Vibration Isolation Efficiency Research Articles

Environmental impact of the vibration generated by the underwater shaking table of the National Facility for Earthquake Engineering Simulation (NFEES)

Earthquake simulation shaking tables serve as the valuable tools for investigating the seismic performance of structures, yet they can generate excessive vibrations in surrounding environments during operation. The National Facility for Earthquake Engineering Simulation (NFEES) in China, which is currently in the commissioning phase, will be the world's largest earthquake simulation research facility. Its experimental center consists of a 16 m × 16 m shaking table and two 6 m × 6 m underwater shaking tables (one movable). This study aims to investigate the environmental impact of the vibration generated by the fixed underwater shaking table. Initially, the vibrations of the surrounding ground, shaking table foundations, and adjacent simulation center are tested using the sinusoidal full-load and full-acceleration excitations generated by the shaking table. Upon analyzing the test results, it is observed that the peak ground acceleration (PGA) in the short side direction of foundation attenuates rapidly for high-frequency loading, with a maximum acceleration attenuation up to 55.95 % at distances of 0 m–20 m. The maximum acceleration of the foundation occurs at the edge of the shaking table and significant differences in acceleration are observed at various points across the foundation. The VLZmax of the simulation center is 66.85 dB, which is lower than the limit requirements of the Chinese standard GB55016. Subsequently, an overall finite element model of the surrounding soil-shaking table foundations-adjacent simulation center is established. Following the validation of the numerical model, the vibration isolation efficiency of the adjacent river course and the foundation isolation joint that separates the large shaking table foundation from the underwater shaking table foundation are assessed. Compared to the test results, numerical results show relatively minor discrepancies in the peak acceleration of the ground and the foundation, with maximum errors of 24.59 % and 21.11 %, respectively. The river course and the foundation isolation joint demonstrate better vibration isolation performance for short-wavelength waves, with a maximum vibration isolation efficiency reaching 64.71 % and 63.56 %, respectively.

Analysis and Experimental Study on Vibration Isolation Performance of Full-scale Turbofan Engine Mounting

At present, most of the turbofan engine use the articulated link mount to connect the engine to the wing, and the analysis and experimental research of articulated link mount are important means in the development of engine mount. In this paper, the vibration isolation performance analysis of a certain turbofan engine mounting was carried out, and a full-scale turbofan engine mounting vibration isolation test platform was established based on the four-terminal parameter method, and the engine simulation device - eccentric rotation excitation tester was developed, which simulates the real engine vibration through rotor imbalance, and the vibration isolation efficiency of a certain type of engine mount at the high and low pressure rotor frequency was obtained. The results show that the simulation and test results are very close, the error is within 15% at the low-frequency, and the error is within 5% at the high-frequency. The research of this paper can provide test evaluation means for my country to independently carry out the design and improvement for large passenger aircraft engine installation devices, and provide test basis for its design and finalization.

Analysis and verification of vibration isolation performance of engine mount based on low-frequency approximation method

At present, most of the turbofan engine use the articulated link mount to connect the engine to the wing. The mechanical modeling, analysis and experimental research of articulated link mount are important means in the development of engine mount. In this paper, multibody dynamics method is used to establish the dynamic theory equation for a certain type of turbofan engine mount, and the low-frequency approximation method of the MNF file is proposed, which greatly improves the calculation speed on the basis of ensuring the calculation accuracy. In addition, a full-scale engine mounting system vibration isolation performance test platform was developed, and the vibration isolation efficiency of a certain type of engine mount at the high and low pressure rotor frequency was obtained. The results show that the simulation and test results agree well, the error is within 15% at the low-frequency, and 5% at the high-frequency. This work provides theoretical method and test evaluation means for the design and improvement of large passenger aircraft engine installation devices.

