TS-99 Residual Life Assessment Based on Crack Growth Analysis of Gas Turbine First-Stage Nozzles(Session D-5 Maintenance and Control 2)

概要

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A method of evaluating material degradation and analyzing crack growth was discussed to develop a residual life assessment method for the first-stage nozzle of a gas turbine. Outer wall and trailing edge cracking were mainly observed in the nozzles inspected. These cracks were thermal fatigue cracks propagated with start-up and shut-down of turbine, therefore severer cracking was observed in DSS (Daily start-up and shut-down) operation than WSS (Weekly start-up and shut-down) mode. Fracture ductility determined by a small punch test shows a good correlation with fracture toughness of the nozzle material and this method was found to be suitable to evaluate the degradation of the nozzle. A crack growth analysis method considering a compressive strain hold effect was proposed. The predicted crack growth behavior coincided with inspection data closely. A simplified method of predicting crack growth was also proposed and verified by using the inspection data.
公益社団法人日本ガスタービン学会の論文
1999-11-14