Convergence Error

[EbrahimGamaleldin]

Hello Everyone,

I am modeling soil-foundation interaction with the use of ABAQUS Standard Solver. The foundation is modeled as a rigid body with applying displacement at the reference point.
To give you an idea about the model, in the model I have to apply displacement and rotation on the foundation to achieve these criteria as shown in photo:
1. Applying the horizontal displacement until failure of soil happens, and then
2. Applying rotation to reach the maximum rotation can happen and the corresponding moment.
Therefore, larger deformations are expected to occur.

I have a few questions:
1. The implicit solver gives me an error with too many attempts made for this increment in case of Horizontal Displacement step. I tried changing I and increment number and size and not solving. Should I transfer the model to be solved with explicit one!

2. What is the best way to simulate these criteria of failure: Using one step and define the horizontal displacement and in the second step (Rotation) I modify the boundary condition, and if used this method should I modify the horizontal displacement in the (Rotation) Step=0 or keep it t as the previous!!

Thanks to you all,

 

[FEA way]

There can be many reasons for non-convergence. Switching to explicit is usually the last resort. You should try debugging the model in implicit first. Adding some stabilization/numerical damping often helps.

If you leave a boundary condition unchanged in the second step, it will keep acting (preventing the DOFs it's applied to from moving). If you deactivate it, it will be removed and replaced with equivalent forces (BC removal is done with the same default amplitude as the BC application).