Optimization of a commercial vehicle powertrain mounting system based on new rubber mounts

In order to improve the vibration isolation, environmental adaptability and development efficiency of rubber mounts, a novel rubber mount with adjustable parameters such as stiffness, support height and limit distance was proposed, and its structural composition and working principle were described. And then, a commercial vehicle was taken as the research object to conduct the calculation of mounts stiffness by employing the energy decoupling method and genetic algorithm. On the basis of the influence of cone angle, thickness and height on the ratio of axial-radial stiffness, the detailed structural design of the mounts was carried out, and the relationship between the preloading displacement and axial-radial stiffness was studied by the method of theoretical calculation and test, which made the process of the stiffness adjustment more specific and accurate. Finally, the vibration isolation performance test of the Powertrain Mounting System (PMS) before and after stiffness adjustment was completed. Results show that the adjusted PMS indicates better vibration isolation performance at idle speed and slow acceleration in place, and the new mounts can effectively improve the vibration performance of vehicle, environmental adaptability of mounts and product development efficiency.

Transmission of vertical vibration through a seat cushion at the seat pan: Effect of foam physical properties during different excitation magnitudes

The vibration characteristics of car seats directly influence the ride comfort. Polyurethane foam is the key part of a seat, and its physical parameters have an important impact on the seat. In this study, the influence of the foam thickness and foam hardness on the vibration characteristics of seat cushion with different excitation magnitudes was investigated by using transmissibility and seat effective amplitude transmissibility (SEAT) value. First, vibration tests were carried out at a vertical vibration simulator with width-limited white noise vibration frequencies from 0.5 to 20 Hz with root-mean-square (r.m.s.) values of 0.4, 0.8, and 1.2 m/s2, the acceleration at the platform and the body-foam interfaces were measured to calculate the transmissibility, and the influence of the foam physical properties on the transmissibility was analyzed. Then, the SEAT value was introduced to assess the vibration isolation efficiency of the foam cushion, and the influence of the foam physical properties of the foam cushion on the vibration isolation efficiency was analyzed. With increasing thickness of the foam and decreasing hardness of the foam at the seat pan, the peak transmissibility increased and the resonance frequency decreased. The SEAT values show that increasing the foam thickness is beneficial to the improvement of the vibration isolation efficiency of the seat, but there is a diminishing return; the combination of physical parameters of low hardness and high thickness could make the vibration isolation performance of the seat better. In addition, the nonlinearity of human-seat system during different vibration magnitude was found.

Development of shock absorber with quasi-zero stiffness effect to reduce dynamic effects on pump unit

The article is devoted to the improvement of the vibration isolation and shockproof properties of the shock absorber used in the vibration isolation compensator system of the pumping unit (PU). The set task is to create an elastic damping system with the desired low (quasi-zero) stiffness, which makes it possible to reduce the detrimental effect of pumping unit vibrations both on human health and on the equipment itself. High internal dynamic (vibration) loads are the main causes of early failure of pumping units, which are transmitted to the equipment through pipelines and foundations, mainly due to various operational factors. A promising trend in increasing the operating reliability and efficiency of pumping and power equipment is the use of a vibration-isolating compensator system (VICS). To obtain greater efficiency of vibration isolation, it is proposed to apply a modern method of vibration damping – the use of elastic mechanical systems with quasi-zero stiffness. The damping devices with a quasi-zero stiffness effect were studied. An assessment of the operability and effectiveness of these dampers at oil and gas facilities was given. Based on the information studied, a new concept of a quasi-zero stiffness damping device is proposed. The method of mathematical analysis determined its power curve. A 3D model of the damper device was built using a simulation software. The functional check of the damper was performed with mathematical modeling carried out on the computing device with the help of a specialized Ansys software that allows performing a system analysis of an object using the finite element method. The following results were obtained: the design of the damper with the effect of quasi-zero stiffness allows to widen the range of basement load transmission coefficient reduction towards low frequencies. The low rigidity of the system at the operating point ensures low values of the frequency of natural oscillations, and, consequently, high vibration isolation qualities.

