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[URGENT]Problem with boundaries-Solid Mechanics?

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I've been wracking my brains with this for the last few days. I keep getting a convergence error which most likely is due to an error on the boundary conditions? Attached is my file with what I have. I would be forever grateful if someone could take a quick look and tell me what I might be doing wrong with my boundary conditions.


1 Reply Last Post May 10, 2015, 3:52 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 9 years ago May 10, 2015, 3:52 p.m. EDT
Hi

for me the main issue is that you have selected Geometry "assembly" mode, this means that all your domains are independent.
To check such a model, I would have started by applying a body load => gravity and use a time dependent solver just to check that the body remains "up" as expected, you will be surprised by the result if you try this in assembly mode :)

Then you two "contact pairs" are of no use because you need continuity to hold the shoulders in place. or at least a pair BC constraint must be manually defined.

The best would be to start with 2-3 bodies and you test out the Geometry "assembly" and "union" mode to be sure you understand these: have the 3 bodies intersect (i.e. cubes somewhat overlapping each other). Then fix one boundary and apply a gravity body load and do a stationary study (turn on the plot while solving for each solver steps to monitor better what is happening ...)

--
Good luck
Ivar
Hi for me the main issue is that you have selected Geometry "assembly" mode, this means that all your domains are independent. To check such a model, I would have started by applying a body load => gravity and use a time dependent solver just to check that the body remains "up" as expected, you will be surprised by the result if you try this in assembly mode :) Then you two "contact pairs" are of no use because you need continuity to hold the shoulders in place. or at least a pair BC constraint must be manually defined. The best would be to start with 2-3 bodies and you test out the Geometry "assembly" and "union" mode to be sure you understand these: have the 3 bodies intersect (i.e. cubes somewhat overlapping each other). Then fix one boundary and apply a gravity body load and do a stationary study (turn on the plot while solving for each solver steps to monitor better what is happening ...) -- Good luck Ivar

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