Vibration Isolation Design Research Articles

Vibration Isolation Design for the Micro-X Rocket Payload

Micro-X is a NASA-funded, sounding rocket-borne X-ray imaging spectrometer that will allow high precision measurements of velocity structure, ionization state and elemental composition of extended astrophysical systems. One of the biggest challenges in payload design is to maintain the temperature of the detectors during launch. There are several vibration damping stages to prevent energy transmission from the rocket skin to the detector stage, which causes heating during launch. Each stage should be more rigid than the outer stages to achieve vibrational isolation. We describe a major design effort to tune the resonance frequencies of these vibration isolation stages to reduce heating problems prior to the projected launch in the summer of 2014.

Dynamics Analysis and Vibration Isolation Design of Shared Foundation on Marine Turbo Generator Set

Considering the ship's limited space, high speed and miniaturization have been design directions in marine turbo generator set. The shared foundation with steel plate welding is designed to support the marine turbo generator set. Stiffness and dynamic characteristic of the shared foundation will directly affect the stable operation of the turbo generator set. The paper established the dynamics analysis model for the shared frame of marine turbo generator set according to the 'Lumped Mass Method'. Taking account of the frequency-domain analysis operability, the operational modal analysis and dynamical response on foundation were carried out by Virtual Lab. Based on these results; the intensity and location of exciting force were ascertained. And then, we designed the shared foundation vibration isolation system, and analyzed the characteristics of the vibration isolation mounting. The result shows that the vibration isolation system can minimize output force transmissibility and reduce the effect of the marine turbo generator set vibration.

Experimental Study on Fatigue of Metal Rubber Vibration Isolator under Pulsating Cyclic Stress

Metal Rubber(MR) vibration isolator is a new type of isolator developed to overcome the fatal aging phenomenon of current rubber isolator. It has broad practical application in the military, such as aerospace. In this paper, the fatigue life experiment is conducted to MR vibration isolator, and resonant frequency and resonant accelerate transmissibility are chose as degradation parameters. It’s found that MR vibration isolator possesses jump phenomenon; resonant frequency and resonant transmissibility increase quickly to the maximum, then attenuate slowly with the increasing number of vibration. This provides fundamental basis for the design and application research of MR vibration isolators.

Vibration Isolator Design for Space Application Based on Multiobjective Optimization Method

A multiobjective optimization based vibration isolator design for space application is described. It is common to use passive isolator and isolate the platform noise in space applications. The design of a passive isolator involves a trade-off between the resonant peak reduction and the high frequency attenuation. The equation of motion and transfer function model for single-stage and two-stage connector model is derived by using basic principle. The multiobjective optimization model is proposed, where the design variables are the damping coefficients and stiffness coefficients, the objective functions are the resonant peak reduction and the high frequency attenuation, and the constraints are the natural frequency of the connector. The multiobjective optimization problems for the design of the passive isolator are solved by using the multiobjective evolutionary algorithm based on decomposition (MOEA/D). The Pareto front obtained can provide multiple candidate solutions for the designer. The method is effective for the design process of the passive isolator.

An Approximate Formula to Calculate the Restoring and Damping Forces of an Air Spring With a Small Pipe

This paper proposes a simple expression for calculating the restoring and damping forces of an air spring equipped with a small pipe. Air springs are commonly used in railway vehicles, automobiles, and various vibration isolators. The air spring discussed in this study consists of two tanks connected by a long pipe. Using a pipe instead of an orifice enables flexibility in the arrangement of the two tanks. In addition, this makes it possible to manufacture a thin air spring. A vertical translational oscillating system, which consists of a single mass supported by this type of air spring, looks like a single-degree-of-freedom (SDOF) system. However, it may have two resonance points. In this paper, we propose a vibratory model of a system supported by the air spring. With the proposed model it is possible to correctly reproduce the two resonance points of a system consisting of a single mass supported by this type of air spring. In our analysis, assuming that the vibration amplitude is small and the flow through the pipe is laminar, we derive the spring constant and damping coefficient of an air spring subjected to a simple harmonic motion. Then, we calculate the frequency response curves for the system and compare the calculated results with the experimental values. According to the experiment, there is a remarkable amplitude dependency in this type of air spring, so the frequency response curves for the system change with the magnitude of the input amplitude. It becomes clear that the calculation results are in agreement with the limit case when the input amplitude approaches zero. We use a commercially available air spring in this experiment. Our study is useful in the design of thin air spring vibration isolators for isolating small vibrations.

