Fatigue Failure Criteria for Combined Cyclic Stress.

Failure criteria for combined cyclic stress are represented in terms of parametric families of failure surfaces in stress space. Quadratic approximations and symmetry arguments are employed in systematic fashion to construct isotropic failure criteria for general three dimensional states of cyclic stress. Particular attention has been directed to the important cases of normal stress-shear stress bending-torsion and biaxial stress cyclings. It is shown that failure criteria for cycling with and without mean stress reversed cycling have different forms, the latter admitting simpler representations. Author