Quantitative study of high-frequency fatigue hole-edge stresses in nickel-based single-crystal superalloy

Abstract

In this paper, the influence of air film holes on the stress distribution of nickel-based single-crystal superalloy blades is investigated, a simulated test piece is designed for the analysis and test of the stress distribution of air film holes, and a method of quantitative inverse inference of the stress at the edge of the air film holes is proposed. Finite element simulation of high circumferential vibration fatigue of the simulated test piece was carried out by ANSYS to obtain the gradient of stress distribution at the hole edge. The EBSD technique was used to measure the dimensions of the plastic zone in the region near the fracture, and the quantitative fatigue stresses were extrapolated using a crack tip plastic zone model with Tresca yield criterion. The compressive stress exerted by the femtosecond laser perforation method on the air film aperture wall was detected by the nanoindentation technique, and the residual stress was analysed using the S. Suresh computational model. The results of this study show that based solely on finite element simulation, it is not possible to completely simulate the effect of residual stresses caused by machining on fatigue fracture, which in turn leads to a lack of conformity between the results of finite element simulation and the results of the inverse plastic zone size extrapolation; however, the stress magnitude at the edge of the hole can be well computed by combining the stress concentration coefficients from finite element simulation with the stresses from the inverse plastic zone size extrapolation after taking into account the residual stresses from machining. The quantitative analysis results of this method have an error within 1.3 times the dispersion band compared to the test data.