Experimental and numerical analysis of rubber isolator dynamic stiffness under hydrostatic pressure

Due to their function in damping and attenuating vibrations, as well as their relatively low cost, rubber isolators have widespread applications in industries such as aerospace, automotive and maritime. As components with distinct nonlinear behavior, accurately predicting the dynamic characteristics of isolators is essential for overall structural design and vibration noise prediction. Although extensive research has been conducted on the static and dynamic performance of rubber isolators, there has been limited investigation into performance under certain specialized application scenarios, such as hydrostatic pressure environments. These environments are indeed real, for instance, isolators employed in the bow ballast tank of underwater vehicle to mitigate vibrations during weapon launch processes. In such instances, isolators are subjected not only to the influence of added mass due to the water medium during vibration but also to increasing hydrostatic pressure on the isolator surface with increasing depth. This study introduces an original experimental apparatus capable of measuring the dynamic stiffness of isolators while simulating hydrostatic pressure conditions. The constitutive model parameters governing the hyperelastic and viscoelastic properties of rubber were identified via nonlinear tests, serving as input parameters for numerically predicting the dynamic stiffness within a water medium environment. Furthermore, a comprehensive analysis was conducted to evaluate the impacts of preload, water medium, boundary conditions, and hydrostatic pressure on the dynamic stiffness of the isolator. Results indicate that preload tends to reduce peak dynamic stiffness in the shear directions, while the water medium significantly increases high-frequency dynamic stiffness in the shear directions. Within the range of 1 MPa, the impact of increasing hydrostatic pressure on dynamic stiffness can be largely disregarded. When calculating the dynamic stiffness of the isolator, it is crucial to consider the actual installation environment and set the acoustic boundary conditions of the surrounding water domain accordingly.