Investigation of service failures in automobile shock absorbers

Several premature service failures of car shock-absorbers, supplied by a same manufacturer, had taken place. Fracture had occurred at the head of the damping device through a welded zone at the piston-rod/ring junction. Failure analysis (mechanical tests, metallographic and fractographic examinations) has been carried out. It has been found that undesirable porosity, cracks, inclusions and low-strength microstructures developed during welding. Failure, nevertheless, is mainly attributed to a poor alignment of the junction parts during the welding operation.