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Please Translate: "Equilibrium is not achieved.  Results are saved up to the current iteration."

Question asked by John Willett on Jul 28, 2017
Latest reply on Aug 8, 2017 by John Willett

I'm running SW Premium (so only linear static simulations), either 2016 SP5.0 or 2017 SP3.0, and getting this error message after a long simulation using the Intel Direct Sparse solver.  I won't go present the model because it's a complex assembly with many contacts, both bonded and no-penetration, and I'm just looking for general guidance.  I don't understand what iterations it's talking about with a direct solver, although perhaps the iterating occurs when solving the contact constraints?  What does this message really mean?


A few details seem particularly relevant:


1) I've carefully checked all of the fixtures and contact conditions, and I'm convinced the model is properly restrained.  Both the Interference Detection and Contact Visualization Plot tools agree that the contacts are where I think they are.  I've also tried to provide adequate mesh density on all critical contact areas.  In any case, there's no explicit complaint about large displacements or insufficient restraints.


2) The only external load is gravity, one part is fixed, and all the others are either bonded or restrained with surface-to-surface no-penetration conditions, but there are (quite stiff) springs that allow (very slight) sliding along three of the no-penetration contacts.


3) The main oddity is that the study solves happily (although after a similarly long time) with gravity oriented in one direction (perpendicular to the springs, although they flex anyhow because of the torques produced by a COM offset from the fixture) but fails when gravity is oriented parallel to the springs, which should result in a much simpler, symmetric solution.  Might this mean that the study barely achieves equilibrium in the successful case but that changing the orientation pushes it just over the iteration limit?  (I assume this limit is inaccessible to me in linear static simulation.)


4) In the orientation that completes successfully, should I expect to find useful diagnostic information in the .OUT file (assuming I run it again and save that evanescent file elsewhere)?


Thanks in advance for any suggestions. -- John Willett