Precise estimation of individual leaf camber and stepping in symmetrical 65Si7 leaf springs

Abstract

The term symmetrical multi-leaf spring is generally applied to springs of constant width, properly stepped leaves and each leaf of constant thickness and equal cantilever lengths. The main leaf is under the action of longitudinal and lateral forces during its operation, hence it is not desired that the maximum stress is induced in it. To reduce this stress, leaves with different unassembled cambers are assembled by pulling against each other and a common curvature is established. This causes stress concentration or set assembly stress in the assembled leaf springs. The assembly stress is subtractive from load stress in the master leaf, while it is additive to load stress in short leaves. It is possible to distribute the stress in a desirable manner among the leaves by a suitable combination of assembly stresses and stepping. The work presented in this article provides a design procedure for the number of leaves, stepping, individual leaf camber and no load assembly camber of leaf springs used in a light commercial vehicle. A proper combination of stepping and camber has been proposed by taking leaf spring design parameters into consideration, so that the stress in the leaves does not exceed maximum design stress. The leaf springs with the proposed parameters have been manufactured and tested on a full-scale leaf spring testing machine. The analytical stepping, no load assembly camber and individual leaf camber were compared with actual leaf spring for validation.