Weight reduction of heavy-duty truck components through hollow geometry and intensive quenching

Increasing environmental awareness has put pressure on heavy duty truck manufacturers to improve the fuel economy and reduce the emissions of their vehicles. Light weighting efforts are a useful tool in meeting these goals. As a demonstration of how light weighting practices can be applied to the power trains of heavy duty vehicles, this paper focuses on reducing the weight of the rear axle shaft. Two methods are focused on, i) hollow shaft geometry and ii) intensive quenching, as possible avenues to shed mass from the shaft. Load mapping is used to establish a finite element model which can be used to evaluate the light weight designs and techniques proposed in the paper. It is discovered that weight savings of around 26% can be achieved by changing the traditionally solid axle shaft into a hollow shaft. The intensive quenching process is shown to be superior to the oil quenching process in regards to both residual stresses and strength, allowing for material removal accounting for 3% of the shaft weight. Additionally, the compressive residual stresses created on the surface of the part during the intensive quenching process may also serve to slow crack initiation and increase fatigue life. Further optimization of the intensive quenching process may provide additional weight reduction opportunities.