Life Assessment of a gas turbine rotor using a unified continuum damage mechanics model

In this research, the unified creep continuum damage mechanics (CDM) model of Lemaitre was used to model the stress – strain behavior of a gas turbine rotor. The unified damage law can be applied for the creep and low cycle fatigue damage. It is based on the increment of the accumulated inelastic strain which can be due of creep damage or the low cycle fatigue damage. The parameters of the unified CDM model, including Q and Norton constants, and constants of the nonlinear kinematic hardening model were optimized and determined by cyclic tension and relaxation tests. Creep damage was modeled and stress – strain evolution in the gas turbine rotor was obtained. A careful three dimensional thermal analysis was carried out and the temperature gradient, which was used to determine stresses of the gas turbine rotor, was obtained. The Replica tests were done on the four points of the rotor surface and the formation of the creep voids was verified under a SEM. Based on the CDM analysis, the creep-fatigue interaction was considered and the remained life of the rotor was estimated.

Keywords:

Continuum damage mechanics , Creep , Low cycle fatigue , Replica , Gas turbine rotor , Lemaitre’s Model ,