Переходные процессы в активной системе виброизоляции с инерционным компенсатором виброактивных сил

Transient processes were analyzed in the automatic control system of the vibroactive forces electrodynamic compensator. Active vibration isolation system was considered, where a pneumatic spring based on the rubber-cord shell and the vibroactive forces electrodynamic compensator with a hydraulic inertial motion transducer were combined in a single construct. The paper shows that to ensure high efficiency of the vibration isolation, the gain in the electrodynamic compensator control circuit should be sufficiently large, but this leads to an increase in the transient process and the oscillation period duration. The proportional-integral controller could be introduced to reduce the oscillation index in the control system. However, the inertial mass oscillation center is shifting in the electrodynamic compensator in this case, which could lead to losses in its performance. An approach to solving this problem is proposed using the mechanism of averaging the measured current in the control coil and subtracting it from the current value, which makes it possible to eliminate the inertial mass shift while maintaining the transient process short duration, when a proportional-integral controller is included in the control circuit. It is shown that reducing the transient process period due to inclusion of the proportional-integral controller in the control circuit significantly increases the vibration isolation efficiency in the vibroactive forces non-stationary mode, for example, in the start-stop mode.

Research and optimization design of dual-frequency vibration isolation system for helicopter reducer

Dynamic antiresonance vibration isolation technology is widely used in the vibration reduction system of helicopters, because its simple structure and high vibration isolation efficiency. In this study, a dual-frequency vibration isolation system with two anti-resonant frequencies has been established, which can adapt to the vibration characteristics of two main vibration frequencies caused by the variable speed of the new high-speed helicopter. The theoretical equation and transmissibility of the dual-frequency vibration isolation system are derived, and the variation law of the weight and other relevant parameters on the vibration isolation performance is explored. The accuracy of the theoretical results is verified by model tests. According to the installation form of the helicopter reducer, the structure of the dual-frequency vibration isolation system is preliminarily optimized, which provides technical support for the design of the vibration isolator of the helicopter with variable speed.

Design of nonlinear metal rubber isolator subjected to random vibration

In this paper, a strategy to analyze the response of nonlinear metal rubber (MR) isolator under random vibration is proposed. And the stiffness and damping coefficient of MR isolator are designed to achieve broadband vibration efficient isolation. Firstly, the dynamic model of isolator is established considering the nonlinear characteristics of MR, and the effects of parameters on transmissibility are analyzed. Then, the Harmonic Balance Method is adopted for the numerically study, and the response of a nonlinear MR isolator subjected to random vibration is investigated. Next, the influence of parameters on the random vibration response are analyzed, and a design procedure is proposed to optimize the parameters for better vibration isolation efficiency by genetic algorithm. Finally, random vibration experiments are conducted for verification. It is demonstrated that the use of a numerical model in design procedure has been validated against experimental results, which can be extended to design other isolators with nonlinear stiffness and achieve a refined understanding of the nonlinear phenomena to a certain extent. Based on the proposed numerical model and design procedure, the obtained MR isolator has achieved high vibration isolation efficiency around 80% in three directions.

Isolation Effect of P-Wave By Double-Layer Wave Impeding Barrier in Unsaturated Foundations

Wave impeding block (WIB) barriers are often used to reduce vibration from different sources, but traditional vibration isolation of WIB has been limited to homogeneous materials and single-phase elastic or two-phase saturated foundations by many researchers. In fact, soils in nature are usually tri-phase unsaturated materials, and the propagation characteristics of elastic waves in unsaturated medium are completely different from those in single-phase elastic medium or two-phase saturated porous medium. In addition, the conventional WIB barrier has better vibration isolation only at low frequencies. Therefore, this paper improves the vibration isolation of the WIB by double-layer WIB with the same thickness on the basis of traditional WIB. Based on the wave theory of unsaturated porous media and elastic media, and according to the Helmholtz principle, we can obtain the solution of surface vertical displacement after setting double-layer WIB in unsaturated foundation, and then the isolation effect of double-layer WIB in unsaturated foundation under [Formula: see text]-wave incidence is investigated. The wave impedance ratio at the interface between WIB and unsaturated soil and wave impedance ratio at the interfaces among the layers of WIB is first analyzed on the vibration isolation effect of double-layer WIB, and the wave impedance ratio corresponding to the optimal vibration isolation effect of WIB barrier is achieved. Then the key factors such as incidence angle, incidence frequency, saturation, thickness, and burial depth of the double-layer WIB are evaluated on its vibration isolation properties. Finally, the isolation effects of single-layer homogeneous WIB and double-layer non-homogeneous WIB with the same thickness are compared. For the same thickness isolation barrier, the vibration isolation efficiency of double-layer WIB is 42.73% higher than single-layer at the incidence angle of [Formula: see text]–[Formula: see text]. The double-layer WIB has better isolation effect at low, medium and high frequencies than single-layer WIB.

