Unconventional Truck Chassis Design with Multi-Functional Cross Members

An unconventional conceptual design of truck chassis with multi-functional cross-members is proposed, and an optimization framework is developed to optimize its structure to minimize mass while satisfying stiffness and modal frequency constraints. The side rails are C-sectional channels of variable height and were divided into six sections, each with different thickness distribution for the flanges and the web. The gearbox cross-member and the intermediate cross-members are compressed-air cylinders, and hence they act as multi-functional components. The dimensions and thickness of the side rails and the air-tank cross members are defined by a set of parameters which are considered as design variables in the optimization problem. The structure consists of three additional fixed cross-members which are modeled using beam elements. The limits of the design variables are decided while considering manufacturing limits. Additional geometric constraints are imposed considering the front and rear axle locations. The baseline model is verified by comparing the values of torsional stiffness, vertical bending stiffness and the frequencies corresponding to lateral bending mode, torsional bending mode and vertical bending mode with those of the high-fidelity model of comparable dimensions. A novel algorithm using Mode Assurance Criteria (MAC), is developed to find the appropriate vertical bending frequency. The design variables are optimized considering constraints on vertical bending frequency, torsional stiffness, and vertical bending stiffnesses using the Particle Swarm Optimization (PSO), which is implemented using parallel processing. The optimized design has 10% less mass than the baseline model while having almost equal stiffness.