Research on fatigue crack propagation process of fracturing pumphead

•Whole fatigue crack propagation process of pumphead is calculated.•In high/low stress zone of pumphead, KI increases/decreases with crack length.•A wave peak appears in the a-KI curve around the step structure. Fracturing pumpheads are a key and crucial component in fracturing technology. Fatigue crack failure greatly decreases the pumphead working life and operational efficiency. This paper describes an analytical model for a five-cylinder fracturing pumphead using the submodel method with the re-meshing technique to analyze its fatigue crack propagation process. Changes in the crack face, a-KI curve (crack length a and stress intensity factor KI), and a-N curve (number of fatigue loading cycles N) during crack propagation are considered. The results show that the crack failure of the fracturing pumphead results primarily from mode-I cracks. During crack propagation, the curvature of the crack front gradually decreases due to the higher stress intensity factor KI at the pressured inner surfaces of the pumphead. The stress distribution on the pumphead greatly influences the change law for the a-KI curve. When the crack tip localizes in the high stress zone, KI increases with the crack length a; when the crack tip localizes in the low stress zone, KI decreases with the crack length a. The step structure of the pumphead also influences changes to the a-KI curve. Around the step structure, a wave peak appears in the a-KI curve, but the influence is localised and its effect on the a-N curve is not significant.