Methods of Computational Determination of Growth Rates of Fatigue, Creep, and Thermal Fatigue Cracks in Poly- and Monocrystalline Blades of Gas Turbine Units

The crack growth kinetics of fatigue, creep, and thermal fatigue cracks in blades of gas turbine units is studied through a direct three-dimensional finite-element stepwise modeling of the crack propagation process. Prediction of crack growth rate involves the use of the criteria based on stress intensity factors (or J-integrals) for fatigue cracks, on C (*)-integrals for creep cracks, and on a combination of stress intensity factors (or J-integrals) and C (*)-integrals for thermal fatigue cracks. The authors discuss the methods for determination of fatigue life of polycrystalline blades as well as some special features of calculations of the crack growth kinetics in monocrystalline blades. The paper presents some examples of results of finite-element calculations of the fatigue, creep, and thermal fatigue crack growth processes in rotating blades of gas turbine units.