Failure Analysis And Finite Element Calculation Of Fuel Injection Pump Fork Assembly In Diesel Engine

Failure happened on two trucks during service.After inspection,it was found that the fork assembly used in diesel engine injection pump fractured.In this paper,two failed fork assembly were analysed to determine the failure modes,and fracture sequence of the components of assembly and the improvement suggested was made.The macro and micro fractures of failed fork assembly were observed by visually and SEM.The microstructure in various were observed by OPM and SEM.The chemical composition of materials of related components and micro-composition in various regions were determined,compared with the technical specification.Based on the finite element analysis software ABAQUS 6.12,the intermediate transition block was taken as the main research object.Furthermore,the loading mode of the intermediate transition block in the actual operating condition was studied.The main conclusions of the paper are as follows:(1)For the failed two forks,fracture occurred on the roots of convex platform.And the failure mode was multi-source high cycle fatigue fracture.The presence of rough machining marks on the root of the convex platform was responsible for the initiation of the fatigue crack.(2)For the two intermediate transition blocks,the fracture mainly initiated from the fillet root of the U shaped groove.The failure mode was also fatigue fracture.The presence of axial electric-spark marks on the fillet root of the U shaped groove and the presence of rough file marks on the chamfer of its side were mainly responsible for the initiation of fatigue crack.(3)The two-dimensional static analysis of the intermediate transition block showed that the fillet root of the U shaped groove was the stress concentration area.The stress concentration at the root of the U shaped groove and the poor machining surface mainly contributed to the crack initiation.(4)In the two-dimensional static analysis of the intermediate transition block,the angle between the crack initiation direction and the circumferential direction under different loading modes was measured under different loading modes.The loading modes of intermediate transition block in actual operating condition were studied.