Methodology to Analyze the Suspension Influence on Propeller Shaft Efforts

With the constant evolution of vehicle systems becomes increasingly challenging the Components project. The demand for mass and cost optimization in a challenging project schedule scenario generates a great challenge to the engineering teams, who look for design and development methods more assertive. In order to reduce the risk of failure, testing time and design cost, simulation tools are being increasingly used. A major challenge in the component project for trucks and buses is the knowledge of the real loads that the components are subjected. In the case of propeller shaft bearings several factors should influence the magnitude of the efforts. The biggest influent factors that has been studied and discussed widely for many years are the torque and joints angles. The “SAE Universal joint and drive shaft design manual” depicts masterfully some formulations to determine the bearing efforts considering effects of geometry and torque, however, with the practical experience, we are faced in some specific situations, with components lifetime lower than expected and even with components plastically deformed demonstrating that the real efforts were higher than the initial design consideration. In vehicle tests we observed that the suspension presents high deformation on abrupt maneuver and that the effect of modifying the geometry should be further studied. The suspension movement occurs mainly for 2 reasons; the torque from engine that causes wind up on the springs and the load transfer that affects the spring deflection. To study the rear suspension geometry changes influence in propeller shaft bearing efforts a multibody model was created allowing the comparison of a vehicle with flexible suspension with a pseudo vehicle with rigid suspension. In this way we can through this study to identify the contribution of the suspension flexibility on propeller shaft bearings efforts getting more suitable design criteria for these components.