ABSTRACT
In this study the effect of cyclic plastic deformation on the mechanical properties of a
light duty grade of spring steel DIN 50Cr3, commonly used in leaf spring was
investigated. This steel has a chemical composition of 0.25% C, 0.8% Cr, 0.79% Mn,
and 0.2% Si. Primarily, standard tensile specimens of this steel were cut and
subjected to a quenching and tempering heat treatments. Austenitization was carried
out at 870oC for 1h followed by quenching in oil and then tempering was applied at
450oC for 1h. Subsequently, Different pre-plastic deformation strains of 1%, 2%, and
2.5% were applied followed by various number of tensile stress cycles from zero to a
maximum stress of 9%, 12.5%, and 16.5% over the offset yield stress of the
quenched and tempering specimens. These plastic strains and stress cycles can
simulate the possible over loading of the vehicle. By increasing the number of cycles
under a constant amplitude for a given fixed pre-plastic strains, the ultimate and
offset yield strength of the spring material were sensibly increased while ductility was
drastically decreased.