Modeling the Tertiary Creep Damage Behavior of a Transversely-Isotropic Material Under Multiaxial and Periodic Loading Conditions

Abstract

Despite the advent of single crystal turbine blades, the aerospace and industrial gas turbine industries have continued to use directionally-solidified turbine blades due to higher manufacturing yields. These transversely-isotropic turbine blades are subjected to high temperature multiaxial cyclic loading conditions which lead to complex creep strain histories. Few tensor-based constitutive models have been developed that accurately model creep-damage behavior. This paper describes an anisotropic tertiary creep damage model for transversely-isotropic materials. The model is a tensorial expansion of the Kachanov-Rabotnov isotropic creep damage formulation. The analytical techniques required to determine the associated material constants are derived and demonstrated. The model is shown to accurately model a directionally-solidified Ni-base superalloy. A parametric study under biaxial and hydrostatic loading is conducted and the resulting creep strain tensor is evaluated. A series of periodic loading simulations are conducted to examine the stress-strain behavior and damage evolution during ratcheting.