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Force Calculation between 2 Magnets and Displacement

Posted 27.07.2021, 05:39 GMT-4 Low-Frequency Electromagnetics, Structural & Acoustics Version 5.5 2 Replies

Christopher K
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Hello everyone,

I'm pretty new to COMSOL and tried to calculate the displacement of one Magnet. After running the program the results for the direction and the magnitude of the displacement is completly wrong. The first step I was doing ist to make the mesh a lot smaller to get rid of the direction problem, but this did not help.

What happend in my program? And what am I doing wrong? I've looked a lot in this forum but couldn't get an answer for my problem.

Thank you for your help, Christopher

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2 Replies Last Post 28.07.2021, 09:00 GMT-4
Mark Harradine
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Posted: 3 years ago 27.07.2021, 07:44 GMT-4

Your model only has a mesh for the mechanical aspects. The mfnc physics requires a mesh to contain the whole model problem (unlike mechanical models, magnetic models require a domain defined that contains the whole problem and within which the magnetic solution can be calculated).

I would suggest you build a very simple magnetic only model to understand the intricacies of obtaining accurate force results for 2 magnets (hint: use fillets on all edges and define a very fine mesh on the boundaries of the magnet domains).

The attached may be a good starting point. As Force is calculated with the Maxwell stress tensor, it is VERY mesh dependant, and the sharp edges on the attached model are also not desirable (use fillets).

Your model only has a mesh for the mechanical aspects. The mfnc physics requires a mesh to contain the whole model problem (unlike mechanical models, magnetic models require a domain defined that contains the whole problem and within which the magnetic solution can be calculated). I would suggest you build a very simple magnetic only model to understand the intricacies of obtaining accurate force results for 2 magnets (hint: use fillets on all edges and define a very fine mesh on the boundaries of the magnet domains). The attached may be a good starting point. As Force is calculated with the Maxwell stress tensor, it is VERY mesh dependant, and the sharp edges on the attached model are also not desirable (use fillets).

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Christopher K
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Posted: 3 years ago 28.07.2021, 09:00 GMT-4

Hello Mark,

First thank you for your quick reply! Unfortunatly I don't have the 5.6 Version. Only 5.5, maybe you can downgrade your file and attach it again?

I tried now to do the fillets on the magnets. But still the dispalcement of the Magnet 1 is in a strange direction. Also if I change the vector of the Remanent Flux Direction from 1 to -1 for the y-component only the magnitude of the displacement is slightly changing, not the direction.

Thanks for your help, Christopher

Hello Mark, First thank you for your quick reply! Unfortunatly I don't have the 5.6 Version. Only 5.5, maybe you can downgrade your file and attach it again? I tried now to do the fillets on the magnets. But still the dispalcement of the Magnet 1 is in a strange direction. Also if I change the vector of the Remanent Flux Direction from 1 to -1 for the y-component only the magnitude of the displacement is slightly changing, not the direction. Thanks for your help, Christopher

Attachments:

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