A Method of Evaluating the Joint Effectiveness on Contribution to Global Stiffness and NVH Performance of Vehicles

While Advanced High Strength Steels (AHSS) and the next generation AHSS grades offer improved crash safety and reduced weight for vehicles, the global stiffness and NVH performance are often compromised due to reduced material thickness. This paper discusses an advanced method of evaluating the joint effectiveness on contribution to global stiffness and NVH performance of vehicles. A stiffness contribution ratio is proposed initiatively in this research, which evaluates the current contribution of the joints to the global stiffness and NVH performance of vehicles. Another parameter, joint effectiveness factor, has been used to study the potential of each joint on enhancing the global stiffness. The critical joints to enhance the vehicle stiffness and NVH performance can be identified based on above two parameters, and design changes be made to those critical joints to improve the vehicle performance. A Ford sedan BIW model was adopted in this study to demonstrate this method and torsion stiffness was chosen as the enhancement target. Based on this method, the global torsion stiffness, as well as bending stiffness and vibration modes, can be improved by enhancing the critical joints identified in this joint effectiveness study. Mass reduction target can also be achieved by degrading the joints that are found not efficient to global vehicle performance.