Vibration Isolation Effect Research Articles

Fabrication and vibration isolation capacity of multilayer gradient metallic lattice sandwich panels

Sandwich structures have been widely used in ship, aerospace, vehicle and other fields, due to their lightweight and high load bearing properties. With the rapid development of ship stealth technology, multifunctional structures with lightweight, high loading capacity and excellent vibration reduction performances are urgently needed. To achieve the above multifunctional characteristics, we design and fabricate novel gradient metallic lattice sandwich structures via cutting and snap-fit approach. The gradient is governed by the size of the truss width. Modal test and shaking table sweep frequency test are conducted to characterize the vibration characteristics and vibration isolation performances of the structures. The frequency responses are simulated by modal superposition method, which is verified by experimental results. Furthermore, the influences of interlayer gradient, face sheet thickness and hybrid materials on the vibration performances are explored. Results show that the interlayer gradient and face sheet thickness have significant effects on the vibration characteristics of the present structures. The positive gradient structure has the best vibration isolation performance among all the gradient structures. What’s more, reducing the thickness of the face sheets and using hybrid materials are beneficial to achieve low-frequency vibration isolation effect, which can provide a reference for ship vibration and noise reduction technology.

Design and Analysis of Electromagnetic Quasi-zero Stiffness Vibration Isolator

IntroductionTo improve the low frequency isolation capability of vibration isolation system, a kind of electromagnetic quasi-zero-stiffness (QZS) vibration isolator was designed.Materials and methodsThe negative stiffness electromagnetic spring paralleled with the linear positive stiffness spring to achieve the state of QZS. The nonlinear dynamic model of vibration isolator was established. Through the combination of theoretical formula and simulation analysis, the electromagnetic force expression was obtained. The amplitude-frequency responsecharacteristics and force transmissibility was solved by harmonic balance method, and the effects of system parameters on amplitude - frequency characteristics and transmissibility was analyzed.ConclusionThe results show that the new isolator has better performance than the linear system, and the decreased damping ratio and excitation amplitude make the effects of vibration isolation of system superior.

Switch Semi-Active Control of the Floating Raft Vibration Isolation System

Switch semi-active control is introduced to improve the performance of the floating raft vibration isolation system on isolating vibration in the vicinity of the resonance frequency. A switch-controllable linear damper based on the electromagnetic damping principle is developed, whose characteristic parameters are obtained by experiment. The dynamic model of a semi-active control floating raft vibration isolation system is established, and two switch control algorithms are proposed. Algorithm 1 aims to minimize the kinetic energy of the raft, and Algorithm 2 balances minimizing the kinetic energy of the raft and minimizing the input energy of the system. The simulations of the original system, the system with the controllable damper, and the system with the damper controlled by the algorithms are carried out. The vibration acceleration responses of the foundation of the systems are used to evaluate the vibration isolation effect. The results show that the switching semi-active control using Algorithms 1 and 2 can significantly suppress the vibration of the system near the resonance frequency. Finally, the test platform of the switch’s semi-active controlled floating raft vibration isolation system is built, and the simulation results are verified by the experimental result.

Vibration isolation effects of barriers filled with ceramsite and Sand: Full-scale model test and numerical investigation

Barrier is an effective vibration isolation measure to reduce railway-induced vibrations. However, the full-scale model test is seldom conducted. In this paper, the ceramsite or the ceramsite-sand mix is first introduced as an in-filled material for wave barriers in mitigating railway-induced vibrations. A full-scale model test and a 3D finite element model with a perfectly matched layer as the absorbing boundary are used for studying the vibration isolation effects of the wave barriers in a continuous or non-continuous form. Before the test, the dynamic parameters of soil in the test site are obtained by the MASW test. The transfer function and the insertion loss due to the barriers at the fixed observation points have been experimentally investigated. Subsequently, the contour map of the wavefield, the Arias intensity, the influence of different depths, and the different ceramic ratios on the vibration isolation effect are examined by the numerical model. Results show the promising screening effectiveness of the ceramsite-sand mix barrier.

