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how is the fracture stress intensity factor K caculated in ANSYS?

Chen Long's picture

dear my friends!:

 i doult whether the value of K caculated by ANSYS is proper for a cracked model with Ramberg-Osgood constitutive relationship?   

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Dear Chen,

Ansys offers mainly two methods for calculating the stress intensity factor - Interaction integral method and Displacement extrapolation method. The traditional, displacement extrapolation method is based on the nodal displacements near the crack tip. It is a post processing activity, only valid for linear elastic problems. While, the interaction integral method can support nonlinear material behaviours like Ramberg–Osgood model.

Also you should make sure that the plasticity (Ramberg–Osgood behaviour) is limited to the regions in the immediate vicinity of the crack. The parmeter - 'stress intensity factor' is based on the Linear Elastic Fracture Mechanics assumption of small scale yielding. You should be using the J-Integral based on the Elastic-Plastic Fracture Mechanics, if your model has more regions undergoing plastic deformation.

Regards, Anoop

Chen Long's picture

Thanks very much,my friend Anoop!I have another question that why both the value of Kic and Jic of a ductile material are given in any material reference books and what the relationship between the two values is! i am looking forward to your reply! thanks again!

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