Failure analysis and optimization of coil spring fracture in MacPherson suspension system

During a vehicle accelerated corrosion test, a front coil spring in the MacPherson suspension system of an SUV exhibited fracture failure. The results indicated that the material composition, microstructure, and decarburization layer of the coil spring met the technical requirements; however, the tempering hardness was found to be excessively high. Fracture surface analysis revealed a small amount of intergranular cracking in the crack initiation zone, and the crack propagation zone exhibited ductile tearing characteristics, ultimately leading to fatigue fracture. Through force analysis, it was determined that the coil spring was subjected to lateral loads. Additionally, ABAQUS software simulations revealed that during wheel hop conditions, the coil spring end coil came into contact with the spring seat, leading to coating failure and the formation of surface fatigue defects. Based on these findings, an improvement plan was proposed, followed by failure reproduction and optimization validation in a test rig.