Establishing Correlation between Torsional and Lateral Stiffness Parameters of BIW and Vehicle Handling Performance

There are numerous parameters that affect the handling characteristics of ground vehicles. Among those, lateral and torsional body stiffness plays a major role. Increasing the body stiffness not only improves the handling characteristics, [1] but also other properties like crashworthiness, [6], Noise Vibration & Harshness [NVH], and durability, [2], [3]. But a body with high stiffness, demands a higher weight and cost because of the increased panel thickness required and reinforcement members. Car manufactures try to reduce the vehicle weight to improve the fuel efficiency, because this is one of the primary criteria based on which customers purchase vehicles. In the process of achieving a light weight body, the body stiffness may suffer. As a result of many earlier studies, it is known that increase in stiffness of the vehicle body improves the handling of the vehicle, [2]. But, there has been no attempt made to predict how much improvement in handling occurs for a particular increase in body stiffness. The objective of this project is to establish a Correlation between Torsional and Lateral Stiffness Parameters of Body-In-White [BIW] on Vehicle Handling Performance. The correlation obtained can be used in optimization of the initial design so that the handling of the vehicle may not suffer in the process of weight reduction.

The areas of the vehicle body that are susceptible to deformation during the static and dynamic conditions are identified using Computer Aided Engineering [CAE] Techniques. Based on the findings from CAE, various fixtures are fabricated according to the need to vary the stiffness parameters. The change in handling performance with the variation of torsional and lateral stiffness parameters is evaluated. After understanding the change in subjective performance, objective data is measured for validation of the same. The objective evaluation of the vehicle is done through standard test procedures and the variation in the handling characteristics with reference to the standard vehicle is discussed.