Lightweight steel Leaf Springs with improved durability and reliability

ended

EURO-VI directive for emission reduction forces to cut weight of trucks, vans and other LCV and HCV. In particular, this means to reduce weight of suspension leaf springs. Despite the effort made up to date, further weight reductions must be achieved. Leaf springs currently are made with CrV steel grades, that are hot rolled, quenched and tempered and stresspeened. To make feasible a leaf spring downweighting and cope with higher bending stresses, two approaches are possible: the optimization of residual stresses due to complex stresspeening process and the development of ultra high strength steels. The interactions and synergies bewteen innovative complex stresspeening processes and novel ultra high strength leaf spring steels will be studied at experimental and industrial scale, with the aim of lightening these components, guaranteeing an outstanding fatigue performance. The aim of LEAFSLIM project is the weight reduction of the leaf springs for suspensions of light and heavy duty commercial vehicles through: ─ Development of novel steel grades for lightweight leaf spring applications ─ Optimization of the Residual Stress profile through innovative stresspeening processes to achieve an enhanced profile of residual stresses, smoother surface roughness and relaxation resistance ─ Improvement of fatigue performance of the final components through a decrease in crack propagation rate within the residual stress field ─ Development of a Woodvine-analysis including the transient physical mechanisms of the peening processes derived from the residual stress profile and the microstructure of the new steel in order to predict fatigue lifetime and fatigue damage