MULTI-MATERIAL DESIGN OPTIMIZATION OF A BUS BODY STRUCTURE

Abstract

In the recent years the safety and eco-friendliness have gained much of attention of the automotive stakeholders. These two characteristics are especially important in the case of mass transportation vehicles, such as buses or coaches, which are in continues use for long periods of time, covering significant distances. In such situations, the economical aspects play major role for the transportation companies which try to minimize operational costs of their fleet, by choosing vehicles with reduced fuel consumption. In order to obtain improvements in all the mentioned areas and hence to strengthen their position on the market, bus manufacturers have recently turned their attention to multimaterial design strategies. Structures built in that manner consist not only of regular steel parts, but contain also a mix of components made from various lightweight materials like aluminum alloys or composites, which allow for significant reduction in vehicle curb weight. However, due to the differences in mechanical characteristics which are especially evident in the case of laminates, the material substitution is not a straightforward task. In order to find the material distribution pattern that meets all the requirements, a great number of prototypic numerical models must be prepared and tested. To ease the search for the final solution, optimization techniques can be applied into the design process, allowing for automatic design modifications and assessment of the obtained results. The paper presents an attempt of enhancing the operational characteristics of a bus body structure with simultaneous reduction in the structural weight. In order to find the optimal component configuration, a multimaterial optimization was employed and supplemented by sensitivity and robustness analyses. Such a technique helps to discriminate the over-optimized solutions that are often pointed out as the most desirable by the optimization algorithms which neglect the uncertainties of the analysed system.