Failure Analysis on High Pressure Fuel Pipes Used in Truck Diesel Engine

The high pressure fuel pipes used in truck diesel engine cracked in service. The crack morphology and fracture surfaces of cracked fuel-pipes were observed by stereomicroscope and scanning electron microscope. The results indicate that the failure mode of all the fuel-pipe was fatigue fracture. The crack origin was originated from the micro-cutting marks on the internal surface due to grit-blasting for cleaning internal hole. The crack propagated from the internal surface toward the external surface under the circumferential tensile stress due to the operating oil-pressure in the internal hole to lead to fatigue.