Hello everyone,
I am writing UMAT subroutine in ABAQUS to analyze constitutive models of epoxy matrix with elasto-plastic damage, but a difficult problem arises:
I first wrote elasto-plastic UMAT to analysis, the results are correct; but after adding the damage part on this basis, the load is no longer increased before the stress reaches the peak, and the damaged part does not play any role. Where did I go wrong with this question?
If the analyses crush, probably DDSDDE is wrong when damage occurs. I do not know what model you are implementing, but I would like to remember that damage causes mesh dependency and loss of ellipticity (the solution is not unique). These aspects can cause severe numerical troubles.
Good luck!
Thanks for your answer.
I want to implement an elasto-plastic damage model for one element. But when the model reaches damaged state, the calculation doesn't converge, resulting in the softened segment of the damaged state not appearing.
I wrote the Umat Subroutine according to the 'DDSDDE' given in the literatures
(http://dx.doi.org/10.1016/j.ijsolstr.2013.02.009 ; https://doi.org/10.1016/j.compscitech.2018.12.003), and I still haven't figured out what went wrong.
But also thanks to Mr.Panteghini. Andrea Panteghini
The problem has been solved. Forms of plastic strains, elastic strains and DDSDDE, must be written correctly. Thanks.
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