Multiaxial fatigue life assessment of sintered porous iron under proportional and non-proportional loadings

Sintered metals are increasingly applied to high performance mechanical parts with limited fatigue life in the automobile industry. The present work focus on quantifying the multiaxial cyclic deformation and fatigue behavior of sintered metals under multiaxial loading conditions. The fatigue experiment includes 40 specimens under 7 strain-controlled proportional and non-proportional loadings. The cyclic deformation behavior under various loading conditions are investigated for sintered iron with density 7.2 g/cm3. The multiaxial fatigue life of the sintered metals is evaluated based on three multiaxial fatigue criteria, Smith-Watson-Tropper (SWT) criterion, the virtual strain energy criterion and the modified SWT criterion. Based on the statistic analysis of the prediction error, it is shown that the modified SWT model provides satisfactory fatigue life predictions under proportional and non-proportional loading paths. Furthermore, the cracking behavior of sintered metal is assessed with the critical plane models and discussed.