The analysis of the failure of leaf spring used as the rear suspension system in 110 PS diesel trucks

Abstract

Leaf springs are designed to dampen the vibrations caused by different loadings such as lateral loads, shock loads, and torsion. The important role of this component in a vehicle makes its failure cause serious accidents. Therefore, this study aimed to determine the cause of leaf spring failure in the 110 PS dump truck vehicle suspension system. An experimental approach was adopted and this involved the visual and fractographic observation of the fracture surface, hardness test, chemical composition test, microstructure evaluation, and analysis to determine the magnitude of the stress intensity factor. The results of observations showed the presence of a chevron pattern indicating an initial crack in the leaf spring followed by a beach mark pattern which is evidence of repeated loading. Moreover, a smooth flat part in the fracture surface was discovered to be the final fracture zone while the values obtained from the hardness test were found to be more than the standard required. This spring fracture was also observed to have been caused by the fact that the truck carried a load which exceeds its carrying capacity. The stress intensity factor analysis produced KI values which are very close to the fracture toughness KIC value of the spring material and this caused the crack propagation to fracture. The failure in the leaf spring was caused by an initial defect observed on the inside of the hole in the spring. Moreover, the dynamic loads carried by the spring acting as a suppression system caused the initial crack followed by the crack propagation and the final fracture.