Study of steam turbine blade degradation Part 2 - Damage mechanical model of blade materials during long term service

A damage mechanical model has been proposed from the theory of continuum damage mechanics that describes the service damage evolution of steam turbine blade materials during long term service. In the model, the damage variable is selected according to the variation in fatigue limit of the blade materials after service. Furthermore, a model of the degradation of fatigue strength during service has been created. The experimental results are in good agreement with the model. Compared with the low cycle fatigue damage model, the strength design of the blade is conservative early in its service life. If the degradation in fatigue strength is not taken into account, the life prediction of the blade is inadequate for long term service lives. (C) 2001 IoM Communications Ltd.