Damped Tailgate System Drop Dynamics and Evaluation of Strut Force for Durability 2020-01-0908

This paper describes a simplified CAE simulation for the calculation of peak strut force in a damped tailgate system. Tailgate systems in the past included a torsion rod for lift assist, but did not include damping in the opening/drop direction. Newer tailgate systems include a strut to provide damping during drop and possibly lift assist. These tailgates may also be designed to experience a free-fall for a few degrees after being unlatched and before the strut engages. When the latch is released, the tailgate accelerates as it falls freely and then encounters a rapidly increasing damping force as the strut engages. The deceleration of the gate depends upon the damping force, yet the damping force depends upon the deceleration of the tailgate, making a precise calculation of the damping force difficult. Damping characteristics of the strut depend on the volume, the viscosity of oil and its flow restrictions across the piston. These parameters are not known early in the design process.

This study presents a method to back calculate the damping force on a tailgate solely based on the desired drop time, and does not require physical measurements of the strut. An ABAQUS explicit analysis with beams and connectors is defined to simulate the tailgate drop event. The simulation calculates the damping force, based on a linear damping coefficient and the velocity of the strut at each incremental drop position. Peak strut force is found to occur mid-way through the drop event and is greater than the force of the fully compressed strut. The simulation shows good correlation to measured time history for strut force, tailgate drop angle and strut linear motion.