A Nonlocal Stress/Strain Correction Method of Notched Areas for Turbine Blades Service Life Monitoring

A nonlocal stress/strain approximation correction method based on Neuber's rule is proposed to achieve plastic correction of the linear elastic stress/strain state along the crack propagation path in the critical plane by ensuring the premise of force and moment balance. The method can quickly obtain the local stress and strain of the turbine blade notch during use. Based on the proposed method, combined with the low cycle fatigue (LCF) life prediction method based on the critical plane-critical distance, the LCF life of the notched part of the turbine blade can be predicted more accurately. The proposed method was validated using structural nonlinear finite element analysis (FEA) and experimental results for the blade tenon specimens subjected to LCF load. The comparison of computed and analyzed stress/strain revealed a good agreement. All predicted life values fall within a 3-factor scatter band when compared with the experimental life data.