Static and Modal Analysis of a Leaf Spring Assembly Using Contact Nonlinear 3D Finite Element Approach

Suspension system in an automobile determines the riding comfort of passengers and the amount of damage to the vehicle. The main function of a leaf spring assembly as suspension element is not only to support vertical load but also to isolate road induced vibrations. This makes the static analysis and modal analysis of a leaf spring is very essential to predict the strength and vibration behavior. Stacking seven thin metal leaves of different lengths, the longer leaves on top of the shorter ones and banding them together with the help of one center bolt, two U clamps and four rebound clips forms a leaf spring assembly. This assembly is connected with chassis frame by shackle. Hence, the behavior of leaf spring is highly complicated due to its clamping effects and inter-leaf contact etc. To incorporate the assembly effect, contact nonlinear analysis is performed in the three-dimensional model of leaf spring. The static analysis results are compared with experimental results. A fairly good agreement between the experimental results and the finite element analysis results are observed. A modal analysis is carried out with the same three-dimensional model leaf spring. It is founded out from literature survey that, for the suspension system of the passenger car automobiles the excitation frequencies are ranging from 1Hz to 80 Hz due to road irregularities, damping etc. Hence, the leaf spring model is analyzed only up to 20 mode shapes for amplitudes and stress values. Critical modes and level of free vibration details are identified to avoid resonance under operating conditions.