Evaluation of Cyclic Hardening Parameters for Type 304LN Stainless Steel

Engineering components are often subjected to cyclic load excursions beyond elastic limit and hence cyclic plastic deformation of engineering materials becomes inevitable. Since the resultant elastic-plastic stress-strain response of the material plays a pivotal role in analysis, design and failure of the component, it becomes important to understand the cyclic plastic deformation behaviour of engineering materials. Also, cyclic hardening parameters are required in the design of structural components subjected to large plastic deformation. Constitutive equations were proposed by Prager, Armstrong and Frederick, Chaboche, and Ohno-Wang based on the stabilized strain-controlled hysteresis curve to evaluate the hardening parameters. In the present study, cyclic hardening parameters for SA 312 Type 304LN stainless steel have been determined based on the results of constant amplitude strain-controlled fatigue tests carried out earlier at CSIR-SERC under five different strain amplitude values, viz, 0.20%, 0.35%, 0.65%, 0.80% and 0.95%. It is observed that in isotropic hardening, the values of Q decreased with increase in strain amplitude. In kinematic hardening, the values of C1and γ1 are constant for all values of strain amplitude.