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No Convergence in Simulation With No Sharp Corners

Question asked by John Willett on Dec 14, 2015
Latest reply on Mar 31, 2016 by John Willett

I can't get this model to converge in spite of having filleted the presumed-relevant corner to remove the potential singularity.  It is shown here face-on to a symmetry cut after an h-adaptive loop of 8 cycles:

Stud Test 5_16 Fillet Half Less Interf.jpg

(The stress range for the plots was deliberately set to the yield level of the stud.)  This is intended to model a bolt threaded into a pair of test blocks, using a shrink fit to simulate the threaded joints.  A horizontal force is applied to the blocks, and vertical motion of the blocks is not allowed, so that the stud is bent into an "S" shape..  Only one quarter of the model is shown because I used symmetry across the X-Y plane and anti-symmetry across the middle of the stud to reduce the computational load.  The full model (before the symmetry cuts) is shown here for clarity:

Stud Test 5_16 Plain Fillet.jpg

Here's what happens when the mesh resolution is increased using the h-adaptive default settings:

Stud Test 5_16 Fillet Half Less Interf Convergence.jpg

This behavior is not caused by some instability of the h-adaptive method but has been replicated with manual mesh resolutions set by mesh controls.  It also has not improved by addition of the fillet; similar stress increases at the edge where the stud emerges from the block were observed without it.  The stress increases without limit on the compressed side of the stud here:

Stud Test 5_16 Fillet Half Less Interf Stud.jpg

...and on the upper edge of the fillet inside the hole in the block here:

Stud Test 5_16 Fillet Half Less Interf Block.jpg

These stress maxima are near the location where the interference ends between the two parts.  Here are the study properties:

Stud Test 5_16 Fillet Half Properties.jpg

 

Stud Test 5_16 Fillet Half Properties 2.jpg

(I haven't tried fiddling with the "Accuracy bias" setting, nor have I tried the p-adaptive method.)  Attached is a P&G in case you want to look in greater depth.

 

Can anyone suggest what I'm doing wrong? -- John Willett

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