Development of simulation methodology to evaluate Leaf Spring strength and predict the Leaf Interface stresses and correlating with test

Leaf Springs are commonly used as a suspension in heavy commercial vehicles for higher load carrying capacity. The leaf springs connect the vehicle body with road profile through the axle & tire assembly. It provides the relative motion between the vehicle body and road profile to improve the ride & handling performance. The leaf springs are designed to provide linear stiffness and uniform strength characteristics throughout its travel. Leaf springs are generally subjected to dynamic loads which are induced due to different road profiles & driving patterns. Leaf spring design should be robust as any failure in leaf springs will put vehicle safety at risk and cost the vehicle manufacturer their reputation. The design of a leaf spring based on conventional methods predicts the higher stress levels at the leaf spring center clamp location and stress levels gradually reduce from the center to free ends of the leaf spring. In RWUP conditions, the failures of leaf spring can occur at the leaf interfaces (i.e. where the succeeding leaf ends) in addition to center clamp locations. The aim of this paper is to capture and demonstrate the potential failure at leaf interfaces which is not predicted through conventional methodology, in addition to leaf center. The experimental strains measured on leaf spring using strain gauges in vehicle level testing are correlating with the strains predicted by the proposed simulation methodology. The correlation is demonstrated on the front leaf spring of pickup vehicle. An investigation into new simulation methodology is incorporated to study the base design and further the influence of design parameters, nipping, leaf travel, shot peening and stress peening processes were explored to improve the design. Based on these studies the new design is proposed that incorporates stepping, stress peening and diamond cut design which improves the life considerably.