Design optimization of heavy motor vehicle chassis

Abstract

A vehicle chassis is one of the most vital components of an automobile. It supports various components like the vehicle body, engine, and suspension and transmission system. The purpose of heavy-duty motor vehicles (HMV) is to carry large loads, and this is often in harsh conditions. Therefore, the chassis design should withstand undesired static and dynamic loads experienced by the vehicle when in operation. Identifying and improving the properties of the chassis that affect the field performance of these vehicles is the key challenge faced by HMV designers. In this work, the chassis considered for improvement is the steel (St52E) TATA 1612 truck. The main measures identified for a compliant chassis are; satisfactory equivalent stresses, deformation, strain energy, safety factor and weight reduction. The chassis properties identified for improvement are the geometry (dimensions and cross-sections) and chassis material. In terms of geometry, different chassis member cross-sections (square, C, I and T) were studied under static loading. The above geometry studies are then adopted on a number of proposed metal matrix composite (MMC) materials. These are Graphite Al GA 7-230, P100/6061 and Al 6092/SiC/17.5P. In order to systematically improve these chassis variable properties, finite element model (FEM), modal analysis and Taguchi response surface methods (RSM) are used. Utilizing Taguchi design of experiments (DOE), the optimization design points are generated. The methods used are the central composite design (CCD), optimal space fill (OSF), Behnken-Box (B-B), Sparse Grid Initialization (SGI) and the Latin Hypercube (LH) design schemes. The I and T cross sections are found not to be compliant with acceptable industry requirements for application on HMV chassis. The Graphite Al GA 7-230 material, using the square profile, shows the lowest deformation of 78.33 mm and Al 6092/SiC/17.5p shows a maximum deformation of 694.83 mm under static loading. The optimization results show that the percentage of weight reduction obtained is 5.37% for the St52E material using the CCD scheme. By using P100/6061 Al and Al 6092/SiC/17.5P materials, the chassis weight reduction is 68.15% and 64.3% lower respectively over the standard St52E.