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How to storage UMAT output and make them input?

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Joined: 9 years ago

Hello everybody!
Its the first time I decide to write a post in the forum, I hope you can help me. Im a student working on my master thesis, the aim of the thesis is to implement a fatigue model for glass fiber reinforced composites using ABAQUS.

I am writing a UMAT in order to give material informations and properties degradation with number of cycles, it seems to work: its the first time I write a UMAT, I only tested it with a single element (reduced integration) with a tension load.

The big problem is how to write output results and make Abaqus read them for the next cycles: I need to save about 10 parameters (giving me information about the degradation of properties in that cycle) for each integration point, this parameters must be processed in the next cycle, after a pyton script will give me the number of cycles I can jump in order to have a right balance between computational effort and accuracy.
It was suggested me to store them in an external file, but I read on this forum it was not a good idea. If I decide not to use an external file (for example a text file) how can I store them? The problem is that, after a single cycle and the evalution of damage variables, I have to restart a completely new analysis and make these variables read by Abaqus as input.
The other problem is that my UMAT writes the results three times in the output file (the first two times theyre all 0 and Nan, I think theyre not converged, the third time they are acceptable). There is a way to make the results written only when convergence is reached?

Thanks in advance for your help, unfortunately my supervisor has not enough time to dedicate to me and I really dont know what to do...

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Posts: 3998
Joined: 5 years ago

Sounds like an interesting project. Unfortunately I think your only solution is to use an external file to transfer that information between runs...


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