Biaxial Low Cycle Fatigue Behavior and Martensite Formation of a Metastable Austenitic Cast TRIP Steel Under Proportional Loading

In this paper the biaxial low cycle fatigue behavior under proportional loading of a recently developed metastable austenitic stainless cast steel is presented. Total strain controlled tests were carried out on a 250 kN biaxial servohydraulic tension-compression testing machine equipped with a biaxial orthogonal extensometer to measure the principal strains in the gauge area of the used cruciformspecimens. The principal stresses were determined based on the compliance after the load reversals. The low cycle fatigue behavior under biaxial synchronous loading is compared to the uniaxial behavior. Therefore, biaxial single step tests and a biaxial multiple step load increase test were carried out. The dependence of the stress state on the cyclic deformation curves, cyclic stress-strain curves and the formation of martensite are described. Finally, the fatigue life relationship according to Basquin and Manson-Coffin was determined and compared to the Smith, Watson and Topper damage parameter, which provides a satisfactory fatigue life prediction.