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Why do the stress results differ from same model and same situation?

Posted 9 oct. 2023, 23:49 UTC−4 2 Replies

H Z
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Hello dear scientists, Hope all is well! I have a very simple model,just a steel box.The fixed constraints are all at the bottom, and the boundary load is applied externally with a pressure of 0.1MPa. The only difference between the two is the positive pressure+0.1MPa in the figure above and the negative pressure -0.1MPa in the figure below. It is reasonable to say that the stress values calculated by the two should be the same. Why is there a slight difference in the actual calculation? One is 229MPa, and the other is 223MPa. https://img1.imgtp.com/2023/10/10/Ats8aFuf.png https://img1.imgtp.com/2023/10/10/g2p1A1Nw.png

2 Replies Last Post 11 oct. 2023, 21:28 UTC−4
Henrik Sönnerlind COMSOL Employee

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Posted: 1 year ago 11 oct. 2023, 05:50 UTC−4

If the stresses differ with only a sign change in the load, then there must be some nonlinearity in action. Is geometric nonlinearity activated?

If you increase/decrease the load by, for example, a factor of 5, what happens to the stress values?

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Henrik Sönnerlind
COMSOL
If the stresses differ with only a sign change in the load, then there must be some nonlinearity in action. Is geometric nonlinearity activated? If you increase/decrease the load by, for example, a factor of 5, what happens to the stress values?
H Z
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Posted: 1 year ago 11 oct. 2023, 21:28 UTC−4

If the stresses differ with only a sign change in the load, then there must be some nonlinearity in action. Is geometric nonlinearity activated?

If you increase/decrease the load by, for example, a factor of 5, what happens to the stress values?

DEAR Mr Sönnerlind: Thank you very much for reply,and your suggest really helped me,it works,the stress values become to the same,whatever the factor changed or not,they're linearity now. I just didn't notice that the default is nonlinearity in Comsol,and the most important thing is I didn't realize that nonlinear calculations would be affected by sign change, I should learn more about nonlinear theory. Thank you again. Best regards.

>If the stresses differ with only a sign change in the load, then there must be some nonlinearity in action. Is geometric nonlinearity activated? > >If you increase/decrease the load by, for example, a factor of 5, what happens to the stress values? DEAR Mr Sönnerlind: Thank you very much for reply,and your suggest really helped me,it works,the stress values become to the same,whatever the factor changed or not,they're linearity now. I just didn't notice that the default is nonlinearity in Comsol,and the most important thing is I didn't realize that nonlinear calculations would be affected by sign change, I should learn more about nonlinear theory. Thank you again. Best regards.

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