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Definition of von Mises stress
Posted Jun 10, 2015, 6:06 p.m. EDT Structural Mechanics Version 5.0 3 Replies
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Hi all,
I have a question about von Mises stress used in the structural mechanics. According to its definition, von Mises stress can be computed using the formula, in 2D application :
σvm = sqrt ( ( σxx)^2 + (σyy)^2 - σxx*σyy +3(τxy)^2 ),
where σi,j is either normal stress or shear stress.
But when I compare von Mise stress computed from the formula above and von Mises stress generated by default by COMSOL, the value is different. I'm quite surprised as well as confused. So I'm wondering whether COMSOL uses a different formula.
Thx for your advices
I have a question about von Mises stress used in the structural mechanics. According to its definition, von Mises stress can be computed using the formula, in 2D application :
σvm = sqrt ( ( σxx)^2 + (σyy)^2 - σxx*σyy +3(τxy)^2 ),
where σi,j is either normal stress or shear stress.
But when I compare von Mise stress computed from the formula above and von Mises stress generated by default by COMSOL, the value is different. I'm quite surprised as well as confused. So I'm wondering whether COMSOL uses a different formula.
Thx for your advices
3 Replies Last Post Jun 11, 2015, 10:56 a.m. EDT
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Posted:
9 years ago
Your formula only holds if σzz=τxz=τyz=0 , i.e. in a plane stress case. You may want to check whether you set up your model as plane stress. The default in COMSOL is plane strain.
Best,
Jeff
Best,
Jeff
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Posted:
9 years ago
Your formula only holds if σzz=τxz=τyz=0 , i.e. in a plane stress case. You may want to check whether you set up your model as plane stress. The default in COMSOL is plane strain.
Best,
Jeff
Hi Jeff,
My model is 2D, so I think this formula can apply. But I don't really get it when you say I should set up the model as plane stress. Where can I change this setting. Could you explain some more? Thank you
Yuankang
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Posted:
9 years ago
I did not mean to imply that you should set up your model as plane stress. Rather, I pointed out that the formula you mention only applies in the plane stress case. If you set up your model as plane strain, the formula does not apply.
Whether you should set up the model as plane stress or plane strain depends on the situation you are trying to model; I leave that decision to you. Just don't expect your formula to apply if you set up the model as plane strain.
Whether you should set up the model as plane stress or plane strain depends on the situation you are trying to model; I leave that decision to you. Just don't expect your formula to apply if you set up the model as plane strain.