An Experimental and Numerical Investigation on Fatigue Life Cycle of Leaf Spring

Leaf spring is the key component of the vehicle suspension system that affects the mechanical behavior of vehicle vibration, stability, damping, and other aspects like comfort. However, depending upon the geography and road conditions, its fatigue life may vary. In Nepal, public vehicles operate mainly on paved roads and gravel roads under variable loading conditions. The road tested in this paper includes an urban road ranging 45km from Ratnapark to Sundarijal. The road consists of paved surfaces and gravel roads with varying degrees of slopes, potholes, and cracks. This paper discusses the fatigue life of a leaf spring in a public bus (TATA-709) operating on an urban road. Miner’s rule is used for the experimental analysis. Miner’s rule requires real-life data for the number of stress cycles. The data is obtained from the public bus using the data collection module. The number of repeated stress cycles was computed using the Rainflow cycle counting method and, the fatigue life is calculated implementing Miner’s rule. To validate the experimental results, fatigue simulation is carried out in ANSYS. The stress history data obtained from the experiment is fed into the fatigue model in ANSYS. The result shows that the number of cycles to failure obtained from ANSYS exceeds the number of cycles of failure obtained from Miner’s rule by 5%. This discrepancy indicates the need to consider further factors beyond this study, such as rusting, creep, and pre-stress, which considerably change the material properties and fatigue. This study sets a method to determine the fatigue life cycle of a leaf spring in various road and loading conditions both experimentally and numerically, to avoid potential damage due to failure of the suspension system in a public vehicle.