Methodology to Measure BIW Torsional Stiffness and Study to Identify and Optimize Critical Panels

BIW (Body-in White) is a type of vehicle structure formed by spot welding of different sheet metal components. The BIW structure should be designed to support the maximum load potential under various performance conditions. Thus the structure should have good strength as well as stiffness. Torsion Stiffness of BIW is the amount of torque required to cause a unit degree of twist. It is often considered as a benchmark of its structural competence due to its effect on various parameters like ride, handling, lateral load distribution and NVH performance of vehicle. The paper aims to design and develop a test methodology and test fixtures for measuring the BIW torsion stiffness with repeatability of test results and also have an (R²>0.99) for the measured values in the test.

Apart from establishing a method for evaluating torsional stiffness, we have introduced a parameter stated as effectiveness that would provide the information regarding the most effective panel affecting the torsional stiffness. Further the concept of effectiveness is extended to find out the most effective cross-section for an optimization of the weight changes due to the design modification and the amount of improvement in torsional stiffness. Effect of global parameter like wheelbase on torsional stiffness has been also discussed. This project will aid in new product development and benchmarking activities.