I am currently trying to implement a two scale finite element problem in ABAQUS.
The two scales are coupled through a UMAT for the macroscale. The UMAT's only job is to run a python script which runs the microscale model, carries out computational homogenization and returns the stress vector and jacobian to the UMAT.
The algorithm is working fine but there is a problem which randomly appears.
Sometimes, when the microscale model is run, abaqus gets stuck in pre.exe. There is no error and it does not stop. Even if I leave for a whole day, it does not proceed to standard.exe. I can see pre.exe open in task manager. Also, the problem does not appear for the microscale model associated with the a specific macroscale element or at a specific macroscale time. It happens randomly.
Has anybody else encountered such a problem?
I will appreciate if someone can tell me what can be the possible reasons for it?
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I presume I'm far too late to help you solve your problem, but I wanted to post my solution since there seem to be no other forum posts addressing this issue. I encountered the same issue you describe while trying to generate a preload on an axisymmetric model of a bolt; no warnings or errors, only the log file sitting at "Run pre.exe".
In my case, the model was created on the x-z plane; the standard for CAX elements is actually for x as the radial and y as the vertical direction. After rotating my model into the x-y plane, Abaqus ran without issues. Hope this helps someone out there.