Greetings
i used interface Vumat with Umat for simulating CEL problem, after 50% of analysis, i got the error as “Excessive incremental rotation of the elements in element set ” i researched the meaning about this error in literature but h couldn’t find how fix it. Anybody can help me and advise.
Regards
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Hello Elfattah,
most probably your time step is too large. You can arbitrary decrease it with the “time scale factor” (maybe other name) in the “Step” module.
I recommend you should familiarize yourself with the theory of the CEL method. This might help you to solve the problem related to these error messages related to the CEL method in ABAQUS.
Best regards
Johannes
Dear Labenski
thank you for response, CEL depend on fixing the the mesh in space, so the distortion shall not be developed. i tried to reduce the time and mesh size, but the error is displayed after about 25 % instead of 50 % of analysis. Noted I used interface Vumat/Umat by Britta Bienen
Actually the mesh is not fixed as you might expect. The CEL method consists of three steps. In one step, the “fixed” mesh will be deformed according to the load and the corresponding material response. In a latter phase the deformed mesh will be resetted to its initial position, i.e. as user you think the mesh is fixed in space.
So reducing the time step with the time scaling factor (see image: https://imgur.com/a/kEHLYRy) usually worked for me to resolve this problem with CEL simulations. By standard I use a time scale factor of 0.9, but sometimes you may need even smaller factors. Of course, the computational time is increasing if you decrease this factor.
I see, i have already tried to use time scale factor to 0.5 and 0.85, but the error is displayed after about 25 % instead of 50 % of analysis. in addition, i tried too reduce the mesh size but i still receive the error. this error appear when i use Vumat. in contrast, the analysis has complete using anther constitutive law such as Mohr Coulomb or cap plasticity with the same model.
Did you receive this error before for CEL model ? and do you think that there problem in Vumat/Umat interface ?
I am using the Vumat-Umat interface for vibratory-pile installation simulations without problems. In most cases I could resolve this error with the time scale factor. You should also check if your boundary conditions are defined correct. You should only define boundary conditions you really need. Do not constrain all DOF at all boundaries, if you don’t need to.
the error element is existing at symmetry face near the contact zone
in addition, the energy balance is not normal. because the dramatically decreasing of total energy is occurred and the internal energy is very low. Noted, there is message state the the stretch element instead of gradient deformation
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Frank