Factory fracturing is characterized by high pressure, large discharge capacity and long-time service for shale gas well, then unite of fracturing pump operates under more severe condition with complex load and corrosion. Failure analysis was performed for crankshaft via theoretical calculation, finite element modelling and fractographic observation in fracturing pump with model QWS-2800. The results indicated that fatigue fracture was the dominant failure mechanism, with evidence of beach and striation marks and multiple fatigue cracks. The fracture plane had nearly 45 degrees inclination with respect to the shaft axis. The main cause of insufficient fatigue strength was due to absence of surface hardening treatment. Fillet radius was a main factor for fatigue crack initiation, the fatigue crack mostly located in the thread root of radial oil hole. Finite element analysis results indicated that the stress increased remarkably as fillet radius decreased. Then stress concentration became much higher with the transition of thread root from smooth to sharp fillet. It provides some suggestions to prevent the crankshaft rupture in terms of fatigue strength and thread structure.
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