Systematic Approach for Optimizing Tailgate Stoppers and their Location to Prevent Squeak and Rattle

Tailgate stoppers play vital role in exerting pre-load on the tailgate latch mechanism and also restrict the relative motion of the tailgate against vehicle Body in White (BIW). These stoppers act as dampeners and reduce the transmissibility of vibrations thereby reduce the risk of Squeaks & Rattles (S&R) noises. These noises from tailgate are most annoying to the rear passengers in the vehicle and are recurring in nature. S & R risk simulations reduce cost by eliminating most of the design changes that are required in the physical prototype at the later stages of product development cycle and save time. The risk evaluation in the simulations is based on the relative displacement at the interfaces of two components. These interfaces are represented by Evaluation Lines (E-Lines) which are nothing but a series of nodes at the interface locations. The tailgate stoppers are modeled using a spring element with stiffness calculated from force deflection experiments. The variations due to the manufacturing process are addressed through the statistical analysis of tolerances provided for the design gaps. In this work, simulations are carried out using Squeak and Rattle Director (SnRD) on a compact UV tailgate to optimize the stiffness, location and number of stoppers required. To arrive at the optimum stiffness of the stoppers the force exerted is calculated based on the relative displacement at the interfaces identified. The location effectiveness is studied through series of simulations by placing the pair of stoppers at three different locations (Near the lifting mechanism, middle of the tailgate and Near to Latch). This is fully dependent on shape and size of the tailgate. Modal analysis and interface relative displacement results helped us in finalizing the optimum configuration. This exercise helped us in understanding the behavior of tailgate with different stopper configurations under different input excitation. This approach has helped to have first time right design and same was concurred in the physical testing; demonstrating very good correlation between digital and physical validation methods.