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Displacement due to point contact
Posted Mar 30, 2016, 9:53 a.m. EDT Geometry, Mesh, Studies & Solvers, Structural Mechanics 2 Replies
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I want to simulate how a planar surface is depressed by the weight of a overlaying sphere (gravity loading) in Structural Mechanics Module. Both sphere and planar surface are expected to be in point contact. First I attempted a 2D version of this problem using circle and a rectangle as shown in attached figure. The bottom boundary of the rectangle is constrained while a body-force is applied on the circle. There is no issue with the mesh. But when I run the Study, Comsol simply gives an error message:
Failed to find a solution.
The relative error (0.69) is greater than the relative tolerance.
Returned solution is not converged.
- Feature: Stationary Solver 1 (sol1/s1)
To finalized the circle and rectangle geometry, I tried both "form union" and form "assembly options" but no success. The problem seems to be the "point-like contact" between the circle and the rectangle which is creating some singularity and preventing the solution from converging. The solution can be made to converge artificially by introducing a small boundary overlap between the circle and the rectangle. This I have tested without any issue by moving the rectangle upwards by a small amount so that there is a finite overlap between circle and rectangle. This also shows that problem is setup correctly. The solution fails only when the two domains are in 'point-like' contact. This is something I did not encounter before. I would like to know if there is robust and fool-proof way to handle point-like contacts/boundaries between the objects in COMSOL? It is possible that I am missing something very trivial, but I would greatly appreciate if any of you could share your valuable insight.