13371
Blade Root, inlet10838

 

Any thoughts on what could be going on here?

Outcomes