On 4/5/22 07:21, [email protected] wrote:
I tried with different mesh refinements and different time-step sizes, but the
analyses provide unsatisfactory results. By summarizing, the size of active
set reduces to zero after the first time step, and then increases. The
convergence of the Newton solver slows down since the initial loops, leading
to loose convergence (for max loop reached). The evaluation of the resulting
contact force fails giving negative values.
At the moment, I'm really stuck. Is there anybody who can give me some hints?
Giovanni,
short of finding someone who is (i) an expert in time dependent plasticity,
(ii) has plenty of spare time to look through your program, you are left with
debugging the problem yourself. Here is how I would approach things:
* Simplify. Instead of looking at a whole load history, just consider two steps.
* Pick a load history so that what step-42 produces corresponds to your first
step. Make sure you get the same result. If it doesn't, you've just figured
out that already your first load step has a problem.
* Then double the load in the second step. You know that that should result in
a larger indentation, and a larger active set.
* If it doesn't, investigate why that is. One approach would be to simplify
the set up so that instead of indenting a complex shape (or just a sphere),
you impose a constant load across the top surface of the domain. You might
even be able to compute the solution for this problem by hand because of the
symmetries of the deformation you expect.
It is not uncommon for a complex program to be wrong in the beginning -- in
fact, I'd say that's how nearly every program starts out. The question is
whether you can build the mental tools to break things down into smaller
pieces that can be debugged more easily. Simplifying the situation to
something for which it is easier to reason about the behavior is a key first
step in this process.
Best
W.
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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