The research about application of quasi-zero stiffness vibration isolation technology in a large vehicle-mounted optic-electronic equipment

The large vehicle-borne optic-electronic tracking equipment has the characteristics of heavy inertia, complex road condition and wide vibration spectrum. In order to solve the problem of passive broadband vibration isolation for vehicle-mounted moving platform optic-electronic equipment, a combined quasi-zero stiffness vibration isolation scheme is proposed. The vibration of the engine, generator, water cooler and the remaining vibration amplitude, frequency and Yaw of the road after passing the self-vibration isolation system of the vehicle are collected and confirmed by means of calculation simulation and field test. At the same time, the effective load of photoelectric equipment is analyzed by frequency sweeping test, and the corresponding multi-mode frequency points are obtained. According to the characteristics of the special equipment, a quasi-zero-stiffness vibration isolation system is designed to suppress the wide-frequency and high-amplitude vibration and Yaw caused by vehicle-borne vibration source, ground vibration source and resonance point of the equipment, the foundation stability of load equipment under dynamic condition is realized, which provides a condition for solving the problem of high precision and stability tracking which is greatly influenced by vibration. The vibration isolation system can realize the vibration isolation efficiency of 90% in the range of 20 Hz to 2000 Hz under the condition of 60 Km/h three-class highway with 1.5 t photoelectric load, and restrain the deflection caused by unbalance torque and vibration source offset effectively. It can be concluded that the quasi-zero stiffness vibration reduction and isolation combination design can effectively suppress the vibration of the large-scale vehicle-mounted optic-electronic equipment under the condition of moving platform.

Analysis and Experimental Study of Excitation Force Transfer Path of Optical Satellite Refrigeration Module

When the problem of the reaction force under the receiver structure is complicated, the existing force-based transfer path analysis method is not suitable for its analysis. Therefore, an improved reaction force transfer path analysis method is proposed in this paper. In the transfer path analysis method based on the modal superposition method, the penalty function method is introduced, and the path contribution of the receiving end reaction force is evaluated by analyzing the displacement response of the connection between the transfer path and the receiving end. A simulation analysis of a satellite refrigeration module vibration isolation device designed by the research group identified the main factors affecting the vibration isolation efficiency of the vibration isolation ring, and provided guidance for subsequent further optimization. The device was tested and analyzed by building an experimental platform, and the obtained simulation data fit well with the test data. These conclusions further show that the proposed analysis method can more accurately and conveniently analyze the path contribution of the receiving end reaction force under specific working conditions. This method is suitable for analyzing the transfer path of the reaction force at the receiving end in the design stage.

Улучшение условий труда персонала пневматического ковочного молота по вибрационным параметрам

Forging and stamping production is the basis of the procurement base of mechanical engineering. A variety of forging and pressing equipment ensures the production of most of the stampings and forgings used at the blank production stage. Working conditions in the forging shops are traditionally far from perfect. The main reasons for this are the number of unfavorable factors present in the forging shops, the main ones being noise and vibration, which most negatively affect the maintenance personnel. The article focuses its main attention on the evaluation of the vibrational activity of forging and pressing machines. It is indicated that vibration-isolating installations for stamping and forging hammers were developed. There are no such installations for pneumatic forging hammers. The results are given concerning the study on the design of a vibration-isolating installation for pneumatic forging hammers as a type of vibration-active equipment. To reduce the vertical vibrations of this equipment, multi-leaf springs are used, which efficiently reduce vibrations and have a long service life. Performance of the vibration isolating structure is ensured by installing a hammer on an intermediate frame supported by the springs installed in the foundation pit. The frame eliminates the rocking of the hammer and provides a uniform load on the spring. Parametric analysis of the vibration isolation unit showed that when the stiffness of the shock absorbers used is changed, the vibration activity of the machine can be reduced. A vibration-isolating installation for a forging pneumatic hammer, designed to improve the working conditions of personnel, was developed and successfully tested in production. Thanks to this installation, the vibration activity of the machine was significantly reduced and brought into line with sanitary standards, which improved the working conditions of the blacksmith and his assistant. Efficiency of vibration isolation is not changing in all modes of the hammer operation. The developed design is recommended for wide implementation in forging shops to improve the vibration characteristics of the hammer and to provide the possibility of placing such machines near vibration-sensitive objects.