Evaluation of transmissibility for a class of nonlinear passive vibration isolators

In this study, the concept of Output Frequency Response Functions (OFRFs) is applied to represent the transmissibility of nonlinear isolators in frequency domain. With the OFRFs estimated from numerical simulation responses, an explicit analytical relationship between the transmissibility and the nonlinear characteristic parameters is derived for a wide class of nonlinear isolators that have nonlinear anti-symmetric damping characteristics and a comprehensive pattern about how the nonlinear damping characteristic parameters might affect the force and displacement transmissibility is built for the vibration isolators. The results reveal that it is reasonable to analyze the force and displacement transmissibility of the nonlinear isolators by simply investigating the fundamental harmonic components of the force and displacement outputs of the nonlinear isolators, and the introduction of a nonlinear anti-symmetric damping into vibration isolators can significantly suppress both the force and displacement transmissibility over the resonant frequency region, but has almost no effect on the transmissibility at non-resonant regions. These conclusions are of significant importance in the analysis and design of the nonlinear vibration isolators with nonlinear anti-symmetric damping.

Smooth Vibrotactile Flow Generation Using Two Piezoelectric Actuators.

This paper proposes a method for generating a smooth directional vibrotactile flow on a thin plate. While actuating two piezoelectric actuators spatially across the plate, temporal sweeping of the input excitation frequency from zero to the first mode of the resonance frequency can smooth the perceived directional vibrotactile flow, as compared to a vibrotactile flow generated by conventional apparent tactile movement and phantom sensation methods. In order to ascertain important factors in the excitation pattern, a user study was conducted for three factors (amplitude (constant versus modulated), frequency (constant versus swept), and ending shape (sharp versus smooth)). The results showed that frequency sweeping in addition to amplitude modulation and smooth ending were the most important factors in smoothing vibrotactile flows. Moreover, an excitation signal with a smooth ending shape was important for generating nonspiky flows at the midpoint. In this study, a vibration isolation design is also proposed in order to substantially decrease the transmission of the actuator vibration to the mockup housing. As such, it is expected that the proposed vibrotactile flow generation method and vibration isolation design may be useful in applications including generating directional information in navigation maps or for identifying callers in mobile devices.

Low-Frequency Shaking of the Construction Machine Cab and Design of Vibration Isolators for Protecting

Focusing on low-frequency shaking of the construction machine cab, the article analyzes reasons of the shaking and shows several improved isolator designs to reduce the effect of shaking on drivers’ comfort. Firstly according to previous 4 modes below 26 Hz from the finite element analysis of an excavator cab with 6 cab mounts, reasons for low-frequency shaking are analyzed. Then two improved measures of isolator designs for keeping the shaking small effectively are considered. Static analysis on one silicone-oil-sealed-type rubber mount, which can improve drivers’ comfort effectively according to practical application, is done. Besides, perfect setting approaches of isolators can greatly alleviate the cab shaking, which is confirmed by finite element modal analysis of the excavator cab, the first natural frequency of cab increased to 15.55Hz from 6.91Hz.

Structure Design and Finite Element Analysis of Airborne Equipment Integrated Mounting Shelf

Abstract. This paper introduces an architecture design of airborne equipment integrated mounting shelf, including constitution of mounting shelf, design method, vibration isolation design,finite element analysis and calculation, etc. Mounting interface between mounting shelf and airborne aircraft is complicated; weight is limited; load on mounting shelf is big and mechanically severe environment must be met. Through dedicated design and simulation analysis, this product has passed each item of airborne environment tests and equipped in military.

