Torsional Stiffness Analysis Of Tubular Space-frame Chassis 2019-28-0033
Torsional Stiffness is required in an automotive when there is a lateral load transfer as it happens during turning. It also occurs when there is bump on one side of a chassis while droop on the other. A torsionally stiff chassis would provide better stability and uniform load transfer in an automotive. The lateral members in a chassis play a crucial role in increasing the torsional stiffness but they result in increased weight. The relation between mass and structural stiffness of a chassis is crucial to optimize the dynamics of an automotive. The current trends in research aim at increasing the torsional stiffness and optimizing mass for the same and thus increasing the stiffness to mass ratio. This is validated with the help of various FEA softwares. The different cases involved in real world scenario are simulated and then the stiffness is optimized accordingly. This FEA analysis is further validated using experimental analysis. An experimental jig is fabricated and setup for every condition. Static conditions are used for both FEA and experimental analysis. A list of error reducing measures has been put in place and unavoidable errors have been taken into account. The deviation of the experimental stiffness has been plotted along with the results in FEA and the possible reasons have been taken into account. The variations present in the fabricated chassis lead to the deviation from the designed model. The chassis is then optimized after performing an uncertainty analysis. There is a certain loss of torsional stiffness in every cycle which occurs due to loss by torsional hysteresis.
Since in the real world conditions the chassis would be under motion the correct validation should be by an explicit dynamic analysis performed on the FEA software. The experimental analysis should also be designed in a dynamic environment using data acquisitions. The noise and vibrations of the chassis under the load transfer conditions need to be taken to obtain a more optimal solution. The losses due to torsional hysteresis need to be studied. A method of optimization needs to be devised to understand and reduce the torsional hysteresis losses and its relation with the fatigue life of the chassis. The objective of this paper is to design, analyze and optimize the torsional stiffness of a prototype automotive chassis.