Modeling of the Constitutive Behavior of Inconel 718 at Intermediate Temperatures

Turbine disks are of large importance to turbine designers as they are exposed to hot environment and subjected to high loads. In order to analyze such components with respect to fatigue crack initiation, the work generally starts with a rigorous analysis of the first few cycles, during which an important stress redistribution will always take place in an inelastic structure. In this work, the nonlinear kinematic hardening law by Ohno and Wang (1998, “Constitutive Modeling of Cyclic Plasticity With Emphasis on Ratchetting,” Int. J. Mech. Sci., 40, pp. 251–261) has been used in combination with an isotropic softening law for describing the initial stress-strain distribution for strain controlled uniaxial tests of the material Inconel 718. Focus has been placed on finding a simple model with few material parameters and to describe the initial softening and the comparatively small mean stress relaxation observed during the material testing. The simulation results obtained by using the model fit the experimental results well.