Design and Analysis of a Vibration Isolator with Adjustable High Static–Low Dynamic Stiffness

A new adjustable high static–low dynamic stiffness vibration isolator is presented to improve the effective vibration isolation frequency bandwidth. Firstly, the finite element simulation of electromagnetic positive stiffness device and negative one is carried out. Through static analysis, the mathematical expressions of force–displacement–current and stiffness–displacement–current are derived. The requirements that the system works at quasi-zero-stiffness condition near the equilibrium position are obtained. The influences of different parameters on the force transmission rate of the high static–low dynamic stiffness vibration isolation system are investigated with harmonic balance method. Finally, the experimental platform is built, and the vibration isolation performance experiment is conducted. Results show that the adjustable high static–low dynamic stiffness vibration isolator has a wider effective vibration isolation frequency range and lower peak transmissibility than the traditional one.

Energy Transfer of an Axially Loaded Beam With a Parallel-Coupled Nonlinear Vibration Isolator

Abstract Traditional vibration isolation of satellite instruments has an inherent limitation that low-frequency vibration suppression leads to structural instability. This paper explores a parallel-coupled quasi-zero stiffness (QZS) vibration isolator for an axially loaded beam, with the goal of enhancing the effectiveness of low-frequency isolation. A QZS contains two magnetic rings, which contribute negative stiffness, and one spiral spring, with positive stiffness, a combination that has high static stiffness to resolve the structural instability. The frequency response functions (FRFs) of power flow are used to measure the effectiveness of vibration isolation. The magnetic stiffness of the magnetic rings is calculated using the principle of equivalent magnetic charge. The heights, radii, and gap of the magnetic rings affect its stiffness. The parallel-coupled QZS vibration isolator of an axially loaded beam is modeled using an energy method. Based on the Galerkin truncation, harmonic balance analysis, and arc-length continuation, an approach is proposed to analyze the FRFs of power flow for the parallel-coupled QZS vibration isolation of an axially loaded beam. Numerical results support the analytical results. Both analytical and numerical results show that the power reduction of axially loaded beams with a parallel-coupled quasi-zero vibration isolation system is more significantly suppressed at low frequencies.

Analysis of double-layer vibration isolation characteristics of ship power equipment

The vibration isolation device of ship power equipment is the key equipment to protect it from damage, and its performance determines whether the ship can sail safely. To address the problem that it is difficult to achieve the optimal vibration isolation performance of ship’s double-layer vibration isolation, this paper establishes a vibration transmission theory model of ship’s power equipment double-layer vibration isolation system, derives the vibration displacement transmission rate formula based on the model, and studies the influence law of the stiffness ratio of the lower and upper layers of vibration isolation devices, the mass ratio of the intermediate raft frame to the power equipment and the damping of the upper and lower layers of vibration isolation devices on the vibration transmission. The results show that reducing the stiffness ratio of upper and lower layer vibration isolators and increasing the mass ratio of intermediate raft frame and power equipment can reduce the two resonant frequencies and narrow the interval between the two resonant frequencies, and increasing the damping of upper and lower layer vibration isolators can reduce the vibration peak at the two resonant frequencies, but the vibration isolation effect in the high frequency band becomes worse. It provides a theoretical basis for the design optimization of the double-layer vibration isolation system for ship's power equipment.

A novel environmental vibration analysis system and its application in isolation of environmental vibration induced by high-speed train in Harbin frozen soil site

