Relation between Stress Intensity Factors and J-integra via CINT calculation - please help
Relation between Stress Intensity Factors and J-integra via CINT calculation - please help
(OP)
Hello, I am using CINT command in Ansys v.14 to evaluate values of Stress Intensity Factors and J-integral. What is different between these two "types" of CINT command? Only change in input is in CINT,TYPE,JINT / SIFS... My problem is that theoretically there is relation between J and K (sifs) that J=K^2/E. It is for elastic problem because sifs are not defined in elastic-plastic problem. But my question is: if I create simulation with plasticity and I order Ansys to evaluate Sifs by CINT command, the relation J=K^2/E should work? I tried to create this simulation and for small-scale loading it works, but for higher loading J-integral calculated directly from CINT command does not equal with J-integral calculated from K (which was evaluated by CINT). And i guess why? Just dont be "angry" because i am using stress intensity factors in plastic simulation, i know it is not correct but i though that "numerically" the relation between J and K from CINT should work in any type of loading/materials and obviously it is not. Can anyone help me and tell me what is different between CINT for J-integral and for K-factors? Some explanation for Ansys inner routines should be helpful... Thanks a lot for everything.





RE: Relation between Stress Intensity Factors and J-integra via CINT calculation - please help
Jintegral is for Elastic-Plastic Fracture Machanics. the J = K^2/E relationship is valid for elastic loading; if your model has large scale plasticity, then i don't think you can use K and need to use a Jintegral approach. this'll be ok if you're looking for residual strength, but if you're looking for crack growth i think you're in for "a world of hurt".
Quando Omni Flunkus Moritati
RE: Relation between Stress Intensity Factors and J-integra via CINT calculation - please help
RE: Relation between Stress Intensity Factors and J-integra via CINT calculation - please help
i would expect that the J integral calc knows nothing of K; that they're working from internal stresses along a path.
i would have thought that we use the realtioanship to calc equivalent K from a J integral result.
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RE: Relation between Stress Intensity Factors and J-integra via CINT calculation - please help
From this i was expecting that J=K^2/E should work anytime, obviously it is not and i want to know why.
And rb1957 can you explain what do you mean by "equivalent K"? I am not from english speaking country and sometimes i have problems with understanding english technical expressions. Thanks.
RE: Relation between Stress Intensity Factors and J-integra via CINT calculation - please help
I expect you're running NL ANSYS ?
If you're running linear ANSYS, then you'd expect the J = K^2/E relationship to hold (since your model is elastic) ... however the results are not real (because reality is plastic).
"what is different between CINT for J-integral and for K-factors" ... have you looked at the ANSYS manuals ? the developer manual might go into this detail ? have you asked the help desk ? have you tried your model is 1% loading (ie, drive it to be elastic) ?
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