Microstructural Behaviour Study and FEA-Based Fatigue Simulation on Parabolic Leaf Spring

Abstract

It is compulsory to have a good fatigue life to a component that is heavily subjected to cyclic loading. One of the good examples is parabolic spring, which is one of the components in suspension system for large vehicles. It serves to absorb, store and release back the damping energy due to road irregularity, bump and holes. These activities involve a lot of camber deflection that caused by the tension and compression loads. In reality, the loading that subjected to parabolic spring is variable amplitude loading, but most of the manufacturer used constant amplitude (CA) loading for the fatigue test. The objective of this paper is to relate the simulation result with the microstructure behaviour of the leaf spring that failed due to fatigue. A full scale fatigue test was carried out until that parabolic spring meet failure. In order to investigate the fatigue life, CA signal was generated based on an actual fatigue test on the parabolic spring, and it was then analysed using the FEA-based fatigue simulation. A microstructure study was then performed for both fracture and non-fracture area. From the FEA-based simulation, it gave the prediction on damage that occurred at the critical area and also the prediction on the lowest cycle with respect to the FEA model. In the actual fatigue test, the failure was occurred at the centre part of the spring, which is at bolt join of assembly hole. The microstructure analysis showed that the grain at the fracture area indicated some different from the non-fracture area in term of size, phase and precipitation of carbon.