Study on the Application of Vibration Isolation by Using a Trench in Frame Structures

An isolation trench is a simple and effective method to isolate structural vibrations originating from sources of vibration other than earthquakes (machines, traffic, explosions, etc.); however, there is still not a conclusive depth of the isolation trench for frame structures. To investigate the isolation effect of a trench in the frame structure designed for ground vibration, both a field test and finite element analysis were conducted to analyze the reduced effect of the vibration. The vibration reduction analysis was based on the dynamic equation and wave theory. Considering the vibration control of an industrial plant frame, a soil-trench-building finite element model was built to analyze the vibration characteristics of the floor before and after the open isolation trench structure was used. According to the model, a dynamic test was carried out on the frame structure to assess the effect of the vibration reduction by introducing the trench. The results showed that the depth of the trench was the dominating factor in vibration isolation. When the depth of the trench reached 1~1.3 times the wavelength of the Rayleigh wave, the damping effect was the strongest. the width of the trench has little effect on the vibration isolation efficiency, and the trench must be maintained at a certain distance from the building to ensure the vibration damping efficiency. The vibration of each floor was obviously reduced after the trench was built. The vibration damping effect of the trench was significant.

Horizontal hollow pipes used as vibration isolation barriers: Numerical modelling and design optimization

Open trenches are one of the most popular vibration isolation techniques used to reduce the transmission of ground vibrations. Despite several advantages of this systems for isolating ground vibrations, the major drawback is the geotechnical instability of the trenches. To solve this issue, the author have created a novel approach that involves filling the open trenches with hollow pipes in specific pattern. This is a novel method for mitigating ground vibrations by burying hollow pipes horizontally. Through the use of three-dimensional (3D) finite-element modeling, the effectiveness of such hollow pipes in decreasing ground vibrations generated by harmonic stress excitation on the ground surface was investigated. Compared to open trench barriers and in-filled trench, these pipe assemblages have been demonstrated to be highly successful in reducing ground vibration transmission while addressing issues of instability and enhancing vibration isolation efficiency. In PLAXIS3D, a dynamic numerical model is developed, and the results are validated against available solutions. Then, an optimized design technique for wave barriers is developed, and explore the effect of layered soil on vibration isolation effectiveness of hollow pipes.

Sensitivity analysis regarding the structural parameters of the inner cylinder embedded fluidlastic base

The inner cylinder embedded fluidlastic base is a device installed on the main reduction transmission channel of the helicopter to isolate the vibration load of the fuselage from the rotor system, whose vibration isolation efficiency is quite high. Compared with the traditional combined fluidlatic isolator, the fluidlastic base has higher reliability and safety in engineering application prospects. In this paper, taking a UAV as the research object, the structure of the fluidlastic base is preliminarily designed in light of structure space of its main reduction system, and its dynamic equation is established according to the working principle of the fluidlastic base to deduce the force transmission rate expression. Finally, taking the minimum force transmission rate as the research target, sensitivity analysis of the structural parameters is carried out for the fluidlastic base, which provides an optimization method for the optimal design of the vibration isolator.