Study of the effects of cubic nonlinear damping on vibration isolations using Harmonic Balance Method

In the present study, Harmonic Balance Method (HBM) is applied to investigate the performance of passive vibration isolators with cubic nonlinear damping. The results reveal that introducing either cubic nonlinear damping or linear damping could significantly reduce both the displacement transmissibility and the force transmissibility of the isolators over the resonance region. However, at the non-resonance region where frequency is lower than the resonant frequency, both the linear damping and the cubic nonlinear damping have almost no effect on the isolators. At the non-resonance region with higher frequency, increasing the linear damping has almost no effects on the displacement transmissibility but could raise the force transmissibility. In addition, the influence of the cubic nonlinear damping on the isolators is dependent on the type of the disturbing force. If the strength of the disturbing force is constant and independent of the excitation frequency, then the effect of cubic nonlinear damping on both the force and displacement transmissibility would be negligible. But, when the strength of the disturbing force is dependent of the excitation frequency, increasing the cubic nonlinear damping could slightly reduce the relative displacement transmissibility and increase the absolute displacement transmissibility but could significantly increase the force transmissibility. These conclusions are of significant importance in the analysis and design of nonlinear passive vibration isolators.

A magnetorheological fluid embedded pneumatic vibration isolator allowing independentlyadjustable stiffness and damping

A magnetorheological (MR) fluid embedded pneumatic vibration isolator (MrEPI) withhybrid and compact connection of pneumatic spring and MR damping elements is proposedin this study. The proposed MrEPI system allows independent nonlinear stiffness anddamping control with considerable maneuverable ranges. Meanwhile, it allows convenientswitching between different passive and active vibration control modes, thus providingmore flexibility and versatility in applications. To demonstrate the advantageous dynamicperformance of the MrEPI, a nonlinear non-dimensional dynamic model is developed withfull consideration of the nonlinear elements involved. A systematic analysis is thereforeconducted which can clearly reveal the influence on system output performance caused byeach physically important parameter and provide a useful insight into the analysisand design of nonlinear vibration isolators with pneumatic and MR elements.

Application of Lead Rubber Bearing in Curved Continuous Bridge

Based on the general FEA program, the bidirectional nonlinear behavior of lead rubber bearing is taken into account by using two orthogonal nonlinear spring elements. Considering the effect of radius of curvature, lead diameter and dissimilar seismic motions, dimensional FEA model of seismically isolated curved continuous bridge is established. And the seismic energy response analyses for seismically isolated curved continuous bridge are carried out under the three-dimensional seismic motions. So, some meaningful references are provided for the design of vibration absorption and isolation of the curved beam bridge in this paper.

The influence of blocking mass parameters on the vibration isolation performance of a power cabin

Rigid blocking masses are located in the typical base structure of a power cabin based on the impedance mismatch principle. By combining the acoustic-structural coupling method and statistical energy analysis, the full-band vibration and sound radiation reduction effect of vibration isolation masses located in a base structure was researched. The influence of the blocking mass’ cross-section size and shape parameters and the layout location of the base isolation performance was discussed. Furthermore, the effectiveness of rigid vibration isolation design of the base structure was validated. The results show that the medium and high frequency vibration and sound radiation of a power cabin are effectively reduced by a blocking mass. Concerning weight increment and section requirement, suitably increasing the blocking mass size and section height and reducing section width can result in an efficiency-cost ratio.

Optimization of passive vibration isolators mechanical characteristics

The contribution of optimization has been essential to the more recent developments in design of new mechanical structures and materials. The objective of this work is to apply the models of material and structural optimization to the design of passive vibration isolators. A computational tool to identify the optimal viscoelastic characteristics of a nonlinear one-dimensional isolator was developed. The cost functional involves the minimization of a weighted average of the maximum transient and steady state response amplitudes for a set of predefined dynamic loads. The optimal isolator behaviour is obtained by a simulated annealing method. The solutions obtained are analyzed and discussed concerning their dependence on the applied forces and objective function selection. The results obtained can facilitate the design of elastomeric materials with improved behaviour in terms of dynamic stiffness for passive vibration control.

The Transmissibility of Vibration Isolators With a Nonlinear Antisymmetric Damping Characteristic

In the present study, the concept of the output frequency response function, recently proposed by the authors, is applied to theoretically investigate the force transmissibility of single degree of freedom (SDOF) passive vibration isolators with a nonlinear antisymmetric damping characteristic. The results reveal that a nonlinear antisymmetric damping characteristic has almost no effect on the transmissibility of SDOF vibration isolators over the ranges of frequencies, which are much lower or higher than the isolator’s resonance frequency. On the other hand, the introduction of a nonlinear antisymmetric damping can significantly reduce the transmissibility of the vibration isolator over the resonance frequency region. The results indicate that nonlinear vibration isolators with an antisymmetric damping characteristic have great potential to overcome the dilemma encountered in the design of passive linear vibration isolators, that is, increasing the level of damping to reduce the transmissibility at the resonance could increase the transmissibility over the range of higher frequencies. These important theoretical conclusions are then verified by simulation studies.

