Failure and fracture analysis of al-alloy wheel rim of a vehicle

Abstract

An Al-alloy wheel rim, showing a transverse and axial fracture was submitted for failure analysis investigation. A localized dent advocating the occurrence of intense plastic deformation was observed adjacent to the fracture area. In the frame of the present study, macro-and micro-fractographic analysis along with microstructural examination and mechanical testing were employed as the principal analytical methods for the investigation. Fractographic assessment indicated the presence of rough fracture surface topography, without signs of any subcritical or progressive cracking region, as suggestive evidence of fatigue. Conversely, the transgranular quasi-cleavage fracture together with minor shallow dimple terraces/tear ridges is indicative of low ductility overload fracture. Metallographic examination using SEM/EDS analysis revealed a typical as-cast structure with shrinkage cavities and intermetallic phases, pertaining to the Al-Fe-Si and Mg-Si constituents. No significant macro-defects were found that could be inculpated as the causative factors of the overload fracture of the wheel rim, rather than an impact incident that might have induced a high strain-rate loading crack propagation having resulted in the ultimate failure.