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Magnetic torque?

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Hi All,
I get a very simple model attached. There is a uniform B in the big box in +Z. Then two sticks support a magnet whose magnet field is in +X. So When I applied magnetostatics (emnc) and Solid-stress (smsld) modules on it. I should see the magnet flip up under the +Z B field, which I need to show the force distribution to generate the torque. But using Maxwell stress tensor I only can get the total force. Anyone knows how I can get the force distribution along the magnet?

Thanks a lot for helping!


1 Reply Last Post 20 nov 2009, 08:24 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 20 nov 2009, 08:24 GMT-5
Hi

Have you read thrugh the documentation (p58++ and 133++ [V3.5a] acdcug.pdf) ?
There you see that you can get the Maxwell stress tensor force densities over the surfaces
the xxx_nTx_emqa etc. if you apply these to the surfaces you should get some displacement.

There are not only the absolute values xxx_forcex_emqa in there. Now take care, the meshing need to be rather symmetric and dense to get correct values out with Maxwell tensors, as the field gradients are rather dense around the magnets. You have also the virtual work approach, that I find more precise, but slightly heavier to set up. .

Therea are a few examples in the documentation too it is really useful to run them. Mostly every important case I have considered can be found in the documentation, but it's clear it takes time to read and search through all those documents, an indexer à la Google or MS helps

good luck
Ivar
Hi Have you read thrugh the documentation (p58++ and 133++ [V3.5a] acdcug.pdf) ? There you see that you can get the Maxwell stress tensor force densities over the surfaces the xxx_nTx_emqa etc. if you apply these to the surfaces you should get some displacement. There are not only the absolute values xxx_forcex_emqa in there. Now take care, the meshing need to be rather symmetric and dense to get correct values out with Maxwell tensors, as the field gradients are rather dense around the magnets. You have also the virtual work approach, that I find more precise, but slightly heavier to set up. . Therea are a few examples in the documentation too it is really useful to run them. Mostly every important case I have considered can be found in the documentation, but it's clear it takes time to read and search through all those documents, an indexer à la Google or MS helps good luck Ivar

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