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Simple ball compression with contact

Posted Mar 9, 2020, 8:45 a.m. EDT Structural & Acoustics, Structural Mechanics Version 5.4 1 Reply

Arthur Biomedical Engineering
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Hello everyone,

I am trying to solve a simple Solid Mechanics model in which I want to compress a ball in between two plates. The ball and plates are in contact, but for some reason the model takes forever to solve or returns with an error. I always have this problem as soon as I introduce contact between geometries.

I have uploaded the model below. I hope someone can tell me what I am doing wrong.

Thanks a lot!

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Avk
1 Reply Last Post Mar 9, 2020, 10:55 a.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 4 years ago Mar 9, 2020, 10:55 a.m. EDT
Updated: 4 years ago Mar 9, 2020, 11:09 a.m. EDT

Hi,

Your model is severely underconstrained. The ball can roll in arbitrary directions, and the upper plate is free to float in the vertical direction. Once contact is established, this may not be a problem, but then some friction would also be needed to avoid that the ball slides.

Also, the fixed constraint at a point in the ball will create a singularity, where the material model will break down if you were to get that far.

I suggest that you add a suitable set of springs to suppress the singularities. This is discussed in the user´s guide. Also, employing symmetry will both speed up the analysis and stabilize the model. .

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Henrik Sönnerlind
COMSOL
Hi, Your model is severely underconstrained. The ball can roll in arbitrary directions, and the upper plate is free to float in the vertical direction. Once contact is established, this may not be a problem, but then some friction would also be needed to avoid that the ball slides. Also, the fixed constraint at a point in the ball will create a singularity, where the material model will break down if you were to get that far. I suggest that you add a suitable set of springs to suppress the singularities. This is discussed in the user´s guide. Also, employing symmetry will both speed up the analysis and stabilize the model. .

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