Comprehensive study of the structural integrity of a damaged turbine disk using FEM, DIC and phase field methods

The aim of this study is the formation and numerical-experimental background of the approach to assessing of the structural integrity based on the principles of tolerance damage and simulation modeling. To this end, constitutive equations of the Lemaitre model and phase field fracture are employed, which include damage functions for the stages of defect appearance and crack growth. A general system of resolving equations of isotropic and kinematic hardening, viscous plasticity and damage is formed, and a method for determining the parameters of these equations is developed and implemented in the ANSIS. The proposed method is invariant to the specific form of the equations and depends only on the nature of the behavior of the continuum. A distinctive feature of the proposed approach is the validation and verification of the low-cycle fatigue and phase field models using a simulation model. Low-cycle fatigue tests with measurements by digital image correlation of the displacement and strain fields around the holes and crack tip in the simulation model were performed. The fatigue lifetime and crack growth predictions are evaluated and compared using simulation model and a damaged in service power steam turbine disc with a blade rivet attachment as a case study.