Predicting high-cycle fatigue strength and three-dimensional fatigue crack growth in simulated compressor blade by phase-field model

Abstract

High-cycle fatigue is a major concern for aeroengine compressor blades under complex cyclic mechanical and aerodynamic loads, but predicting fatigue behavior of blades remains challenging. Herein, a phase-field fatigue fracture model is applied to simulate the high-cycle fatigue behavior of the simulated compressor blade. In the phase-field model, a logarithmic degradation function is adopted to describe the fracture toughness decreasing with fatigue cycles. Cyclic loads are mimicked by the pressure applied on the blade surface. The three-dimensional (3D) fatigue crack propagation of the simulated blade is simulated. It is found that the fatigue crack initiates at the variable cross-section and propagates horizontally. Laser shock peening (LSP) is further shown to improve the fatigue properties, i.e., LSP induced compressive residual stress results in a 95% increase of fatigue life and notably retards the 3D fatigue crack growth. For the fatigue strength of both the original and LSPed blades, the predictions are within the $\pm 5\text{\%}$ error band. The phase-field model here provides a predictive approach for the evaluation of high-cycle fatigue behavior and shows a great potential in the optimal design of durable and reliable compressor blades.