Creep Crack Growth Simulation of Ni-base Superalloy

The purpose of this study is to develop a numerical approach to simulate the creep cracking of a Ni-base superalloy. The approach is based in continuum damage mechanics (CDM) and uses the classic Kachanov-Rabotnov constitutive equations for creep deformation and damage evolution. Creep damage takes the form of defects such as microcracks, cavities, voids, etc. A numerical crack growth algorithm is developed to predict the onset of crack initiation and the successive growth of cracks via element death in the general purpose finite element software ANSYS. In this paper, the Kachanov-Rabotnov constitutive model is implemented as a user material model in ANSYS and the numerical crack growth algorithm is developed and written in ANSYS parametric design language (APDL) command code. A study of mesh size in relation to initial flaw size and initiation time is performed. A demonstration of the proposed numerical crack growth algorithm is performed and a qualitative analysis conducted. A series of improvements and parametric studies are suggested for future work.