A simplified 3-D human body–seat interaction model and its applications to the vibration isolation design of high-speed marine craft

High-speed boats experience a harsh vibration environment and human response to this environment is of increasing interest to naval architects who wish to mitigate the effects of vibration and shocks. Based on published experiment data, a three-dimensional human body model with one degree-of-freedom in each direction is established. This model is combined with a simple seat model to construct a simplified 3-D human body–seat interaction model for naval architects to investigate the integrated interaction system when subjected to ship motions. The governing equations describing the dynamics of the human body–seat interactions are formulated and their theoretical solutions are derived. This model, in association with the experimental data recorded on board a high-speed marine craft, is used to study seat isolation system designs. The spring coefficient of the seat isolation system is chosen to avoid any resonance of the human–seat interaction system excited by sea waves. The damping coefficient of the seat isolation system is determined to attenuate motions at the most common excitation frequencies. The designed system is further checked by considering its response to an individual slam impact where the designed system is compared with typical existing seats to illustrate the potential advantages of the proposed approach. In addition the designed seat is compared with existing seats excited by actual boat loads. The study provides a simplified, effective approach for high-speed craft seat design in reducing the shock and vibration level experienced by the crew.

Study of Whole-spacecraft Vibration Isolators Based on Reliability Method

The traditional payload attaching fitting (PAF) does not provide any vibration isolation, because of its large stiffness. Whole-spacecraft vibration isolation is a direct and effective approach to assure the successful launching and orbit insertion of a spacecraft. In view of the problems of stiffness and vibration isolation design, for which the designers care most, the study of whole-spacecraft vibration isolator (WSVI) consists of two parts. In the first part, the stiffness feature of the WSVI is studied with reliability analysis and experimental data. In the second part, the problems induced by stiffness feature are discussed. The simulated and experimental data show that the transmissibility, which is coupled with stiffness, can be reduced by attaching the vibration isolator between the spacecraft and the launch vehicle.

Design and Analysis of Shock and Random Vibration Isolation of Operating Hard Disk Drive in Harsh Environment

An effective vibration isolation system is important for hard disk drives (HDD) used in a harsh mechanical environment. This paper describes how to design, simulate, test and evaluate vibration isolation systems for operating HDD subjected to severe shock and random vibrations based on military specifications MIL-STD-810E. The well-defined evaluation criteria proposed in this paper can be used to effectively assess the performance of HDD vibration isolation system. Design concepts on how to achieve satisfactory shock and vibration isolation for HDD are described. The concepts are tested and further enhanced by the two design case studies presented here. It is shown that an effective vibration isolation system, that will allow a HDD to operate well when subjected to severe shock and random vibration, is feasible.

Design and Analysis of Shock and Random Vibration Isolation of Operating Hard Disk Drive in Harsh Environment

An effective vibration isolation system is important for hard disk drives (HDD) used in a harsh mechanical environment. This paper describes how to design, simulate, test and evaluate vibration isolation systems for operating HDD subjected to severe shock and random vibrations based on military specifications MIL-STD-810E. The well-defined evaluation criteria proposed in this paper can be used to effectively assess the performance of HDD vibration isolation system. Design concepts on how to achieve satisfactory shock and vibration isolation for HDD are described. The concepts are tested and further enhanced by the two design case studies presented here. It is shown that an effective vibration isolation system, that will allow a HDD to operate well when subjected to severe shock and random vibration, is feasible.

Optimisation of building vibration isolation by means of numerical methods

Ground‐borne vibrations pose a steadily increasing environmental problem in densely populated areas of large cities. Although not the cheapest, the application of resilient elements in the construction of new buildings is an effective and viable method. Obviously, experimentation with parameters and placement of the isolators is not possible in this case. Therefore, a careful and watchful optimization of the static and dynamic characteristics of the supporting elements is a must. The proposed paper gives an overview of the vibration isolation design and reports on the expected effect of some basic design versions of a typical multi‐storey building. Standard structural finite element method is used as a basic design tool, but a number of vibro‐acoustic aspects are also considered and treated. Experimental results as well as comparisons of measurements and predictions will be reported too.