Optimal Design and Simulation of Vibrational Isolation Systems

1985 ◽  
Vol 107 (2) ◽  
pp. 271-276 ◽  
Author(s):  
C. E. Spiekermann ◽  
C. J. Radcliffe ◽  
E. D. Goodman
Keyword(s):  
Rigid Body ◽  
Penalty Function ◽  
Vibration Isolation ◽  
Natural Frequencies ◽  
Design Tool ◽  
Function Optimization ◽  
Mode Shapes ◽  
Design Parameters ◽  
Frequency Range ◽  
Isolation System

Vibration isolation of a rigid body on compliant mounts has many engineering applications. An analysis for solving these problems using a rigid body simulation and a penalty function optimization is discussed. The simulation is used to calculate natural frequencies and mode shapes, which are a function of the mount design parameters. Laboratory testing results are presented which verify the accuracy of the simulation. The optimization procedure penalizes natural frequencies in an undesirable frequency range and also large design changes. This penalty function is minimized by changing the mount design paramters consisting of the location, stiffness, and/or orientation. The result is a set of design parameters defining a vibration isolation system with natural frequencies moved away from the center of the undesirable frequency range. An interactive computer program was written which allows the engineer to use this technique as a design tool.

Modal Analysis of Magnetic Resonance Imaging (MRI) Scanner Support Structure

2018 ◽  
Author(s):  
Geneviève Rodrigue ◽  
Chris K. Mechefske
Keyword(s):  
Modal Analysis ◽  
Vibration Isolation ◽  
Natural Frequencies ◽  
Design Tool ◽  
Mode Shapes ◽  
Resonance Imaging ◽  
Support Structure ◽  
Analysis And Design ◽  
Passive Vibration Isolation ◽  
Magnetic Resonance Imaging Mri

Experimental and computational modal analysis has been completed as part of a larger project with the ultimate goal of understanding MRI vibration and implementing passive vibration isolation in the MRI machine support structure. The specific purpose of the modal analysis is to extract natural frequencies (eigenvalues) and mode shapes (eigenvectors) of the MRI support structure in order to validate the computational model of the base against the experimental results so that the former may be used as an analysis and design tool. From the model, the resonance points of the MRI support structure are determined within the expected frequency ranges of excitation.

A Variable Stiffness Vibration Isolation System Based on Magneto-Rheological Elastomer

2012 ◽  
Vol 452-453 ◽  
pp. 659-662
Author(s):  
Wei Wang ◽  
Yi Min Deng
Keyword(s):  
Shear Modulus ◽  
Vibration Isolation ◽  
Variable Stiffness ◽  
Control Area ◽  
Frequency Range ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Vibration Isolators ◽  
Magneto Rheological ◽  
Conventional Type

Vibration isolation is a most widely used vibration protection method.The stiffness of vibration isolators in existing conventional type of vibration isolation system is usually of fixed value. This limits the system in exhibiting its vibration isolation effect in that, it has poor results for lower frequency vibration, especially for resonance frequency. Magneto-rheological elastomer is a new branch of Magneto-rheological materials. It’s an intelligent materials in that it’s shear modulus can be controlled by a magnetic field. It has wide application prospects in the vibration control area. This paper proposes using adjustable stiffness of magneto-rheological elastomer vibration isolation in vibration isolation system. By changing the current of vibration isolators coil to control the shear modulus of magneto-rheological elastomer, it can adjust the stiffness of the isolation system, making the system obtain wider vibration isolation frequency range. By exploying SimuLink software to analyze the vibration isolation system, it is found that such a design is effective and applicable.

Split Vibration Modes in Acoustically-Coupled Disk Stacks

1995 ◽  
Author(s):  
Jung-Ge Tseng ◽  
Jonathan Wickert
Keyword(s):  
Natural Frequencies ◽  
Three Dimensional ◽  
System Level ◽  
Thin Plates ◽  
Mode Shapes ◽  
Design Parameters ◽  
Phase System ◽  
Acoustic Coupling ◽  
Annular Plates ◽  
Vibration Model

Abstract Vibration of an array of stacked annular plates, in which adjacent plates couple weakly through an acoustic layer, is investigated through experimental and theoretical methods. Such acoustic coupling manifests itself through split natural frequencies, beating in the time responses of adjacent or separated plates, and system-level modes in which plates in the array vibrate in- or out-of-phase at closely-spaced frequencies. Laboratory measurements, including a technique in which the frequency response function of all in-phase modes but no out-of-phase modes, or visa versa, is measured, demonstrate the contribution of coupling to the natural frequency spectrum, and identify the combinations of design parameters for which it is important. For the lower modes of primary interest here, the natural frequencies of the out-of-phase system modes decrease as the air layer becomes thinner, while those of the in-phase mode remain sensibly constant at the in vacuo values. A vibration model comprising N classical thin plates that couple through the three-dimensional acoustic fields established in the annular cavities between plates is developed, and its results are compared with measurements of the natural frequencies and mode shapes.

