August 22, 2023 at 1:40 pm
henriquegpo
Subscriber
Hi Peter,
 
I would like to once again thank you for such fruitfull insights. Also thanks to the other colleagues for the help!
 
I manage to get the analysis to converge following what you said: coarser mesh and auto substepping. I have also tweaked a bit more the contact definition, making use of Normal Lagrange formulation, Nodal-Projected Normal from Target detection and Flipping contact/target edges.
 
There are a few further questions I would like to ask:
  1. I am not entirely sure why a coarser mesh is helpful. I thought that, if the elements had a decent aspect ratio (square elements), than the size itself would impact mainly on the “resolution” of the analysis. What I am imagining here is that, as this is a nonlinear material model, when the plastic strain reaches a certain limit, the tiny elements cannot keep its shape, therefore bigger elements would perform better. Is that correct?

  2. I would like to have a somewhat decent stress evaluation from that model, especially around the contact interface. Using a coarser mesh can sometimes lead to a non-uniform stress distribution plot. So this seems to be the case that a compromisse between being able to simulate and exctrating accurate stress results must be make, right?

  3. I am not yet at a point that I would like to include the thread geometry in the model, but I would like to have an estimate of how much force would rise at the threads in this condition. Is the force reaction from the fixed support a good estimation?

Still on mesh size topic, I tried to reduce it to see what would be the lower limit with which the simulation would still converge. I noticed that there is an intermediate limit, from which the simulation still converges despite of errors popping up. The error was of highly distorted elements, leading to bisection. And there are also notes of the incremental plastic strain being larger than a criterion, also leading to bisections:

Are the simulation results still valid on that case (convergence achieved despite errors leading to bisections)? Is there any aspect I should keep an eye on when that occurs?