Design Development and Performance Analysis of Leaf Spring Testing Set up in Elastic Domain

Leaf spring is the simplest type of suspension spring commonly used in wheeled vehicles and its main cause of failure is large bending under load. Leaf spring is generally designed by modeling it either as curved cantilever beam with tip concentrated load or curved beam under three point bending. In spite of the widespread theoretical static analysis of leaf spring, there is lack of experimental fidelity in the ensuing models. Moreover, there is insufficiency in modeling the roller supports at eye ends and in addition, asymmetry in master leaf geometry and presence of drill hole in master leaf have not been considered properly. This paper presents design development and performance analysis of two different leaf spring testing rigs. The design considerations, detail descriptions of the components along with their manufacturing details are furnished here. The first set-up is a general purpose set-up for clamping structures, which models leaf spring as curved cantilever beam under tip concentrated load by considering only its one half. Experiment is carried out in this set-up to obtain deflection profiles of master leaf spring using image processing technique. Comparisons with theoretical results identify several insufficiencies in the present experimental model such as unknown clamping force, non-consideration of asymmetry in master leaf geometry and inappropriate modeling of support arrangement at eye ends. To overcome such insufficiencies, the second set-up is designed which simulates three point bending test. This set-up introduces roller supports at eye ends and considers asymmetry in the master leaf geometry. In both the cases, deflection profile is obtained using image processing technique and in the second set-up, strain gauge technique is adopted for strain measurement.