I am performing a 3D analysis of an edge cracked plate with a straight fronted crack under pure mode I loading in ANSYS APDL. And I am plotting the variation of SIFs along the crack front in the thickness direction. The SIFs are extracted from the ANSYS APDL using the J-integral (CINT) technique.
For the pure mode I there should not be any other SIFs except KI. But in my analysis, I am getting a constant negative value of KII comparable with KI along the crack front in the thickness direction.
Can anyone explain the presence of KII in pure mode I loading? It will be very helpful to understand the 3D crack simulation.
I have almost tried all the possible variations of boundary conditions but the results are same only the magnitude is changing.
For a plane stress condition you shouldn't observe KII, but if it's a thick specimen plane strain conditions apply. In that case, except for the surface, triaxial stress state would be developed in the material bcz of the plane strain conditions which can result in local KII values even with mode I load conditions
Hi Shiv Sahaya Shukla
Seconding Abhay Singh 's explanation, some minor K from other modes could be due to the plane strain condition if thick section is modelled in 3D.
Next would be, what do you mean by pure mode I opening? It could be that you've simulated a configuration with primary KI loading?
Regards,
Wee
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