I made an UMAT subroutine about the shape memory alloys. When I applied this subroutine to a bending test with one end is clamped and the other free, it did not give any problems but when I tried to do in a 3 points-bending test the convergence did not occur.
Does anyone know why the subroutine works with one test but not with the other.
Despite the differents shapes of the simulated parts both have the same properties (of the command user material and thermals)
The files dat and inp are attached.
Thanks in advance
Dear Miguel Verona
Have a look:
1. https://www.researchgate.net/post/Can_anyone_share_an_example_of_UMAT_subroutine_for_ABAQUS
2. http://imechanica.org/files/Writing%20a%20UMAT.pdf
Kind Regards
Qamar Ul Islam
Check if you have carefully defined the Hughes-Winget algorithm, by well formulating the R(k) -increment of rigid body rotation of the local basis system- in the beginning of your UMAT. You can read more about is in documentation. Also a well written constitutive Jacobian (DDSDDE); It has a huge impact on convergence.
Pejman Shayanfard I have never heard about the Hughes-Winget algorithm, so I am going to search it in the documentation.
As you said (about the importance of DDSDDE), if I delete the actualize of the constitutive Jacobian and of the stress (as you can see in the attached image), the problem doesnt occur. However according to the Brinson algorithm these steps are necessary.
Thank you very much for your help.
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