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A negative value of J integral before cracking

Posted 2023年5月16日 GMT-4 18:40 1 Reply

dingchuan xue
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Hi all, I wonder if you have ever got a negative value when computing the J integral? In structure mechanics module, I add a thermal strain which can evolve with time. In this case, the J integral is a negative number. It seems that the thermal strain affected the computational process. Any solution to this problem?

1 Reply Last Post 2023年5月22日 GMT-4 07:50
Henrik Sönnerlind COMSOL Employee

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Posted: 2 years ago 2023年5月22日 GMT-4 07:50

The derivation of the standard path independent J-integral makes use of the fact that the stress tensor is divergence-free. This rules out (most) body loads, as well as thermal strains.

A correction term (a surface integral) is needed. You can find an expression for this term (Eq. 26) in https://www.researchgate.net/publication/200092866_Numerical_Aspects_of_the_Path-Dependence_of_the_J-Integration_in_Incremental_Plasticity .

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Henrik Sönnerlind
COMSOL
The derivation of the standard path independent J-integral makes use of the fact that the stress tensor is divergence-free. This rules out (most) body loads, as well as thermal strains. A correction term (a surface integral) is needed. You can find an expression for this term (Eq. 26) in .

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