Analysis of unified continuum damage mechanics model of gas turbine rotor steel: Life assessment

摘要

In this research, the unified creep continuum damage mechanics model of Lemaitre is used to model the stress-strain behavior of a gas turbine rotor. The unified damage law can model the creep and low cycle fatigue damage. It is based on the increment of the accumulated inelastic strain, which may be due to either creep damage or low cycle fatigue damage. The parameters of the unified continuum damage mechanics model, including Q, Norton constants, and constants of the nonlinear kinematic hardening model are determined and optimized by cyclic tension and relaxation tests. A careful three-dimensional thermal analysis is carried out and the temperature gradient is obtained. This analysis is used to determine stresses of the gas turbine rotor. Creep and low cycle damage are also modeled and stress-strain evolution in the gas turbine rotor is obtained. The replica tests are performed on four points of the rotor surface and formation of the creep voids is verified under a scanning electron microscope. Based on the continuum damage mechanics analysis, the creep-fatigue interaction is considered in modeling and the remaining life of the rotor is estimated.