A PATH‐INDEPENDENT PARAMETER FOR FATIGUE UNDER PROPORTIONAL AND NON‐PROPORTIONAL LOADING

Abstract

Abstract— A path‐independent multiaxial fatigue damage criterion is proposed based on critical plane concepts: fatigue crack growth is controlled by the maximum shear strain, and an important secondary effect is due to the normal strain excursion over one reversal of the maximum shear strain. The effect of loading path on fatigue endurance is quantified by the normal strain excursion. Only one multiaxial material constant is required in the model which can be determined from uniaxial test data plus one torsional result. The parameter can be easily integrated with a shear strain‐life relationship to predict low cycle fatigue lifetime. Experimental data of four different materials: En15R steel, 1% Cr‐Mo‐V steel, 304 stainless steel, and 316 stainless steel at two temperatures were used to verify the criterion. It is shown that the proposed parameter can satisfactorily correlate test results for various proportional and non‐proportional straining paths.