A two degree of freedom stable quasi-zero stiffness prototype and its applications in aseismic engineering

Zhu

Wang

et al. 2022

Preprint

Self Cite

The effective solution to avoid machinery damage caused by resonance has been perplexing the field of engineering as a core research direction since the resonance phenomenon was discovered by Leonhard Euler in 1750. Numerous attempts have been performed to reduce the influence of resonance since the middle of last century, by introducing a nonlinear structure or a closed-loop control system. However, the existed methodologies cannot eliminate the resonance completely even extra problems were introduced inevitably, which means the technical choke-point of resonance-free remains unsolved. Here we propose an inverse method based upon the requirements of dynamic characteristics of the supporting system to construct a passive archetypal model with zero-stiffness within a designable distance to avoid the resonance. The reliability of the inverse method is demonstrated theoretically and experimentally, which indicate that the constructed system with zero-stiffness can outright eliminate the mechanical resonance by completely isolating the energy transfer between the load and environment. The distinctive geometric characteristics of the zero-stiffness system leads to a new inspiration for the design of resonance-free passive mechanisms or metamaterials, and the inverse method can even adapt the design for a more targeted application based on an arbitrary complex dynamic requirement.

“…Therefore, the QZS n system can always be constructed by introduce a curve function conforming to the form of (32), with the undetermined coefficients determined by (7).…”

Section: Construction Of Qzs Nmentioning

confidence: 99%

mentioning

confidence: 99%

Road to entire insulation for resonances

Zhu

Wang

et al. 2022

Preprint

Self Cite

“…The most acceptable model of nonlinear structure with SQZS is based upon the SD oscillator [17,18], which was firstly introduced in 2006 by Cao [19] and is deeply developed recently [20][21][22][23][24][25][26]. The SD oscillator is described in Fig.…”

Section: Introductionmentioning

confidence: 99%

An Archetypal Vibration Isolator with Quasi-zero Stiffness in Multiple Directions

Zhu

et al. 2022

J Nonlinear Math Phys

Self Cite

To avoid the failure under the longitudinal, shear, and mixed wave from earthquake, an archetypal vibration isolator based on a smooth and discontinuous (SD) oscillator is proposed. This model comprises a lumped mass mounted by a vertical spring and a horizontal elastic continuum, which separately provides positive and the negative stiffness forming the stable quasi-zero stiffness (SQZS) in all vertical and horizontal directions. The equation of motion is formulated by employing the Lagrange equation, and the SQZS condition is obtained by optimizing the geometrical parameters of the system. The analysis shows that the system admits remarkable performance in vibration isolation with low resonant frequency and a large stroke of SQZS interval. The results also demonstrate the system has improved aseismic behaviour under the complex excitation of seismic wave significantly.

“…In the past few years, various configurations of the QZS isolator [18][19][20][21][22] and nonlinear spring [23,24] have been proposed and studied. Xu et al [25] and Wang et al [26] developed a QZS isolator by utilizing the inclined springs to realize the negative-stiffness mechanism and using the vertical spring to support the payload.…”

Section: Introductionmentioning

confidence: 99%

High‐Efficiency Vibration Isolation for a Three‐Phase Power Transformer by a Quasi‐Zero‐Stiffness Isolator

Chang

Zhou

et al. 2021

Shock and Vibration

The vibrations generated by a three-phase power transformer reduce the comfort of residents and the service life of surrounding equipment. To resolve this tough issue, a quasi-zero-stiffness (QZS) isolator for the transformer is proposed. This paper is devoted to developing a QZS isolator in a simple way for engineering practices. The vertical springs are used to support the heavy weight of the transformer, while the oblique springs are employed to fulfill negative stiffness to neutralize the positive stiffness of the vertical spring. Hence, a combination of the vertical and oblique spring can yield high static but low dynamic stiffness, and the vibration isolation efficiency can be improved substantially. The dynamic analysis for the QZS vibration isolation system is conducted by the harmonic balance method, and the vibration isolation performance is estimated. Finally, the prototype of the QZS isolator is manufactured, and then the vibration isolation performance is tested comparing with the linear isolator under real power loading conditions. The experimental results show that the QZS isolator prominently outperforms the existing linear isolator. This is the first time to devise a QZS isolator for three-phase power transformers with heavy payloads in engineering practices.