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Stress free boundary

Posted Dec 21, 2010, 3:05 a.m. EST Structural Mechanics Version 3.5a 2 Replies

Chris McCorquodale
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Hi,

Is it possible to apply a stress free boundary to a model? For example, I have a model in which i am interested in the high stress region but because of the way my prescribed displacement constraints are applied the high stress region is in the wrong place. Is there any other way around this?

Thanks,

Chris
2 Replies Last Post Dec 21, 2010, 6:57 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 21, 2010, 3:53 a.m. EST
Hi
Have you tried to define your fixed constraints such that you free the stress ?

i.e. instead of a "fixed constraint, use a roller on the boundary and fix a central point (or a few along different axis)

i.e. in thermal do not fix but impose a prescriped displacement depending on a material expansion coefficient and the temperature, providede you have a central CoG for thermal expansion

i.e use symmetry planes

there are many ways around to get an isostatic support without overconstraining, and still get easily representing displacement/stress values

Note: if you constrain a corner of a cube the displacement will go all in one direction, that is not always the easiest to debug/analyse, therefore try selecting a more central "fixed point"

Finally in V4.1 you might exclude your stress representation (or any plot representation) for some regions with a "filter" subnode and geometrical bolean operations

--
Good luck
Ivar
Hi Have you tried to define your fixed constraints such that you free the stress ? i.e. instead of a "fixed constraint, use a roller on the boundary and fix a central point (or a few along different axis) i.e. in thermal do not fix but impose a prescriped displacement depending on a material expansion coefficient and the temperature, providede you have a central CoG for thermal expansion i.e use symmetry planes there are many ways around to get an isostatic support without overconstraining, and still get easily representing displacement/stress values Note: if you constrain a corner of a cube the displacement will go all in one direction, that is not always the easiest to debug/analyse, therefore try selecting a more central "fixed point" Finally in V4.1 you might exclude your stress representation (or any plot representation) for some regions with a "filter" subnode and geometrical bolean operations -- Good luck Ivar
Chris McCorquodale
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Posted: 1 decade ago Dec 21, 2010, 6:57 a.m. EST
Hi Ivar,

Thanks for this, I'll try some of the things you have suggested!

Regards,

Chris
Hi Ivar, Thanks for this, I'll try some of the things you have suggested! Regards, Chris

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