Environmental vibration caused by high-speed trains and environmental noise pollution induced by such vibrations is one of the most challenging problems for sustainable urban development. One of the significant obstacles in analysis methods of vibration propagation path control is the inaccuracy caused by either over simplification of the interaction between train load and track above soil layers, or inappropriate expression of constitutive relationship and dynamic performance of soil below the track, especially in frozen soil, as difficulties and uncommonness exists in cross-application of multiple other disciplines into field of vibration and acoustics. A novel analysis system established in this paper, which is rare but very suitable for analysis of train induced environmental vibration and vibration isolation, builds a bridge for joint application of UM, ABAQUS, Python programming language and a series of derivation and calculation process, and manages to overcome the above obstacle to obtain a satisfactory solution. Field monitoring tests and accompanied numerical analysis based on parameters and properties determined by site investigation are carried out on soil vibration caused by CRH380B Harmony EMU train and its isolation at Harbin-Mudanjiang high-speed railway in China. Validations of the analysis system runs through the whole analysis process, including important processes and result data such as vertical wheel-rail force, velocity, vertical acceleration, characteristic frequency, and acceleration attenuation coefficient, etc. The results show that the established analysis system has high precision and wide application range, and vibration isolation effect with wave impeding barrier, who has better structural stability compared with other ones in cold regions under strong influence of seasonal and temperature physical effects, is excellent (vertical acceleration vibration level almost drop by more than 10 dB to below 72 dB, acceleration attenuation coefficient all below half and even a quarter in relatively close position). Blank in current research on wave impeding barrier vibration isolation of frozen soil sites in cold regions is well filled, and a dynamic response prediction formula is given and verified for the first time, which may have certain significance and reference value for other in-depth research.

Static and Dynamic Analysis of 6-DOF Quasi-Zero-Stiffness Vibration Isolation Platform Based on Leaf Spring Structure

Multi-degree-of-freedom isolator with low stiffness is a fair prospect in engineering application. In this paper, a novel 6-DOF QZS vibration isolation platform based on leaf spring structure is presented. Its bearing capacity is provided through four leaf springs, and the quasi-zero-stiffness is realized by the force balance between the central spring and the suspension spring. 6-DOF vibration isolation is realized by the ball-hinge fixed design of a leaf spring. Through static and dynamic analysis, the following conclusions are brought. The stiffness of the leaf spring and the deformation of the central spring under static load are directly proportional to the bearing capacity of the isolation table. Besides, in order to ensure that the stiffness of the system is close to zero, the stiffness of the suspension spring and the inner spring should be as similar as possible. The vertical and horizontal displacement transmissibility tests of the isolation platform are carried out, in which the jumping phenomenon in the QZS vibration isolation platform is analyzed. By improving the damping of the structure and the length of the suspension spring, the dynamic vibration isolation process of the system can be more stable, the transmissibility can be reduced, and the vibration isolation effect can be enhanced.

Lightweight and Flexible Graphene Foam Composite with Improved Damping Properties.

As an elastomer, PDMS can effectively suppress vibration in various fields in a certain temperature range by its viscoelastic behavior in the vitrification transition region, but the vibration isolation effect is poor at high temperature. In this paper, a three-dimensional graphene oxide (GO) foam is fabricated by solution processing method and freeze-drying techniques. After sequential infiltration synthesis, a GO-foam-reinforced PDMS nanocomposite (GO/PDMS) is fabricated with improved damping ability. By adjusting the content of GO, the micros-tructure of GO foam can be sensitively changed, which is crucial to the damping properties of composites. In this paper, by the dynamic mechanical analysis (DMA) of pure PDMS and five kinds of GO/PDMS composites, it is proved that the GO/PDMS composites developed in this work have reliable elasticity and viscoelasticity at 25 °C, which is 100 °C higher than the applicable temperature of pure PDMS. The storage modulus can reach 3.58 MPa, and the loss modulus can reach 0.45 MPa, which are 1.87 times and 2.0 times of pure PDMS, respectively. This GO-based nanocomposite is an ideal candidate for damping materials in passive vibration isolation devices.

