Nonlinear Dynamic Response of an Isolation System With Negative Stiffness and Shape Memory-Based Damping

2020 ◽  
Author(s):  
Andrea Salvatore ◽  
Biagio Carboni ◽  
Walter Lacarbonara
Keyword(s):  
Shape Memory ◽  
Damping Ratio ◽  
Dynamic Performance ◽  
Excitation Amplitude ◽  
Negative Stiffness ◽  
Response Curves ◽  
Nonlinear Dynamic Response ◽  
Isolation System ◽  
Hysteretic Damping ◽  
Different Levels

Abstract The negative stiffness offered by bi-stable mechanisms can improve the dynamic performance of a structure. In this work the effects of adding negative stiffness and shape memory alloy (SMA) damping in base-isolated structures are explored through the study of the stationary response for different values of negative stiffness and SMA hysteretic damping ratio. The frequency response curves of the isolated structure, with and without the negative stiffness contribution, are numerically obtained for different levels of excitation amplitude in order to evaluate the acceleration and displacement transmissibility curves. The benefits of negative stiffness, damping amplification and reduced transmissibility of accelerations and displacements, as well as the existence of dynamic instabilities, are illustrated.

scholarly journals Nonlinear dynamic response of a Negative Stiffness-Shape Memory Alloy isolation system

2021 ◽  
Author(s):  
Andrea Salvatore ◽  
Biagio Carboni ◽  
Walter Lacarbonara
Keyword(s):  
Shape Memory Alloy ◽  
Dynamic Response ◽  
Shape Memory ◽  
Nonlinear Dynamic ◽  
Vibration Isolation ◽  
Extensive Study ◽  
Negative Stiffness ◽  
Response Curves ◽  
Nonlinear Dynamic Response ◽  
Isolation System

Abstract The negative stiffness exhibited by bi-stable mechanisms together with tunable hysteresis in the context of vibration isolation devices can enhance the dynamic resilience of a structure. The effects of negative stiffness and shape memory alloy (SMA) damping in base-isolated structures are here explored by carrying out an extensive study of the nonlinear dynamic response via pathfollowing, bifurcation analysis, and time integration. The frequency-response curves of the isolated structure, with and without the negative stiffness contribution, are numerically obtained for different excitation amplitudes to construct the acceleration and displacement transmissibility curves. The advantages of negative stiffness, damping augmentation and reduced accelerations and displacements transmissibility, as well as the existence of rich bifurcation scenarios giving rise to quasi-periodicity and synchronization, are extensively illustrated.

scholarly journals Design and Characteristics Analysis of a Nonlinear Isolator Using a Curved-Mount-Spring-Roller Mechanism as Negative Stiffness Element

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Han Junshu ◽  
Meng Lingshuai ◽  
Sun Jinggong
Keyword(s):  
Damping Ratio ◽  
Harmonic Balance Method ◽  
Excitation Amplitude ◽  
Negative Stiffness ◽  
Response Curves ◽  
Restoring Force ◽  
Characteristics Analysis ◽  
Stiffness Softening ◽  
Isolation Performance ◽  
Cubic Stiffness

The characteristics of a passive nonlinear isolator are developed by combining a curved-mount-spring-roller mechanism as a negative stiffness corrector in parallel with a vertical linear spring. The static characteristics of the isolator are presented, and the configurative parameters are optimized to achieve a wider displacement range at the equilibrium position where the isolator has a low stiffness and the stiffness changes slightly. The restoring force of the isolator is approximated using a Taylor expansion to a cubic stiffness. Considering the overload and underload conditions, a dynamic equation is established as a Helmholtz-Duffing equation, and the resonance response of the nonlinear system is determined by employing the harmonic balance method (HBM). The frequency response curves (FRCs) are obtained for displacement excitations. The absolute displacement and acceleration transmissibility are defined and investigated to evaluate the performance of the nonlinear isolator, and they are compared with an equivalent linear isolator that can support the same mass with the same static deflection as the proposed isolator. The effects of the amplitude of the excitation, the offset displacement, and the damping ratio on the dynamic characteristics and the transmissibility performance are considered, and experiments are carried out to verify the above analysis. The results show that the overload and underload system can outperform the counterparts with the linear stiffness, softening stiffness, softening-hardening stiffness, and hardening stiffness with the magnitude of the excitation amplitude, and that its isolation performance is generally better than that of a linear system. The transmissibility, response, and resonance frequency of the system are affected by the excitation amplitude, offset displacement, cubic stiffness, and damping ratio. To obtain a better isolation performance, an appropriate mass, not-too-large amplitude, and larger damper are necessary for the proposed isolator.

scholarly journals Nonlinear dynamic response of an isolation system with superelastic hysteresis and negative stiffness

2021 ◽  
Author(s):  
Andrea Salvatore ◽  
Biagio Carboni ◽  
Walter Lacarbonara
Keyword(s):  
Dynamic Response ◽  
Nonlinear Dynamic ◽  
Vibration Isolation ◽  
Time Integration ◽  
Extensive Study ◽  
Negative Stiffness ◽  
Response Curves ◽  
Nonlinear Dynamic Response ◽  
Isolation System ◽  
Isolated Structures

