Design of a Variable Stiffness Impact Damper Using Magnetorheological Elastomers

The suppression and control of mechanical vibrations, shock, and impacts is a subject of great interest for different areas of engineering, due to their potential negative effects, such as noise, fatigue, and mechanical failure in general. This is particularly important for the aerospace and automotive industries where in addition weight reduction is paramount. Usually, isolation and suppression methods are used either in the form of resilient isolators intended to absorb and dissipate the energy or in the form of tuned mass dampers. However, recently the applications where nonlinear elements are implemented have become more relevant. A particular nonlinear strategy for vibration and shock suppression is the impact dampers. These devices work on the principle of transferring momentum from the vibrating structure to the damper through impacts between them. There are several proposed designs of impact dampers, either configured as an end stop, also called vibro-impact attachments, or particle impact dampers, where small particles are contained into a vibrating structure or attached to it, and the collisions between the particles and the confinement result in energy dissipation and thus vibration suppression. In this work, the design of a variable stiffness impact damper is proposed. By controlling the stiffness of the damper, the amount of energy absorption and dissipation can be enhanced during impacts. To build the impact damper, a magnetorheological elastomer (MRE) is considered. These elastomers are manufactured using silicone rubber with embedded ferromagnetic particles, achieving stiffness variation through the application of a magnetic field. The design and modeling of the damper using a nonlinear geometry is introduced, and then prototypes are manufactured and experimentally quantified in terms of their capacity to change stiffness when a magnetic field is applied, as well as the energy absorption and vibration suppression capabilities. The advantages and limitation of the proposed design are then presented and discussed. It is found how the impact damper with variable stiffness can improve the vibration suppression under certain conditions depending on the level of the impact and the stiffness change obtained. Discussion about further control strategies and implementation are presented.