Hallo,
i want to know How abaqus calculates Von Mises stress at integration points. When i use Von Mises Stress equation or Equivalent Stress:
Svm= sqrt(1/2) * sqrt[ (S1-S2)^2+(S2-S3)^2+(S3-S1)^2 ]
i get different value than abaqus.
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*****Please write me the equation how abaqus calculate it or any refference.
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Please be specific to the point while answering!
Thanks in Advance
Hello Tamer,
I think your equation should be written as follows:
Svm= sqrt(1/2) * sqrt[ (S1-S2)^2+(S2-S3)^2+(S3-S1)^2 ]
Abaqus uses the following equation to calculate the von Mises stress:
Svm = sqrt(1/2) * sqrt( (S11-S22)^2 + (S22-S33)^2 + (S33-S11)^2 + 6*(S12^2+S13^2+S23^2) )
where S11, S22, S33, S12, S13, and S23 are stress components (not principal stress components S1, S2, and S3).
You can find the above equation in the attached pdf file (Writting a UMAT page L6.75).
Assuming that S1, S2, and S3 are principal stresses, the above equation can be also written in the following form:
Svm= sqrt(1/2) * sqrt[ (S1-S2)^2+(S2-S3)^2+(S3-S1)^2 ]
You can see both forms of the von Mises stress in the attached file (file 01.pdf).
Best,
Farid
The correct form of von Misses Stress equation or Equivalent Stress:
Svm= [(1/2)*{(S1-S2)^2+(S2-S3)^2+(S3-S1)^2}]^(1/2)
or
sqrt[(1/2)*{(S1-S2)^2+(S2-S3)^2+(S3-S1)^2}]
i guess wrting it in the formate was a bit tough for me. i am using scilab there the equation is correctly written.
@ Farid Alisafaei : Thank you for the information. the equstion used depends on Princibal stress. However the equation you write is in the general form and it works thank you!
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