AbstractThe negative stiffness exhibited by bi-stable mechanisms together with the tunable superelasticity offered by shape memory alloy (SMA) wires can enhance the dynamic resilience of a structure in the context of vibration isolation. The effects of negative stiffness and superelastic damping in base-isolated structures are here explored by carrying out an extensive study of the nonlinear dynamic response via pathfollowing, bifurcation analysis, and time integration. The frequency-response curves of the isolated structure, with and without the negative stiffness contribution, are numerically obtained for different excitation amplitudes to construct the acceleration and displacement transmissibility curves. The advantages of negative stiffness, such as damping augmentation and reduced acceleration/displacement transmissibility, as well as the existence of rich bifurcation scenarios toward quasi-periodicity and chaos, are discussed.

Geotechnical Seismic Isolation System - Experimental Study

2010 ◽  
Vol 163-167 ◽  
pp. 4449-4453
Author(s):  
Wei Xiong ◽  
Hing Ho Tsang ◽  
S.H. Lo ◽  
Shou Ping Shang ◽  
Hai Dong Wang ◽  
...  
Keyword(s):  
Seismic Isolation ◽  
Dynamic Performance ◽  
Testing Procedure ◽  
Shaking Table ◽  
Isolation System ◽  
Isolation Technique ◽  
Sand Mixture ◽  
Seismic Hazard Mitigation ◽  
Constituent Material ◽  
Different Levels

In this study, an experimental investigation program on a newly proposed seismic isolation technique, namely “Geotechnical Seismic Isolation (GSI) system”, is conducted with an aim of simulating its dynamic performance during earthquakes. The testing procedure is three-fold: (1) A series of cyclic simple shear tests is conducted on the key constituent material of the proposed GSI system, i.e., rubber-sand mixture (RSM) in order to understand its behavior under cyclic loadings. (2) The GSI system is then subjected to a series of shaking table tests with different levels of input ground shakings. (3) By varying the controlling parameters such as percentage of rubber in RSM, thickness of RSM layer, coupled with the weight of superstructure, a comprehensive parametric study is performed. This experimental survey demonstrates the excellent performance of the GSI system for potential seismic hazard mitigation.

scholarly journals Design, Experiment, and Improvement of a Quasi-Zero-Stiffness Vibration Isolation System

2020 ◽  
Vol 10 (7) ◽  
pp. 2273 ◽  
Author(s):  
Shuai Wang ◽  
Wenpen Xin ◽  
Yinghao Ning ◽  
Bing Li ◽  
Ying Hu
Keyword(s):  
Vibration Isolation ◽  
Damping Ratio ◽  
Excitation Amplitude ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Linear Spring ◽  
Isolation Effects ◽  
Magnetic Rings ◽  
The Relationship ◽  
Force Displacement

This paper proposes a new kind of quasi-zero-stiffness (QZS) isolation system that has the property of low-dynamic but high-static stiffness. The negative stiffness was produced using two magnetic rings, the magnetization of which is axial. First, the force–displacement characteristic of the two coupled magnetic rings was developed and the relationship between the parameters of the magnetic rings and the stiffness of the system was investigated. Then, the dynamic response of the QZS was analyzed. The force transmissibility of the system was calculated and the effects of the damping ratio and excitation amplitude on the isolation performance were investigated. The prototype of the QZS system was developed to verify the isolation effects of the system based on a comparison with a linear vibration isolation platform. Lastly, the improvement of the QZS system was conducted based on changing the heights of the ring magnets and designing a proper non-linear spring. The analysis shows the QZS system after improvement shows better isolation effects than that of the non-improved system.

scholarly journals Theoretical Design and Characteristics Analysis of a Quasi-Zero Stiffness Isolator Using a Disk Spring as Negative Stiffness Element

2015 ◽  
Vol 2015 ◽  
pp. 1-19 ◽  
Author(s):  
Lingshuai Meng ◽  
Jinggong Sun ◽  
Wenjuan Wu
Keyword(s):  
Damping Ratio ◽  
Low Frequency ◽  
Harmonic Balance Method ◽  
Steady State Solution ◽  
Excitation Amplitude ◽  
Response Curves ◽  
Disk Spring ◽  
Performance Effects ◽  
Characteristics Analysis ◽  
Isolation Performance

This paper presents a novel quasi-zero stiffness (QZS) isolator designed by combining a disk spring with a vertical linear spring. The static characteristics of the disk spring and the QZS isolator are investigated. The optimal combination of the configurative parameters is derived to achieve a wide displacement range around the equilibrium position in which the stiffness has a low value and changes slightly. By considering the overloaded or underloaded conditions, the dynamic equations are established for both force and displacement excitations. The frequency response curves (FRCs) are obtained by using the harmonic balance method (HBM) and confirmed by the numerical simulation. The stability of the steady-state solution is analyzed by applying Floquet theory. The force, absolute displacement, and acceleration transmissibility are defined to evaluate the isolation performance. Effects of the offset displacement, excitation amplitude, and damping ratio on the QZS isolator and the equivalent system (ELS) are studied. The results demonstrate that the QZS isolator for overloaded or underloaded can exhibit different stiffness characteristics with changing excitation amplitude. If loaded with an appropriate mass, excited by not too large amplitude, and owned a larger damper, the QZS isolator can possess better isolation performance than its ELS in low frequency range.

