Synergetic integration of elastic constraint and linkages for enhancing vibration isolation

This study proposes synergic use of elastic constraints and linkage mechanism in creating nonlinear vibration isolators to enhance their low-frequency isolation performance. The use of constraint overcomes the folding problem of linkages under large deflections and their hybrid use offers great performance benefits. The vibration-attenuation enhancement owing to the integration of nonlinear elements into a single-stage isolation system and an isolation system with a flexible foundation is investigated considering applications in marine or aerospace engineering. The harmonic-balance method (HBM) with an alternating frequency/time scheme and time-marching method are employed to calculate the responses. The performance of the proposed nonlinear isolator is experimentally validated. The vibration transmissibilities and power-transmission indices are used as measures of the isolation performance. The results show that the nonlinear isolator considerably decreases the power flow and vibration transmissibility to the base over a broad frequency range. The use of the elastic constraint enables a wider range of spring-linkage parameters in the design, and the proposed isolator can provide improved vibration-attenuation capabilities at low frequencies. With the integration of constraint and linkages, the peaks in the curves for the force transmission and power flow to the flexible foundation are significantly suppressed and shifted towards lower frequencies. A base-motion excitation experiment is conducted, and the results validate the effectiveness of the proposed nonlinear isolator, showing a lower resonant frequency and reduction in the peak displacement transmissibility. This study demonstrates that the proposed isolator design can be further applied to the isolation platform of onboard mechanical systems.