Influence of 3D printing on compressor impeller fatigue crack propagation life

Abstract

Taking a compressor impeller with a pressure ratio less than 3 as the research object, the influence of 3D printing on the fatigue crack propagation life of the compressor impeller is analyzed under the combined action of 3D printing residual stress and external load. The impeller is printed by selective laser melting (SLM) technology. Finite Element Method (FEM) is used to simulate the 3D printing process of the impeller, and the residual stress, residual deformation and other mechanical quantities are comprehensively analyzed. The numerical simulation results are in good agreement with the crack location in 3D printing experiment. The heat treatment and numerical simulation of the printed impeller significantly reduce the residual stress. According to the experimental results and the magnitude and direction of the first principal stress, the position and orientation of the macroscopic crack are determined. The FEM of linear elastic fracture mechanics (LEFM) and the Forman-Newman-de Koning (FNK) model are used to give the propagation law and fatigue crack propagation life of the cracked compressor impeller under different working conditions. The results show that the crack initiation position is affected by the maximum residual stress of the printed impeller after heat treatment. When only the external load is applied, the stress intensity factor (SIF) of the initial crack front varies with the rotational speed as a quadratic power. When the external load and 3D printing residual stress act at the same time, the law will no longer be satisfied. The general trend of the crack propagation path is along the radial direction. The speed has a linear influence on the critical crack size and a nonlinear influence on the fatigue crack propagation life. The research work in this paper can provide a basis for damage tolerance analysis of 3D printing compressor impeller, and also provide a reference for maintenance work.