Evolution of 52CrMoV4 from 51CrV4 material to withstand field severity of parabolic leaf spring suspension in heavy-duty commercial vehicles

Abstract

This investigative study is mainly focused on improving the fatigue life of the leaf spring through the following protocols. In protocol 1, a parabolic leaf spring is manufactured with 51CrV4 material through normal production processes, which results in low residual compressive stress and high decarburization. The resulting proto sample does not support severe field application. This issue can be resolved by optimizing the heat treatment and the shot peening process. The proto part was prepared and tested under rough road conditions, and the vehicle withstood field severity up to 10% higher than the design load. However, under highly severe field operation, the severity was 30% higher than the design load. Hence, the above process improvements could not resolve the failures of the 51CrV4 material. Hence, an alternate material is identified, 52CrMoV4, and investigated. In protocol 2, the spring proto part is manufactured directly through an optimized process. The residual compressive stress, decarburization, and mechanical properties are obtained at desired levels. The proto part was tested under rough road conditions; the suspension system withstood a field severity of 30%. The vehicle was then tested on the test track and covered 335 000 km of off-road distance, with all durability requirements met.