Failure Analysis of Leaf Spring used in Electric 3 Wheelers

The premature failure of leaf springs in commercial three-wheeler load carrier vehicles is a common occurrence that necessitates scrutiny during the design and development phase. By conducting thorough analysis at this stage, steps are taken to prevent such failures from happening in the future, thereby avoiding potential issues for customers during vehicle usage. When leaf spring fails in a three-wheeler, it can lead to a range of adverse effects. These include instability, difficulty in controlling the vehicle, reduced capacity to bear loads, uneven tire wear, increased vibrations, and the risk of a complete suspension system breakdown. Such consequences may result in the vehicle tilting, a heightened risk of accidents, and potential legal ramifications. To mitigate these risks, it is crucial to engineer a leaf spring suspension system that minimizes the likelihood of failures. By prioritizing reliability and safety in the design process, manufacturers can ensure the well-being of both the vehicle occupants and other road users. The main objective of this paper is to conduct a thorough analysis on the failure of one such developed which failed during a proto sample development phase during system level testing in a test rig. All the aspects of the design and development of the leaf spring were thoroughly reinvestigated. These include reworking on the design load calculations and verifying the maximum spring displacement for 2 g+ load conditions. Calculations were done to verify the stress on the leaf spring for max load conditions, considering GVW load as 1 g load. Finite element analysis was reworked to correlate the spring stress and deflection. Material engineering analysis was carried out subsequently to understand the nature of failure of the spring. Microstructural analysis with material specification is performed on fractured leaf springs mainly to understand the chemical composition. The failed part was subjected to a fractography study and performed hardness testing. Objective of the fractography study is to find out whether fracture is due to cyclic load or fatigue load and the propagation of the fracture growth. Based on the analysis outcome of the SEM study of the failed sample, learnings were applied to develop the new spring sample. Keywords: failure analysis, leaf spring, electric 3-wheelers, wheel travel, design calculation study, microstructural analysis, fractographic