With growing public concern regarding the rising price of fossil fuel and the greenhouse gas emissions, the automotive industry is faced with the increasing challenge of developing more fuel-efficient vehicles. Savings in weight using lightweight materials such as aluminum can lead to increased fuel economy and reduction in pollution.

Aluminum has superior corrosion-resistance and recyclability compared to mild or high strength steel. Usage of aluminum would, however, undoubtedly have a negative impact on cost. But it may be possible to meet the cost goals by optimizing design using Computer Aided Engineering (CAE), and minimizing expenses related to manufacturing.

In a major study structure analyses using CAE and Design of Experiment (DoE) were carried out by a joint venture of Korean institutes: The Tongmyong University in Busan, the Korea Institute of Machinery & Materials in Taejon, the Seojeong College in Gyeonggi-do, and the Ssang Yong Motor Company. In this study, a new link shape was suggested by adding vertical ribs to an existing I-beam type link. The Institutes investigated how each design parameter makes an effect on weight, maximum von Mises stress and stiffness.

The steel made track rod of rear chassis components of a sport utility vehicle (SUV) was determined to reduce its weight using aluminum material. The track rod will be produced by a liquid metal forging process, which has less shrinkage cavity, pin hole and blow hole and better mechanical characteristics compared to the low pressure die casting process.

In this process in order to apply the liquid metal forging process by a slanted die, a basic angle must be given which was one constraint of design. The minimum size must be bigger than 8 mm in order to make the liquid metal flow smoothly in the die, which was another constraint of design.

Design of Experiment (DoE) for 64 cases of the full factorial design with 6 parameters and 2 levels was performed. One end of the track rod was completely fixed and the other end was subjected to x-, y-, or z-direction load. For each case, weight, stiffness and maximum von Mises stress were calculated. Criteria in reliability were that the stiffness was equal or more than that of the existing steel component and maximum von Mises stress was equal or less than 20% of ultimate tensile strength.

In order to investigate how much each design parameter influences the weight and stiffnesses, analysis of variance was performed for the stiffness under each load and weight. The larger the dimension of the parameter was, the higher the stress was and vice versa.

The 3 parameters most effective on stiffness and weight, the width of the link, the height of the vertical rib, and the thickness of the rib, were determined. The dimension of the track rod was optimized using FE analyses for the DoE cases of full factorial design and through response surface analysis. The weight of the aluminum track rod obtained was less than 2/3 of that of the initial steel track rod. The stiffness of the aluminum rod was remarkably increased.

J.-H. Park et al., Materialwissenschaft und Werkstofftechnik ; DOI: 10.1002/mawe.201000614