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)

Differing results:

Tabulated results:

Any thoughts on what could be going on here?