Failure Analysis of an Automotive Bushing

The cause of a longitudinal fracture of an automotive bushing during the assembly process is presented in this study. On the basis of macroscopic inspection, scanning electron microscopy, energy-dispersive spectroscopy, microstructural examination, chemical analysis and hardness measurements, cleavage fracture was determined by the dominant fracture mode, and the fracture near the outer surface of the bushing was covered by impurities which is similar to the composition of the coating. Therefore, it is possible to infer that the crack existed before installation. In addition, the detailed metallurgical analysis demonstrates decarburization at the fracture surface due to a folding defect. In the process of assembly of bushing, the stress concentration and surface defect promoted the old crack propagation, finally, leading to the fracture of the bushing.