Fatigue Life Prediction of an Impeller Based on Fracture Mechanics

Welding structure is widely used in impellers fitted on the large centrifugal compressor and the crack propagation life prediction is studied based on the fracture mechanics. First the finite element structure strength analysis is carried on the three-dimensional entity model of the impeller, and the dangerous area of the structure is determined. Then based on the mechanical similarity and geometric similarity principles, a simplified two-dimensional model of the dangerous area is established. According to the simplified model, the stress intensity factors of two typical kinds of the center crack and the edge crack are calculated and functions of the stress intensity factor changed with the crack length are obtained. Finally, using the mixed mode crack propagation model, the fatigue crack propagation life of the edge crack is estimated by iterative method. The fatigue life prediction method and calculation procedure of the impeller structure is summed up based on the fracture mechanics.