Dear professor and friends：
At present, I am using the UMAT program downloaded in the forum. I have not made any modification to the downloaded program itself to simulate a model of sand under gravity. First, I select the solid element (c3d8) to model the sand, and the bottom is fully constrained. The analysis steps are: static general, which is used to apply gravity load, (when P-T is set to 0), but the analysis results report errors due to non convergence, I adjusted the parameter P-T, as shown in the figure, so the convergence problem can be solved, but the results show that the established cylindrical sand model does not produce obvious compression deformation under the action of gravity, so I think the adjustment of parameter P-T can strengthen the stiffness of sand, which is obviously inconsistent with the actual situation. So I have two questions: (1) can the downloaded hypo sand UMAT be directly used for simulation without modification; (2) how can the convergence of the model be solved when P-T is 1kPa;(3. After that, I will add a steel cylinder and add a dynamic implicit analysis step based on the gravity analysis step to simulate the dynamic analysis under earthquake. Therefore, I think the internal sand should have obvious deformation, otherwise the acceleration response at the bottom and top will have no amplification effect. Is my understanding correct?
I look forward to the reply of professors and friends to help me solve this problem.Sincerely look forward to your reply, thank you very much.
