Analysis of Frequency at Minimum Dynamic Stiffness for a Hydraulic Engine Mount with Floating Decoupler under High Frequency Excitation

The primary functions of mounts include providing structural support, sound insulation, and vibration damping. Dynamic stiffness and loss angle are critical metrics for evaluating their NVH (Noise, Vibration, and Harshness) performance. This paper examines a floating decoupler hydraulic mount featuring a long decoupler membrane track. A nonlinear lumped parameter model is developed to calculate the dynamic stiffness and loss angle. The model incorporates fluid flow in the lower chamber and variations in the support reaction force of the decoupler membrane under switching conditions. Parameters of the nonlinear lumped parameter model, including rubber stiffness, equivalent piston area, and volumetric compliance of the fluid chamber, were analyzed and calculated using the finite element method. The influence of different decoupler membrane track structures on the frequency corresponding to the minimum high-frequency dynamic stiffness was investigated based on the established model. The results demonstrate that, under high-frequency and small-amplitude conditions, increasing the decoupler membrane track length and decreasing its cross-sectional area result in a lower frequency at which the minimum high-frequency dynamic stiffness occurs. Conversely, under low-frequency large-amplitude conditions, alterations in the decoupler membrane track structure have negligible impact on the dynamic characteristics. A comparison between simulation and experimental results confirms that the developed lumped parameter model accurately represents the dynamic behavior of the hydraulic mount.