A Microstructural and Fractographic Study on the Failure of a Drive Shaft

The automotive industry is one of the most dynamic and competitive segments of the international economy and it has invested considerable resources into the research and development of new components and the improvement of existent pieces. Nonetheless, failures continue to occur, often because of defects in a component. Failure analysis uses several techniques to investigate causes of the defect which led to the failure of a component, equipment, or structure. Usually, these causes are related to the use of inadequate materials, the presence of defects which appear during fabrication or design errors, or improper assembly, maintenance and use. Knowledge about these causes and the correction of such anomalies allow the improvement of the performance of components regarding both efficiency and safety. In this study, the results of the failure analysis of the drive bar of a police car are presented and light optical microscopy and scanning electron microscopy (SEM) results are used to show that the presence of an already existent defect and an unfavorable microstructure led to the occurrence of brittle fracture which caused the premature and catastrophic failure of this component.