Suppression of Internal Resonances of Rubber Isolators Using Dynamic Vibration Absorbers

This paper presents methods to improve the performance of rubber isolators by controlling their Internal Resonances (IRs). IRs are associated with isolators’ internal elastic motions that are due to their inertia. It is well known that IRs degrade the isolator performance as predicted by ideal massless isolator models. However, to the best of the authors’ knowledge, there are no reported works on the suppression of such IRs to improve the isolator performance. This paper proposes two novel approaches to suppress IRs. The first approach uses passive dynamic vibration absorbers (PDVA’s) directly embedded into the isolator. The effectiveness of this approach is investigated analytically using a three degree-of-freedom vibration model. It is shown that the PDVA’s are very effective in attenuating the IRs and improve the isolator’s performance at high frequencies. However, the PDVA’s are ineffective at low frequencies. To overcome this limitation, an active control force is added between the DVA masses, forming the hybrid DVA (HDVA) approach. The effectiveness of both the PDVA and the HDVA approaches is demonstrated experimentally. It is shown that, compared to the original isolator, in the isolation region of the experimental system, adding PDVA’s reduces the force transmissibility by 18.5% and the overall noise radiated by the foundation by 4.3 dB. Furthermore, the HDVA approach reduces the force transmissibility and radiated noise by 92.2% and 9.1 dB, respectively.