Abstract: Failure analysis of the fractured front stabilizer bar of a certain vehicle in strength endurance road test was carried out by using direct reading spectrometer, hardness tester, scanning electron microscope and metallographic microscope. The results show that chemical composition and Rockwell hardness of the front stabilizer bar can meet the requirement of material standard and part drawing. The fracture failure mode is fatigue fracture. Connection zone between the stabilizer bar and the stop ring, hard and brittle secondary quenching martensite and low hardness secondary tempered troostite exist in the crack source because of the heat input of the welding process in installation of the stop ring. Fatigue fracture occurs in the area of the test and extends till instantaneous overload fracture occurs. Failure phenomenon reproduced through rapid fatigue bench test. Such kind fracture failure can be avoided by controlling the welding parameters of the stop ring to make the microstructure of the stabilizer bar not be influenced.

Key words: front stabilizer bar, fatigue rupture, welding of stop ring, secondary quenching martensite, rapid fatigue bench test