scholarly journals Measurement Research of Motorized Spindle Dynamic Stiffness under High Speed Rotating

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Xiaopeng Wang ◽  
Yuzhu Guo ◽  
Tianning Chen
Keyword(s):  
High Speed ◽  
Production Efficiency ◽  
Dynamic Stiffness ◽  
Damping Ratio ◽  
Dynamic Performance ◽  
Machining Accuracy ◽  
Motorized Spindle ◽  
Response Curves ◽  
Tool Technology ◽  
High Speed Machine

High speed motorized spindle has become a key functional unit of high speed machine tools and effectively promotes the development of machine tool technology. The development of higher speed and more power puts forward the stricter requirement for the performance of motorized spindle, especially the dynamic performance which affects the machining accuracy, reliability, and production efficiency. To overcome the problems of ineffective loading and dynamic performance measurement of motorized spindle, a noncontact electromagnetic loading device is developed. The cutting load can be simulated by using electromagnetic force. A new method of measuring force by force sensors is presented, and the steady and transient loading force could be measured exactly. After the high speed machine spindle is tested, the frequency response curves of the spindle relative to machine table are collected at 0~12000 rpm; then the relationships between stiffness and speeds as well as between damping ratio and speeds are obtained. The result shows that not only the static and dynamic stiffness but also the damping ratio declined with the increase of speed.

Displacement mitigation–oriented design and mechanism for inerter-based isolation system

2020 ◽  
pp. 107754632095166 ◽  
Author(s):  
Zhipeng Zhao ◽  
Ruifu Zhang ◽  
Nicholas E Wierschem ◽  
Yiyao Jiang ◽  
Chao Pan
Keyword(s):  
Damping Ratio ◽  
Dynamic Performance ◽  
Fundamental Equation ◽  
Design Procedure ◽  
Target Displacement ◽  
Design Strategies ◽  
Isolation System ◽  
Demand Equation ◽  
Isolation Layer ◽  
Displacement Demand

The inerter-based isolation system, which comprises an inerter, a dashpot, and a spring, has been shown to be effective for improving the dynamic performance of isolated structures. However, the underlying theoretical basis of its vibration control mechanism has not been studied for superstructures with inerter-based isolation system; in particular, the functionality of the inerter has not been explicitly demonstrated. In this study, the displacement mitigation mechanism is established by deriving a fundamental equation, designated as the displacement demand equation. The mechanism is explained by clarifying the functionality of the inerter-based isolation system to determine the theoretical relationship between the displacements of the superstructure and isolation layer. A nominal displacement demand ratio is defined to evaluate the overall displacement demand of the structure–inerter-based isolation system, by considering the contribution of the inerter-based isolation system. Following the displacement mitigation mechanism, design strategies are developed for inerter-based isolation system, where the isolation frequency ratio can be directly determined once the target displacement performance of the entire structure–inerter-based isolation system is prespecified. In addition, the inertance-mass ratio and damping ratio of the inerter-based isolation system can be obtained according to the target demand of the superstructure displacement. Finally, a series of examples are used to verify the derived displacement demand equation and proposed design strategy. In this study, the displacement mitigation mechanism yields an effective design method that is suitable for the inerter-based isolation system and has a clear physical basis. Through the proposed displacement mitigation–oriented optimal strategy, a target displacement demand for a structure can be satisfied directly, which also provides an optimized displacement performance for the isolation layer. The displacement mitigation mechanism and equation are practical for the simplification of the design procedure and help to reveal the advantageous features of the inerter-based isolation system.

Application of Energy Method for Determining Loss Factor in Dynamic Systems with Hysteretic Damping

2014 ◽  
Vol 580-583 ◽  
pp. 2978-2982
Author(s):  
Vladimir Smirnov ◽  
Vladimir Mondrus
Keyword(s):  
Energy Method ◽  
Loss Factor ◽  
Seismic Isolation ◽  
Vibration Isolation ◽  
Damping Ratio ◽  
Experimental Investigations ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Hysteretic Damping ◽  
Different Types

The article studies the energy method for determining loss factor due to hysteretic damping in systems of vibration and seismic isolation. Typical measure of damping is, where φ is the phase angle between stress and strain sinusoids [1], or damping constant δ ( [2, 3]). Both of these parameters are acquired through experimental investigations for each type of boundary conditions or element’s cross section. Proposed energy method is capable of loss factor ψ determination for different types of beams based on only one experimental investigation. This method is used in the paper to determine the damping ratio of elastic element in vibration isolation system of precision equipment.

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