Materials selection criteria for the weight reduction of high performance sports car

For high-performance luxury cars, the first element of competitiveness isgiven by the dynamic performances. Thus, weight reduction is becoming increasinglyimportant, also in the framework of the introduction of more andmore restrictive regulations on emissions. Designers are currently focusingon maximizing the power/weight ratio, and the proper material selectionbecomes mandatory. This paper describes the weight reduction achievable onthe suspension system of a Lamborghini Murcielago, showing that the useof high strength low alloy steels as well as titanium and aluminum alloysallows to reduce weight of selected components of more than 30%.Three different components of the suspension system have been analyzed:the front lower arm (fig. 1), the front suspension spring (Table II) and theanti-roll bar (fig. 5). According to the method proposed by M.F. Ashby [2],the design requirements have been translated into a series of constraints,objectives and free variables, leading to the definition of material indexes(equations 1-8) to be used to rank the materials in order to identify the mostsuitable ones. Ranking was accomplished using the CES (Cambridge EngineeringSelector, Granta-design) software, which allows to create selectioncharts like the ones shown in Fig. 2, 3, 4, 6. Those diagrams help the designerto select graphically the candidate materials for the application, which, forthe studied cases, resulted to be:- Low alloy steels or aluminum alloys (Table II) for the front lower arm- Titanium or spring steel(fig. 1), for the front suspension spring- Aluminum alloy for the anti-roll barDimensioning of the components on the basis of the selected materials ispresented as well, demonstrating that a proper materials selection procedureallows to significantly decrease the weight of the studied components withrespect to the current solutions.