Fatigue Crack Growth of Multiple Load Path Structure Under Combined Fatigue Loading: Part I — Numerical Simulation

A new numerical method for the analysis of fatigue crack growth in the multiple load path structure under low-high cycle combined fatigue (L-HCCF) loading is proposed in this paper. Firstly, vibrational stress is obtained through dynamic response analyses considering joint dry friction between the turbine blade and the turbine disc based on equivalent linearization and micro-slip model. Then, the crack growth in the fir-tree attachment is simulated under vibrational stress superimposed with low cycle fatigue loading through fracture mechanics (FM) analysis. Vibrational loading in the fir-tree attachment is redistributed with the crack propagation because of this multiple load path structure. Thus, dynamic response analysis is re-performed on the turbine attachment. At last, the crack growth life of multiple load path structure under L-HCCF loading is predicted based on the linear cumulative damage model. The predicted life agrees well with the experimental data of actual turbine component, which verifies that the new numerical method for the analysis of fatigue crack growth in the multiple load path structure under L-HCCF loading is reasonable and feasible.