Numerical evaluation of tire chips–filled trench barriers for effective vibration isolation

Ground vibrations induced by man-made sources like vibrating machinery, vehicular movement, traffic, construction activities involving pile driving, blasting, dynamic compaction, etc., are rising rapidly and may disrupt nearby sensitive equipment, distress, and damage sub-structures. Therefore, vibration isolation is necessary to mitigate ground-borne vibrations with suitable techniques in the present-day context. Trench barriers are one of the most efficient techniques when the other isolation techniques are inefficient at the source. Although the open trench barriers are the most efficient, their stability is still a significant concern. Hence, these trenches are generally filled with suitable absorbing materials such as sawdust, geofoam, and concrete. The present study has attempted to explore the feasibility of using shredded tire chips as an infill material by evaluating their performance using the finite element method. The performance of tire chips–filled trench barriers predicted using FE analysis is also compared with the performance of other common infill materials such as sawdust and geofoam. Numerical studies show that the vibration isolation efficiency and their performance are highly sensitive to the shear wave velocity of the soil and infill material density for infill trenches. The key findings of the study suggest that shredded tire chips can also be used as an infill material in trenches for reducing ground-borne vibrations, and its performance is comparable with geofoam-filled trenches.

Optimization of Dual-Mass Flywheel Parameters Based on a Multicondition Simulation Test

A dual-mass flywheel is an important part of an automobile transmission system whose function is to ensure the smooth transmission of engine power to a gearbox. Vehicle vibration and noise are major indicators of vehicle comfort, while dual-mass flywheel technology can preferably solve the comfort problem. Based on the created torsional vibration model, this paper describes the testing of the torsional characteristics under various conditions with an LMS AMESim simulation. The results show that the noise in the cab is fundamentally below 60 dB. The computational formula for the angular stiffness of an arc coil spring is derived, and then the spring angular stiffness is optimized with arithmetic averaging, which reveals an adjusted angular stiffness of 12.8 Nm/°. Additionally, the requirement for the angular acceleration of the WOT input shaft (i.e., being less than 500 rad/s2) is satisfied for various gears. The test results show that the double-mass flywheel can attain a vibration isolation efficiency of around 85%, which more effectively reduces the transmission vibration and noise and improves the vehicle comfort.

Finite-Element Simulation of a Resonant Frequency-Tunable Vibration Isolator Based on Shape Memory Alloy Wire

BackgroundThe resonant-frequency-tunable vibration isolator based on Shape Memory Alloys (SMAs) combines the priority of passive and active vibration isolators, expands its engineering application, and improves the efficiency of vibration isolation. However, the special characteristics of SMAs and the complexity of the resonant-frequency-tunable vibration isolator result in the difficulty in finite-element analysis.MethodsThis article employs the ABAQUS subroutine and presents the finite-element analysis for this resonant-frequency-tunable vibration isolator, which simulates the thermomechanical responses of SMA wires and the mechanical behaviors of the vibration isolator.ResultsThe pseudoelasticity characteristics of SMA wires were simulated and validated. The mechanical characteristics of the vibration isolator, such as the temperatures, martensitic volume fractions, displacements, and equivalent stresses, were obtained and verified.ConclusionsThe results show that the finite-element analysis method presented is appropriate for simulating mechanical behaviors of the resonant-frequency-tunable vibration isolator. The analysis results reveal in detail the mechanical characteristics of the vibration isolator.

Study of the multi-excitation decoupling optimization method for the integrated structure of a high-resolution optical satellite

In this paper, the sensitive frequency band for distortion and blurring phenomena of the in-orbit satellite is studied and the results are supplements for existing studies and can provide an important reference for the study of micro-vibration. To contain the large-amplitude and micro-vibration excitation response in this sensitive frequency band, a multi-excitation decoupling optimization method is proposed for the integrated structure of high-resolution optical satellites. First, the equivalent dynamics models of the satellite with and without an vibration isolator are established. By deriving the functional relationship between satellite bus stiffness, vibration isolator stiffness, and vibration isolation efficiency, the design objectives can be decoupled and assigned to the vibration isolator and satellite bus in a more cost-effective way, respectively, while maintaining a low computation volume of the multi-objective and multi-variable system optimization. Then, the satellite system is optimized with the objectives of minimizing the large-amplitude vibration response in the launch phase and the micro-vibration response in the orbital operation phase using the NSGA-II genetic algorithm. Finally, the design is verified by ground experiments that it can fully achieve required technical parameters under multiple vibration excitations. This method has certain reference value for the design of complex structural systems of high-resolution satellites.