It means the fracture properties vary through the part, just as the microstructure varies through the part. Analysis software almost always assumes the material is a continuum with constant material properties, which is a reasonable assumption for a part like a cylindrical shaft that has been through hardened and tempered. For a part that has been carburized case hardened, there is a gradient to the microstructure, residual stresses, and mechanical properties. These complicating factors mean that parts usually are tested physically rather than computationally.
Regards,
Cory
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