Effect of surface decarburisation, scragging stress and individual leaf camber on fatigue life of 65Si7 leaf springs

Abstract

The production process of high strength leaf springs, comprises of shearing, punching, heat treatment, hot cambering, shot peening, scraging and subsequently testing for load rate and durability. The processing of the raw material plays a vital role in achieving the required fatigue life. The objective of the present work is to determine the effects of material processing and design parameter on the fatigue life of the leaf springs. The material processing parameters considered are surface decarburisation and scragging stress while the design parameter considered is individual leaf camber. A light commercial vehicle (LCV) leaf spring is taken into consideration for this work. The partial and complete surface decarburisation during the rolling is determined and its effect on the fatigue life is predicted. The effect of the scragging stress on the fatigue life is also determined. An ideal range of scragging stress is proposed for fatigue life enhancement. A suitable individual leaf camber is proposed for the individual leaves. The leaf springs with proposed camber are manufactured, assembled and tested on a full scale leaf spring testing machines. The effect of the assembly stresses due to individual leaf camber on the fatigue life is also determined.