High-static low-dynamic stiffness systems: a study on quasi-zero stiffness mechanisms for optimal vibration isolation

Mechanical vibrations pose significant challenges in a multitude of industries. They potentially cause damage to structures and subsystems, discomfort to users, and interference with equipment performance and lifetime. Effective vibration isolation and damping are therefore essential. Vibration isolation is typically achieved using a soft material or compliant mechanism with a relatively low stiffness. However, an isolator with a low stiffness may result in instability and large deflections, and would be unable to handle large loads. On the other hand, if the isolator stiffness is too high, the natural frequency would be high and thereby, the isolation frequency range would be smaller. Quasi-zero stiffness (QZS) devices offer a promising solution to this conflicting requirement by exhibiting high-static low-dynamic (HSLD) stiffness properties. These devices can support large static loads while demonstrating near-zero stiffness for dynamic loads. This leads to systems with low natural frequencies and enhanced vibration isolation over a broad frequency range. This paper discusses the proof-of-concept design, fabrication, analysis and testing processes of three QZS device configurations: the simple spring, cam-roller spring (CRS), and slider-block spring (SBS) devices. Firstly, a systematic method of QZS device design and analysis is presented, where the set of optimal design parameters is obtained for each device. Secondly, the static and dynamic behaviors of these devices are calculated and compared through numerical calculations and real-world testing. Device transmissibility is analyzed in a wide range of frequencies from 5-2000 Hz: values derived from standardized aerospace testing criteria. Finally, the applicability of QZS devices across various industries is discussed. Results from numerical calculations and testing show that QZS devices have significantly better isolation performance in the low-frequency.