CEL analysis using hypo plasticity Vumat

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

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 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.