Mechanical Behavior of an Electrostatically Actuated Microplate

2003 ◽  
Author(s):  
Xiaopeng Zhao ◽  
Eihab M. Abdel-Rahman ◽  
Ali H. Nayfeh
Keyword(s):  
Differential Equations ◽  
Natural Frequencies ◽  
Finite Dimension ◽  
Equations Of Motion ◽  
Galerkin Approximation ◽  
Mode Shapes ◽  
Design Parameters ◽  
Electrostatically Actuated ◽  
Linear Eigenvalue Problem ◽  
Electrically Actuated

We present a nonlinear model of electrically actuated microplates. The model accounts for the nonlinearity in the electric forcing as well as mid-plane stretching of the plate. We use a Galerkin approximation to reduce the partial-differential equations of motion to a finite-dimension system of nonlinearly coupled second-order ordinary-differential equations. We find the deflection of the microplate under DC voltage and study the pull-in phenomenon. The natural frequencies and mode shapes are then obtained around the deflected position of the microplate by solving the linear eigenvalue problem. The effect of various design parameters on both the static response and the dynamic characteristics are studied.

A Study of Active Vibration Isolation

1985 ◽  
Vol 107 (4) ◽  
pp. 392-397 ◽  
Author(s):  
N. Tanaka ◽  
Y. Kikushima
Keyword(s):  
Vibration Isolation ◽  
Control Method ◽  
Feedforward Control ◽  
Ground Vibration ◽  
Design Parameters ◽  
Isolation Method ◽  
Isolation System ◽  
Active Isolation ◽  
Active Vibration ◽  
Active Vibration Isolation

For the purpose of suppressing ground vibration produced by vibrating machines, such as forging hammers, press machines, etc., this paper presents an active vibration isolation method. Unlike conventional isolators, the active isolator proposed in this paper permits rigid support of the machines. First, the principle of the active isolation method is shown, and the system equations are derived. Secondly, the characteristics and the design parameters of the active isolation system are presented. Thirdly, from the point of view of the feedforward control method, the dynamic compensators are designed so as to sufficiently suppress the exciting force. Finally, an experiment is carried out to demonstrate that the active isolator is applicable for suppressing the ground vibration.

Passage Through Resonance in a Vibration Isolation System (Effects of Rate of Increasing the Voltage Applied to D.C. Motor)

2007 ◽  
Author(s):  
Tomohiko Tange ◽  
Ryo Kawana ◽  
Tetsuro Tokoyoda ◽  
Masatsugu Yoshizawa ◽  
Toshihiko Sugiura
Keyword(s):  
Rigid Body ◽  
Internal Resonance ◽  
Vibration Isolation ◽  
Transient Behavior ◽  
Degree Of Freedom ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Rotational Vibration ◽  
Three Degree Of Freedom ◽  
Driving Torque

This paper deals with transient nonlinear vibration of a rigid body suspended on a foundation by elastic springs and constrained in a plane. In such a three degree-of-freedom vibration isolation system, we assume that ‘2-1-1’ internal resonance exists between the vertical and horizontal vibrations of the rigid body and the rotational vibration about its center of gravity. Our main purpose is to examine theoretically the transient behavior passing through resonance under the condition that the D.C. motor directly drives the unbalanced rotor. Numerical simulation was carried out to clarify effects of rate of increasing V(t) on the peak amplitude of the vibration of the rigid body and on the driving torque of the D.C. motor. Moreover, experiment was conducted with a physical model of a three degree-of-freedom vibration isolation system, and the transient behavior passing through resonance was observed and compared with theoretical results in a typical case with internal resonance.

scholarly journals High Frequency Modal Testing of the Multiblade Packets Using a Noncontact Measurement and Excitation System

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
C. H. Liu ◽  
C. Zang ◽  
F. Li ◽  
E. P. Petrov
Keyword(s):  
High Frequency ◽  
Measurement Method ◽  
Natural Frequencies ◽  
Spectral Lines ◽  
Modal Testing ◽  
Frequency Resolution ◽  
Mode Shapes ◽  
Finite Model ◽  
Frequency Range ◽  
Noncontact Measurement

