Shock isolation characteristics of a bistable vibration isolator with tunable magnetic controlled stiffness

2021 ◽  
pp. 1-28
Author(s):  
Bo Yan ◽  
Peng Ling ◽  
Yanlin Zhou ◽  
Chuan-yu Wu ◽  
Wen-Ming Zhang
Keyword(s):  
Damping Ratio ◽  
Excitation Amplitude ◽  
Relative Displacement ◽  
Vibration Isolator ◽  
Maximum Acceleration ◽  
Vibration Isolators ◽  
Displacement Ratio ◽  
Shock Isolation ◽  
Maximum Relative Displacement ◽  
Isolation Performance

Abstract This paper investigates the shock isolation characteristics of an electromagnetic bistable vibration isolator (BVI) with tunable magnetic controlled stiffness. The theoretical model of the BVI is established. The maximum acceleration ratio (MAR), maximum absolute displacement ratio (MADR) and maximum relative displacement ratio (MRDR) are introduced to evaluate the shock isolation performance of the BVI. The kinetic and potential energy are observed to further explore the performance of the BVI. The effects of the potential barrier, shape of potential well, damping ratio on the BVI are discussed compared to the linear vibration isolators (LVI). The results demonstrate that the intrawell oscillations and snap-through oscillations are determined by the excitation amplitude and duration time of main pulse. MADR and MRDR of the BVI are smaller than those of the LVI. The maximum acceleration peak amplitude of the BVI is far below that of the LVI, especially when the snap-through oscillation occurs. In brief, the proposed BVI has a better shock isolation performance than the LVI and has the potential to suppress the shock of space structures during the launch and on-orbit deploying process.

Analysis of Frequency and Damping Ratio on the Shock Isolation Efficiency

2013 ◽  
Vol 791-793 ◽  
pp. 835-838
Author(s):  
Shi Jie Wu ◽  
Lin He ◽  
Xi Zhi Zhao
Keyword(s):  
Damping Ratio ◽  
Relative Displacement ◽  
Displacement Amplitude ◽  
Vibration Isolator ◽  
Isolation System ◽  
Single Degree Of Freedom ◽  
Absolute Acceleration ◽  
Single Degree ◽  
Acceleration Amplitude ◽  
Shock Isolation

The traditional shock isolation system is only designed in stiffness regardless of damping, which causes acute contradiction between absolute acceleration amplitude and relative displacement amplitude. Based on the single degree of freedom negative shock isolation system, numerical analysis demonstrates that relative little amplitude of absolute acceleration and relative displacement could be attained within a certain range of damping and frequency ratio. Selecting appropriate damping and stiffness of vibration isolator can resolve contradiction between absolute acceleration amplitude and relative displacement amplitude and consequently improve shock isolation efficiency.

Beneficial performance of a quasi-zero stiffness vibration isolator with generalized geometric nonlinear damping

2020 ◽  
pp. 095745652097238
Author(s):  
Chun Cheng ◽  
Ran Ma ◽  
Yan Hu
Keyword(s):  
Damping Ratio ◽  
Nonlinear Damping ◽  
Vibration Isolator ◽  
Equivalent Damping ◽  
Frequency Responses ◽  
Geometric Nonlinear ◽  
Resonant Region ◽  
Force Transmissibility ◽  
Isolation Performance ◽  
Force And Displacement Transmissibility

Generalized geometric nonlinear damping based on the viscous damper with a non-negative velocity exponent is proposed to improve the isolation performance of a quasi-zero stiffness (QZS) vibration isolator in this paper. Firstly, the generalized geometric nonlinear damping characteristic is derived. Then, the amplitude-frequency responses of the QZS vibration isolator under force and base excitations are obtained, respectively, using the averaging method. Parametric analysis of the force and displacement transmissibility is conducted subsequently. At last, two phenomena are explained from the viewpoint of the equivalent damping ratio. The results show that decreasing the velocity exponent of the horizontal damper is beneficial to reduce the force transmissibility in the resonant region. For the case of base excitation, it is beneficial to select a smaller velocity exponent only when the nonlinear damping ratio is relatively large.

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 Nonlinear isolation performance of 6 × 19 wire rope of different lengths under compression

2021 ◽  
Vol 13 (6) ◽  
pp. 168781402110280
Author(s):  
Genlin Mo ◽  
Jing Liu ◽  
Yongxi Jin ◽  
Wenmin Yan
Keyword(s):  
Hysteresis Loop ◽  
Vibration Amplitude ◽  
Steel Wire ◽  
Damping Ratio ◽  
Excitation Amplitude ◽  
Wire Rope ◽  
Equivalent Damping ◽  
Wire Rope Isolator ◽  
The Wire ◽  
Isolation Performance

Stainless steel wire rope isolator is widely used in engineering. To optimize design of the isolator, loading, and unloading characteristics of the 6 × 19 6 mm wire rope under compression are investigated. Ropes of different lengths are tested to get the force-displacement relations. The stiffness, the equivalent damping ratio, and the hysteresis loop of the wire rope are derived. The stiffness decreases with both the length of the rope and the vibration amplitude. It has an approximate linear relationship with the reciprocal of length and amplitude. The equivalent damping ratio has an approximate quadratic relationship with the reciprocal of length and amplitude. The hysteresis loop of the wire rope is described using the proposed quadrilateral model. The loading stage is found to be determined by the length of the rope. The unloading stage is influenced by both the vibration amplitude and the length of the rope. Influences of the excitation amplitude and the frequency on the isolation performance for both steady-state vibration and transient impact vibration are revealed based on the models. The work would help engineers to design the isolators and predict responses of the structures.

