Investigation of the mechanical properties improvement on polymeric coated mono leaf springs

The leaf springs are used mainly for commercial vehicle and trucks suspensions and in one form consist of a stack of slightly curved narrow plates of equal width and varying length clamped together, with the shorter plates in the centre to form a semielliptical shape. The steel strips of a leaf spring are curved into an arc and attached at each end to the underside of a vehicle to help position and support the axle, and also to absorb shock. The leaf springs must absorb the dynamic loads, so their raw material is tough spring steel. In this study, shot penned leaf springs were coated with polymer material and mechanic properties were compared to electro coated leaf springs. On the real road conditions stones crash to leaf spring's surface. This stone chip effect were simulated with a test mechanism which was designed by using free fall principle and real stones were crashed to surfaces of leaf springs with the energy of average vehicle speed. After simulated stone chip test corrosion tests were applied to two specimens just their coating different. Corrosion on the surfaces of the leaf springs were observed. Then fatigue tests were applied to leaf springs. Difference between failure characteristics of the damaged leaf springs examined and fatigue lives were compared. Mechanical properties of polymer coated leaf spring were observed to be better than the electro coated leaf springs. Stone chip strength of polymer material provide the undamaged leaf spring surface after stone chip and prevent corrosion resistance. Effect of these mechanic improvements on fatigue life was examined with fatigue tests after accelerated corrosion tests on the damaged leaf springs. KEY WORDS: Leaf Spring, Polymeric Coating, Stone Chip, Corrosion, Fatigue test