High cycle failure of blades and vanes caused by the vibration is one of the major causes reducing the lifetime of turbomachines. For multiblade packets, the failure may occur at vibrations with high frequencies that can reach up to tens of kHz. The experimental modal testing of blades is crucial for the validation of numerical models and for the optimization of turbomachine design. In this paper, the test rig and procedure for measurements of dynamic characteristics of lightweight multiblade packets in wide and high frequency ranges are developed. The measurements are based on a noncontact excitation and noncontact measurement method, which allows the determination of the modal characteristics of the packets with high accuracy in wide frequency ranges. The responses of the multiblade packets are measured using a Scanning Laser Doppler Vibrometry (SLDV), while vibrations are excited by the acoustic excitation technique. Modal tests of the blade packet comprising 18 vane blades connected by shrouds are performed. The measurements are performed within the high frequency range of 0–30 kHz, and the natural frequencies and mode shapes are obtained for first 97 modes. To capture the complex high frequency blade mode shapes, each blade in the packet is scanned over 25 reference points uniformly distributed over the blade concave surface. In order to obtain the high frequency resolution, the frequency range used for the measurements is split into several frequency intervals accordingly to the number of spectral lines available in the used data acquisition system, and for each such interval, the test is performed separately. The finite model of the packet is created, and the numerical modal analysis is performed to compare the calculated natural frequencies and mode shapes with the experimental measurements. The comparison shows the satisfactory with those from finite element analysis. It illustrates the measurement method described in this work is effective and reliable.

Multi-Junction, Multi-Branch Torsional Vibration in a Geared Rotating System

2000 ◽  
Author(s):  
Qing Ke Yuan ◽  
David Y. Yao
Keyword(s):  
Torsional Vibration ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Design Stage ◽  
Design Parameters ◽  
Analysis Program ◽  
Vibration System ◽  
Rotating System ◽  
Steel Rolling ◽  
Mining Machinery

Abstract A multi-junction, multi-branch torsional vibration system is often found in a geared rotating system. This is an important part in many types of machinery, such as mining machinery, petroleum machinery, steel rolling machinery and automobiles. If the design parameters of the system are improper, there will be serious torsional vibration, which will cause noticeable sound disturbances, severe shakings, and component fatigue problems. Analyzing and pre-estimating critical speeds or torsional natural frequencies and mode shapes of the vibration systems in the design stage is very important to avoid future disastrous and costly repairs of the machinery. In this paper, a radical and effective method for calculating natural frequencies and mode shapes of multi-junction, multi-branch torsional vibration systems, has been put forward, a program named MJBTVAP (Multi-Junction, multi-Branch Torsional Vibration Analysis Program) based on this method has been developed, actual problems have been solved.

A Parametrization Describing Blisk Airfoil Variations Referring to Modal Analysis

2017 ◽  
Author(s):  
Thomas Backhaus ◽  
Thomas Maywald ◽  
Sven Schrape ◽  
Matthias Voigt ◽  
Ronald Mailach
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Design Parameters ◽  
Surface Mesh ◽  
Main Mode ◽  
Airfoil Surface ◽  
Parametrization Method ◽  
Surface Meshes ◽  
Geometric Variation

This paper will present a way to capture the geometric blade by blade variations of a milled from solid blisk as well as the manufacturing scatter. Within this idea it is an essential task to digitize the relevant airfoil surface as good as possible to create a valid surface mesh as the base of the upcoming evaluation tasks. Since those huge surface meshes are not easy to handle and are even worse in getting quantified and easy interpretable results, it should be aimed for an easily accessible way of presenting the geometric variation. The presented idea uses a section based airfoil parametrization that is based on an extended NACA-airfoil structure to ensure the capturing of all occurring characteristic geometry variations. This Paper will show how this adapted parametrization method is suitable to outline all the geometric blade by blade variation and even more, refer those airfoil design parameters to modal analysis results such as the natural frequencies of the main mode shapes. This way, the dependencies between the modal and airfoil parameters will be proven.

The Transient Response of Structures Using Asymptotic Modal Analysis

1998 ◽  
Vol 65 (1) ◽  
pp. 258-265 ◽  
Author(s):  
R. R. Reynolds ◽  
E. H. Dowell
Keyword(s):  
Numerical Methods ◽  
Finite Elements ◽  
Modal Analysis ◽  
Impulse Response ◽  
Transient Response ◽  
High Frequency ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Frequency Range ◽  
Modal Solution

The transient response of a structure is predicted using an asymptotic modal approximation of the classical modal solution. The method is aimed at estimating the impulse response problem for high frequency regimes where typical numerical methods (e.g., finite elements) are impractical. As an example, the response of a thin elastic panel is modeled in a frequency range that includes a sufficient number of modes. Both impulsive and arbitrary forms of excitation are considered. It is shown that the asymptotic modal analysis yields an excellent estimate of both the local displacement near the excitation location and of the spatially averaged transient response of the panel for moderate time spans after the excitation is applied. Furthermore, as this approach does not require that the mode shapes or natural frequencies of the structure to be calculated, it is an extremely efficient technique.

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