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Kexing Chen's blog

why my umat's behavior degrade in parallel mode?

I've met some strange problems implementing umat. To speak in short, it's parallel degradation, which means when run in serial mode, everything is OK, there's no failure of equilibirium iteration and therefore no cut back, but when switch to parallel mode, there are random cut backs. I checked the process by outputing results to files and found very bizarre phenomenon, the data changes when transfering from the subroutine called to its caller. For example, if the main program calles sub(a), and in sub a is specified intent(out).

Why the VVF of GTN model within Abaqus keeps 0

I calculated an example of unaxial tension using GTN model offered by Abaqus. I followed all the instructions found in CAE User's and Analysis User's manual in Abaqus documentation. No error or warning was issued but the result seemed ridiculous, since VVF, VVFG and VVFN keeped 0 throughout the process while equivalent plastic strain keeped increasing(which showed the material had come into plastic deformation). I don't know what went wrong, looking forward to you reply.

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