Fracture failure analysis of metal materials by visual inspection and destructive testing

Abstract

A methodology is presented to perform fault analysis in metal materials that have failed due to fracture. The proposed method was applied to the study of a fracture presented in the jaw supporting the test pieces in a universal machine used for mechanical tests on materials. The analysis was structured in two stages, initially a visual inspection of the failed element, followed by a series of destructive tests to identify the characteristics of the material and the occurrence of the failure. Visual inspection identified the morphology of the material in the fault zone with gloss and with a characteristic cleavage fracture shape corresponding to a fragile and brittle material. With arc and spark spectrometry the composition of the material was identified, Metallography showed the formation of martensite typical of medium-carbon steels subjected to thermal hardening and scanning electron microscopy identified the precipitation of carbides at the grain boundary, as well as the presence of gaps and other metallic and non-metallic inclusions in the microstructure. The proposed methodology allowed to characterize the fault and propose an appropriate solution by identifying possible hidden faults solving the root of the problem.