On The Dynamics of Intermittent-Motion Mechanisms. Part 1: Dynamic Model and Response

1983 ◽  
Vol 105 (3) ◽  
pp. 534-540 ◽  
Author(s):  
Ting W. Lee ◽  
A. C. Wang
Keyword(s):  
Dynamic Models ◽  
Damping Ratio ◽  
Relative Displacement ◽  
Dynamical Response ◽  
Damping Force ◽  
Damping Material ◽  
Proposed Model ◽  
Maximum Relative Displacement ◽  
Motion Characteristics ◽  
Intermittent Motion

This paper deals with a basic problem regarding intermittent-motion mechanisms, namely, how to formulate a predicative model for the study of the dynamics of these mechanisms. A mathematical model is developed in this investigation. The model, which includes clearance, damping, material compliance, and mechanism elasticity, is basic to the determination of the dynamical response such as force amplification and motion characteristics of mechanisms with intermittent motion. A new approach in the modeling of system damping is presented. Instead of using damping ratio, which is difficult to estimate accurately, a new damping function is introduced, which characterizes the speed and load dependent nature of damping. Two types of damping functions are proposed and both of their corresponding damping forces satisfy the expected hysteresis boundary conditions, i.e., zero damping force at zero and maximum relative displacement of contact. A comparative study of the present model with conventional dynamic models is performed. It demonstrates the characteristics and the usefulness of the proposed model for the study of the dynamics of intermittent-motion mechanisms.

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.

Investigation into Central-Difference and Newmark’s Beta Methods in Measuring Dynamic Responses

2013 ◽  
Vol 831 ◽  
pp. 95-99 ◽  
Author(s):  
Behzad Mohammadzadeh ◽  
Hyuk Chun Noh
Keyword(s):  
Damping Ratio ◽  
Relative Displacement ◽  
Dynamic Responses ◽  
Dynamic Loads ◽  
Ground Acceleration ◽  
Central Difference ◽  
Earthquake Force ◽  
Central Difference Method ◽  
Require Response ◽  
Maximum Relative Displacement

Studies in the structural systems include two main approaches, design and analysis, which require response evaluation of structures to the external loads including live and dead loads. Structures behave statically and dynamically for static and dynamic loads, respectively. One of the most important dynamic loads acting on a structure is earthquake force. In order to find responses of structures subjected to earthquake, several schemes of direct integration can be used. This study deals with two methods of calculating dynamic responses of a single-degree of freedom oscillator, i.e., central difference method (CDM) and Newmarks beta method (NBM), using recorded ground acceleration for 60seconds. The maximum relative acceleration is obtained to determine maximum relative displacement by which estimation of quality and quantity of failure occurred to a structure for a given earthquake is provided. Firstly both CDM and NBM are discussed. Second, for a specific damping ratio dynamic responses are evaluated for periods of range in between 0.1sec to 1.5sec to evaluate the effects of period on responses of system. Third, the effects of damping on dynamic responses of SDOF system are evaluated by considering different damping coefficients from ζ=0 to 0.5. The results are compared and discussed to investigate the range of periods and damping factors where methods can provide a better estimation of responses.

Study on the Shock Isolation Performance of the Woodpecker’s Head

2014 ◽  
Vol 635-637 ◽  
pp. 214-218
Author(s):  
Hua Bing Mao ◽  
Qi Bai Huang
Keyword(s):  
Response Spectrum ◽  
Transient Responses ◽  
Maximum Acceleration ◽  
Isolation System ◽  
System Parameters ◽  
Shock Response ◽  
Shock Response Spectrum ◽  
Shock Isolation ◽  
Two Degree Of Freedom ◽  
Isolation Performance

The two-degree-of-freedom (two-dof) shock isolation system has been presented based on the woodpecker’s head structure. The effect of the system parameters on the performance of the shock isolation system has been studied by using transient responses and shock response spectrum. The results show that appropriate parameters can effectively reduce the maximum acceleration and displacement of the woodpecker’s brain. The discussion provides a new insight to the shock isolation mechanism of woodpecker’s head, and would be useful for the design of shock isolation.

Design and Experimental Analysis of Origami-Inspired Vibration Isolators With Quasi-Zero-Stiffness Characteristic

2016 ◽  
Author(s):  
Sachiko Ishida ◽  
Kohki Suzuki ◽  
Haruo Shimosaka
Keyword(s):  
Experimental Analysis ◽  
Frequency Region ◽  
Vibration Isolator ◽  
Spring Stiffness ◽  
Torsional Buckling ◽  
Harmonic Oscillations ◽  
Vibration Isolators ◽  
Stiffness Characteristic ◽  
Current Specification ◽  
Isolation Performance

We present a prototype vibration isolator whose design is inspired by origami-based foldable cylinders with torsional buckling patterns. The vibration isolator works as a nonlinear spring that has quasi-zero spring stiffness in a given frequency region, where it does not transmit vibration in theory. We evaluate the performance of the prototype vibration isolator through excitation experiments via the use of harmonic oscillations and seismic-wave simulations of the Tohoku-Pacific Ocean and Kobe earthquakes. The results indicate that the isolator with the current specification is able to suppress the transmission of vibrations with frequencies of over 6 Hz. The functionality and constraints of the isolator are also clarified. It has been known that origami-based foldable cylinders with torsional buckling patterns provide bistable folding motions under given conditions. In a previous study, we proposed a vibration isolator utilizing the bistability characteristics and numerically confirmed the device’s validity as a vibration isolator. Here, we attempt prototyping the isolator with the use of versatile metallic components and experimentally evaluate the isolation performance.

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