Stress Intensity Factors in a Rotating Impeller Containing Semi-Elliptical Surface Crack

Rotating compressors have been used for many years to compress gas in the oil and gas industries. Fatigue surface cracks at the stress concentration regions are the most common damages that cause the catastrophic failure of impellers. Stress analysis of surface cracks are needed for reliable prediction of their crack growth rates and fracture strengths. In this paper the problem of mixed mode fracture induced by a semi-elliptical surface crack lying at the stress concentration zone of a rotating impeller under general condition of loading is studied. Different values of the geometrical parameters which define the cracked configuration being considered. The problem of very rapid changes in the geometrical parameters in the vicinity of the crack front, which needs to incorporate very high mesh density, is solved by applying the submodeling technique in the analysis. Stress intensity factors in mixed mode condition are determined using three-dimensional finite element model. The calculated stress intensity factors are reasonable and could be used to predict the probable crack growth rates in fracture mechanics analysis.