Effect of End Rubber Gasket on the Performance of Parabolic Leaf Spring

Leaf springs play an important role in the handling stability and ride comfort of vehicle. End rubber gaskets are widely used to reduce the friction between leaves, but they also have considerable effect on the stiffness of the suspension assembly. The ride comfort may deteriorate with the stiffness of leaf spring changes. In this paper the influence of the end rubber gasket on the static stiffness performance of a parabolic leaf spring is studied. A finite element model of the leaf spring is developed and verified against the static stiffness test. Effects of the end rubber gasket parameters on the static stiffness of the leaf spring are analyzed based on an orthogonal experiment. The sensitivities of the five parameters are identified including the width, the length, the end thickness, the tail thickness and the distance to the end of the middle leaf. It is found that the contributions can be ranked in descending order as the tail thickness, the end thickness, the distance from end rubber gasket to the end of Leaf 2, and the width and length. The first two factors are considered of significant effects on the leaf spring stiffness. According to single-factor analysis, it is found that under the same load, as the tail thickness and the end thickness increase, the maximum deformation of the rubber gasket decreases, the stiffness of the rubber gasket increases, and the stiffness of the leaf spring increases, which provides a reference for the forward design of the end rubber gasket and the stiffness matching of leaf springs.

Experimental and numerical analysis of the static strength and fatigue life reliability of parabolic leaf springs in heavy commercial trucks

The objective of this study is to perform experimental and numerical analysis of the static strength and fatigue life reliability of parabolic leaf springs in heavy commercial trucks. To achieve this objective, stress and displacements under static loading were analytically calculated. A computer-aided design model of a parabolic leaf spring was created. The stress and displacements were calculated by the finite element method. The spring was modelled and analysed using CATIA Part Design and ANSYS Workbench. The stress and displacement distributions on a three-layer parabolic leaf spring were obtained. The high-strength 51CrV4 spring steel was used as sample parabolic leaf springs material, and heat treatments and shoot peening were applied to increase the material strength. Sample parabolic leaf springs were tested to obtain stress and displacement under static loading conditions. By comparing three methods, namely, the static analytical method, static finite elements method and static experimental method, it is observed that results of three methods are close to each other and all three methods are reliable for the design stage of the leaf spring. Similarly, sample parabolic leaf springs were tested to evaluate the fatigue life under working conditions. The reliability analysis of the obtained fatigue life test value was carried out. It was shown that both analytical model and finite element analysis are reliable methods for the evaluation of static strength and fatigue life behaviour in parabolic leaf springs. In addition, it is determined by a reliability analysis based on rig test results of nine springs that the spring achieves its life cycle of 100,000 cycles with a 99% probability rate without breaking. Furthermore, the calculated fatigue life is 2.98% greater than experimentally obtained fatigue life mean and the leaf spring can be used safely and reliably during the service period in heavy trucks.

Design Optimization of an Automotive Component in Product Development

This paper will briefly explain the engineer’s approach to optimize the conservative design of parabolic Leaf Spring in various steps. The Hybrid Design methodology and technique is employed for Size. Shape and weight Optimization by means of Parametric Modeling and Optimization-Simulated annealing algorithm. Various designs have been created, analyzed and its Maximum deflection and stress is compared with the material’s yield strength.

Evolution of 52CrMoV4 from 51CrV4 material to withstand field severity of parabolic leaf spring suspension in heavy-duty commercial vehicles

This investigative study is mainly focused on improving the fatigue life of the leaf spring through the following protocols. In protocol 1, a parabolic leaf spring is manufactured with 51CrV4 material through normal production processes, which results in low residual compressive stress and high decarburization. The resulting proto sample does not support severe field application. This issue can be resolved by optimizing the heat treatment and the shot peening process. The proto part was prepared and tested under rough road conditions, and the vehicle withstood field severity up to 10% higher than the design load. However, under highly severe field operation, the severity was 30% higher than the design load. Hence, the above process improvements could not resolve the failures of the 51CrV4 material. Hence, an alternate material is identified, 52CrMoV4, and investigated. In protocol 2, the spring proto part is manufactured directly through an optimized process. The residual compressive stress, decarburization, and mechanical properties are obtained at desired levels. The proto part was tested under rough road conditions; the suspension system withstood a field severity of 30%. The vehicle was then tested on the test track and covered 335 000 km of off-road distance, with all durability requirements met.