A weight function-critical plane approach for low-cycle fatigue under variable amplitude multiaxial loading

Low-cycle fatigue data of type 304 stainless steel obtained under axial-torsional loading of variable amplitudes are analyzed using four multiaxial fatigue parameters: SWT, KBM, FS and LKN. Rainflow cycle counting and Morrow's plastic work interaction rule are used to calculate fatigue damage. The performance of a fatigue model is dependent on the fatigue parameter, the critical plane and the damage accumulation rule employed in the model. The conservatism and non-conservatism of predicted lives are examined for some combinations of these variables. A new critical plane called the weight function-critical plane is introduced for variable amplitude loading. This approach is found to improve the KBM-based life predictions.