Mechanical Properties of Loess and Filling Materials of High-Speed Railway Vibration Isolation Trench in Loess Area

The special properties of loess make its impact on the vibration propagation of high-speed railways different from other soils. In this study, the static and dynamic characteristics of loess were studied by static and dynamic triaxial tests. The experimental results show that when the frequency is the same, the dynamic stress-strain relationship curve moves up with the increase of the confining pressure. The frequency has little effect on the initial tangential dynamic modulus of the undisturbed loess. we studied the static and dynamic characteristics of loess and discussed the implementation methods of viscoelastic artificial boundary and infinite element boundary in high-speed rail dynamic response analysis. The vibration reduction and isolation effect of the trench with different filling materials (the concrete, gypsum, foamed plastic, and rubber) was studied. The results show that the comprehensive performance of the foamed plastics is better from the perspective of durability and stability of the vibration isolation trench wall. The research results can provide a reference for the selection of filling materials for high-speed railway vibration isolation trench in loess area.

A quasi-zero-stiffness isolator with a shear-thinning viscous damper

Quasi-zero-stiffness (QZS) vibration isolators have been widely studied, because they show excellent high static and low dynamic stiffnesses and can effectively solve low-frequency and ultralow-frequency vibration. However, traditional QZS (T-QZS) vibration isolators usually adopt linear damping, owing to which achieving good isolation performance at both low and high frequencies is difficult. T-QZS isolators exhibit hardening stiffness characteristics, and their vibration isolation performance is even worse than that of linear vibration isolators under a large excitation amplitude. Therefore, this study proposes a QZS isolator with a shear-thinning viscous damper (SVD) to improve the vibration isolation performance of the T-QZS isolators. The force-velocity relation of the SVD is obtained, and a dynamic model is established for the isolator. The dynamic responses of the system are solved using the harmonic balance method (HBM) and the Runge-Kutta method. The vibration isolation performance of the system is evaluated using force transmissibility, and the isolator parameters are analyzed. The results show that compared with the T-QZS isolators, the proposed QZS-SVD isolator achieves the lower initial vibration isolation frequency and peak value, and exhibits better vibration isolation performance at medium and high frequencies. Moreover, the proposed isolator can withstand a large excitation amplitude in the effective vibration isolation range.

Vibration isolation performance of simply supported beam installed with a negative stiffness device

A negative stiffness device composed of two horizontal pre-compression springs is proposed to isolate the vibration of the simply supported beam. The nonlinear vibration equation of simply supported beam installed with a negative stiffness device is established by using Hamilton principle first. The lower degree of freedom dynamic equation of the system is derived by using Galerkin truncation approach. The influence of support position and negative stiffness parameters on the natural frequency of the beam are obtained from the modal analysis of the free vibration system. According to the dynamic internal force of the beam, the force transmissibility at the support end is defined and the displacement transmissibility of any point on the beam is also defined to facilitate the analysis of the vibration isolation effect. The influence of negative stiffness support parameters on the amplitude–frequency curve and the transmissibility curve of the simply supported beam is discussed. The results show that the fundamental frequency of the system can be significantly reduced by the negative stiffness device, while the frequencies of high-order modes are changed a little bit only. Increasing the horizontal spring stiffness will reduce the first-order resonance frequency and the initial frequency of vibration isolation. Consequently, the aim of lower frequency vibration isolation for the simply supported beam can be achieved. This paper provides an effective approach to the vibration isolating design of flexible structures.

Study on the influence of sudden load at idle condition on vibration and vibration isolation performance of the engine mount system

Engine vibration is one of the main excitation sources of vehicle vibration. In order to study the problem of excessive vibration in the cabin of a light vehicle when the air conditioning is turned on at the idle speed, this study is conducted from the point of view of in-cylinder combustion caused by sudden load. The vibrations of the engine with the air conditioning on and off at the idle condition were studied experimentally. The results show that when the air conditioning is turned on at low idle speed, the cylinder pressure rise rate increases with the increase of fuel injection. In addition, the combustion pressure in the cylinder also increases, which leads to the increase of engine vibration. At the same time, a spectrum analysis is carried out in terms of the vibration signal in the maximum direction of the vibration intensity of the suspension system, and the vibration isolation rate is calculated. The results show that the vibration intensity at the second order is the largest, and the vibration isolation effect of the rear suspension is poor.

