I made a model that has one tube inside the other. In the outer tubes there is a force that approximates the contact between both. I’m only using shell elements (S6). The two surfaces are the same element size. The tubes are centered.
The model is not converging. Please, could someone help me?
I’m using:
surface behavior (Hard), Friction (0.3)
Contact pair (Node to surface), small sliding (No), Adjust (No)
You could, for example, try adding a separate step (before the current one) in which contact will be established by pressing the outer cylinder (with prescribed displacement in cylindrical coordinate system) towards the inner one.
Be carefull though with succesive steps in combination with shell elements. I have experienced weird behaviour when trying to solve multiple steps in a shell model as is discussed in this thread: Load Case Creation - General Questions - PrePoMax
Maybe using Amplitude instead of separate step would be a workaround?
but, it seems the values of geometry and thickness are small enough in tolerance?
geometry : 6.59-6.548 = 0.042 (mm)
tolerance : 1.84*2.5% = 0.046 (mm)
This is a simplified version that works.
Start from here and try to recover your original model set up introducing changes one by one. You will realize what was failing and how each change affects the result.
@Matej. Changing the Friction makes prepomax to crash.
I would need some more info about that. A .pmx file would be the best, and the description of the steps that led to the crash. I could not reproduce this behaviour on my own.
I know it is possibly late but I would definitely try to use the symmetry if applicable. It is especially beneficial in cases involving contact since it prevents the rigid body motion and reduces the model size.
