This paper investigated a failure in a ventilated disc brake in an automobile. The failed\nbrake disc had been in service for approximately 10 years. The observed failure was in the form\nof radial cracks that appeared to have initiated at the outer edge of the disc brake. The cracks\nwere rather straight with no branching. Optical microscope, scanning electron microscope (SEM),\nand energy dispersive X-ray spectroscopy (EDS) were used to study the microstructure of the failed\ndisc. Vickers microhardness test was also used to evaluate the hardness of the samples. Results\nshowed that the root cause of crack formation, in this case, was related to the excessive wear in the\nbrake disc. Different wear mechanisms, namely abrasive and adhesive wear, were recognized in the\nfailed specimen. Moreover, the worn surface in some areas was covered with fine oxide particles.\nThese particles appeared to have a significant contribution toward abrasion. To further understand\nthe wear mechanisms, pin-on-disc experiments were also conducted on the samples. Results of\nthe pin-on-disc experiments were compared and correlated to the results obtained from the failed\nbrake disc.
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