A Novel Low Stiffness Air Spring Vibration-Isolation Mounting System

Quasi-zero-stiffness (QZS) structures offer substantial practical benefits for facilitating the essential support and isolation of vibrational source loads aboard modern marine vessels. In order to design a compact QZS system of high bearing capacity, the article proposes a low stiffness air spring (LSAS) vibration-isolation mounting system composed of both vertical and lateral air springs. The vertical air springs support the load and isolate vibrations in the vertical direction, while the lateral air springs support the load and isolate transversal vibrations. Theoretical analyses based on a simple two-dimensional, single degree of freedom model demonstrate that the proposed novel LSAS design decreases the degree of stiffness in the support structure that would otherwise be induced by introducing lateral air springs and accordingly increases the vibration isolation effect. Moreover, optimization of the air spring parameters enables the lateral air springs to provide negative stiffness and thereby realize QZS characteristics. Experimental testing based on prototypes of a standard air spring mounting system and the proposed LSAS mounting system demonstrates that the stiffness of the proposed system is about 1/5 that of the standard system. Accordingly, the proposed structure design successfully alleviates the undesirable influence of lateral air springs on the stiffness of the mounting system.

Design and Analysis of a Pneumatic Spring Testing System for Precision Manufacturing.

The vibration isolation effect of the pneumatic spring determines the precision of the manufacturing. In this paper, in order to detect the performance of a pneumatic spring, a multi frequency band testing system with different payload is designed and developed. First, the pneumatic spring structure is analyzed, and the stiffness of the pneumatic spring is obtained based on the ideal gas model, Kelvin–Voigt model, and finite element method. Then, to verify the reliability of the system, a dynamic model of the vibration platform is established. Through an analysis of the simulation using the Simulink environment, critical parameters are determined, and the effective conditions of the vibration isolation are obtained. Based on the results from the simulation and experiment, the transmission rate is around 20% under 40 Hz vibration, and 12% under 100 Hz vibration. The pneumatic spring proves to be effective under vibrations beyond 7 H. This achievement will become an important basis for future research concerning precision manufacturing.

Bionic paw-inspired structure for vibration isolation with novel nonlinear compensation mechanism

Inspired by the compensation effect of fat pad on toes in a paw of digitigrade, a unique paw-inspired structure (PIS) is proposed and systematically investigated to explore its advantages in passive vibration isolation. The PIS consists of two key parts, one is the toe-like structure (TLS) simulated by two rods and a spring, and the other is fat pad mimicked by a pair of repulsive magnets. Based on the principle of virtual work, the static stiffness characteristics of the TLS are firstly analyzed. Then, the stiffness compensation mechanism of fat pad to toe is comprehensively studied. The hardening stiffness of the fat pad can compensate the negative stiffness of the TLS so that the PIS can realize quasi-zero stiffness (QZS) over large displacement range. It is for the first time to reveal this nonlinear stiffness compensation mechanism, which is essentially different from the conventional realization of QZS (connecting negative stiffness mechanism and linear spring in parallel). A dynamic model is established to estimate the vibration isolation performance. The displacement transmissibility derived by harmonic balance method (HBM) indicates that the PIS can achieve low resonance frequency and wide effective vibration isolation frequency band. Static tests are completed to verify effectiveness of the stiffness compensation mechanism. Tests under different external excitations (including periodic, sweep and random) show that the PIS can effectively suppress frequency components above 4 Hz. The PIS provides a new low-frequency vibration isolation method with high application prospects. And the proposed nonlinear stiffness mechanism can also be extended as a guideline to design nonlinear vibration isolators.

