Abstract:

A topology optimization was made for the transverse beams on floor and the reinforcement beams
(diagonal bracings etc.) to reduce chassis mass and to improve reinforcement beams layout of an integral bus
chassis. The zone between the front and rear axles was chosen to construct the topology design space. A
topology optimization formulation was established with the objective being to minimize bus body mass and the
constraint being that bus body torsional stiffness is no less than that of original design. Genetic algorithm was
employed to solve the problem to achiev an optimal topology. An improved design was attained based on the
topology optimization result and the assembly requirement. The number of reinforcement beams in the design
space is reduced from 9 to 3, the bus body torsional stiffness is increased by 150 Nm/(°), and the bus body
mass is reduced by 20.8 kg comparing with the original design. The material utilization, the ratio between the
increments of bus body torsional stiffness to the structures mass in the design space, is increased by 1.5 times.

Key words:  integral bus, chassis, lightweight, topology optimization, genetic algorithm