The failure analysis of bike brake lever: Observation on crack propagation and stress analysis

Abstract

A fractured bike brake lever of aluminum alloy was investigated using the observation on the crack propagation and the stress analysis. Observation on the crack propagation done by microscopy photo images and scanning electron microscope (SEM). The hardness measurement on the cross-section of the bike brake lever was done to determine the material hardness distribution. The stress analysis results were used to show the possibility that the initiation of cracks occurs at critical stress points. According to the visual observations, the area suspected to be the beginning of the appearance of cracks is the edge of the component fracture surface. There are few grain groups were pulled out in different directions. Different bifurcation direction occurs in the grain boundary, thus forms intergranular cracks propagation. The hardness test results show that the edge was harder than the middle. The bike brake lever that has high hardness is the cause of crack initiation due to overload and impact loads. Therefore, the suspected cause of the broken brake bike lever comes from the edge that has a higher hardness value than the middle of the specimen. The results of the simulation show three critical points correspond to the bike brake lever failure. Three critical points virtually create a fracture line that is probably the fracture pattern of the bike brake lever. The increased in the strength of the bike brake lever can be done by the increasing of its thickness. Increasing the thickness of the bike brake lever can increase the cross-sectional area of the cable pin pulling pivot. The increase in thickness causes a decrease in maximum VonMises stress and an increase in maximum load.