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

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.</jats:p

Microstructure analysis on spring steels due to fatigue failure

Organized by School of Materials Engineering & Sustainable Engineering Research Cluster, 1st - 2nd December 2009 at Putra Brasmana Hotel, Kuala Perlis, Perlis.Fatigue on metal is one of the common phenomenons that people have been continuously exploring and trying to describe the whole process. This type of failure occur when component are subjected to cycle loading that is usually under the yield strength of the material itself. Leaf spring is one of the example for the component that dealing with cyclic loading. Sample of parabolic spring that fails from the fatigue test was study using optic and scanning electron microscope. From the analysis, there is some different or change in term of grain size but not very significant to fatigue properties. This paper objective is to study the microstructure behavior in term of size evolution between both areas and study the relation to the fatigue failure