Research on the Vibration Isolation Characteristics of Floor Vibration Isolation Slab System under Train Operation

This study takes the vibration isolation measures of building floor vibrations induced by trains as the starting point and carries out both theoretical derivation and numerical simulation. A four‐degree‐of‐freedom (DOF) multi‐dimensional vibration isolation platform (VIP) dynamics model is established based on the theoretical research of single‐level, single‐degree‐of‐freedom vibration isolation systems. Under multi‐point excitation, the model can deduce the horizontal and vertical vibration responses of the VIP system. A comprehensive analysis of the vibration isolation performance of the VIP system on the floor and how the variation of the parameters influences the performance of the vibration isolation systems are presented. Several variables, such as the thickness, stiffness, damping ratio, and the number of isolators of the VIP system, are theoretically found to have a significant impact on the vibration isolation effect of the floor VIP system. Empirical results show that the VIP system significantly affects the vibration isolation of the building floor induced by a train and has the best vibration isolation effect on the acceleration response and the worst vibration isolation effect on the displacement response.

ПРОЕКТУВАННЯ БІЛЬШОГО ВМІСТУ КВАДКОПТЕРІВ НА КОНТРОЛЕРАХ СІМЕЙСТВА PIXHAWK CUBE

The quadrocopter’s design and configuration that capable to carry a payload of up to 30 kg based on the Pixhawk 2 Cube flight controller using Arducopter ver.4.1.5 firmware for FMUv3 devices was completed in the paper. For ensuring a flight range of 10-12 km, the using of 44000 mAh battery and payload of 10-15 kg is recommended. It has been established that when building large-sized copters, before setting up the PID controller, it’s necessary to pre-configure the parameters that are used by the PID controller. The failure to do so will often cause the aircraft to crash on its first flight. These are motor thrust linearization parameters, acceleration values for different axes and filters that go to the input of the PID controller. Experimentally tested the stability of the quadrocopter’s flight in windy weather in navigation modes for firmware Arducopter ver.4.1.5. At wind speeds up to 10 m/s with gusts up to 14-15 m/s, the flight stability was noted in automatic mode and in automatic return to the starting point mode. The high accuracy of the operation of the Ardupilot firmware navigation system was established when the cargo drop point was reached in automatic mode. The error was no more than 1.0-1.5 m at wind speed of 6-7 m/s. The effectiveness of mechanical vibration isolation for flight controllers of the Pixhawk Cube family has been experimentally established. When installing them on the frame of the copter, there is no need to use mechanical vibration decoupling. However, taking into account the low frequency of the frame oscillations from the operation of the propeller group (about 30 Hz), it’s necessary to design the frame with the frequency of natural oscillations outside this range. The using of software dynamic notch filters to reduce the impact of vibrations from running motors on the readings of the accelerometer and gyroscope is considered. On the frame of 2000 mm quadrocopter, it’s shown that such filters significantly reduce the amplitude of not only the detected fundamental frequency, but also their harmonics. The various ways of setting up actuators controlled by servos and relays for dropping loads, switching operating modes by video systems, switching on and off spraying mechanisms when using such drones in agriculture are considered.

Novel viscoelastic vibration isolating methods in space technology: A review

In the space application, various dynamic loads are applied during the launching and onboard phase. Satellites undergo various dynamic loads during separation from spacecraft and due to self- excited vibration or engine cut off during the launch phase. These loads generate random vibrations which can lead to malfunction of components. Viscoelastic materials are generally used in reducing thermal stresses, hence keeping the system closer to optimal working temperature. Viscoelastic materials are generally classified as fluids with high viscosity which enhances the effects of vibration absorption and isolation. This is done by the virtue of incompressibility of fluids. Novel materials, viz., air, oil, water, etc., are generally a popular choice due to efficient working couple with cost effectiveness. Viscoelastic materials have an advantage of being a passive isolator and hence they have excellent energy dissipation capacity to reduce micro vibration. The major materials such as rubber, elastomer, cork, foam and laminates in the form of pads or sheets are kept under the heavy equipment, heavy audio setup and delivery items. However, among all other materials, a novel material sorbothane pad has shown more promising application with better performance. It can be concluded that the isolation system consisting of a sorbothane pad can effectively reduce the micro-vibrations of the reaction wheel in the spacecraft and camera set up to enhance the image quality.