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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.

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Heavy-duty commercial vehicles play a significant role in commodity logistics. For each of these vehicles, the suspension is the most essential system to support the load and road shock. Bogie type suspension system is employed to safeguard the vehicle from road shock. The bogie bracket is a juncture between the chassis and the axle in the suspension system. The bogie bracket has been identified as a critical part of the suspension system. In the present study, bogie bracket base design and modelling was performed using computer-aided engineering (CAE). The strength of the bogie was tested to identify weaker sections. Design modifications were performed to improve the strength on identified critical sections through reinforcement techniques. A road load data acquisition (RLDA) test was conducted under different road conditions to validate CAE results. Five different rough-road road surfaces were chosen for RLDA testing. Using strain gauges, strain data were acquired during the test. Corresponding stress values were obtained and maximum stress was found in all driving conditions. For the base design bogie bracket, under RLDA test, crack initiation and crack propagation were identified under vertical loads. A reinforced bogie bracket was designed and found to have a higher strength and longer expected life than that of the base design.