Rubber Mounts Research Articles

TREATMENT OF FREQUENCY-DEPENDENT COMPLEX STIFFNESS FOR COMMERCIAL MULTI-BODY DYNAMIC ANALYSIS PROGRAMS1*

ABSTRACT Vibration isolation components such as rubber bushings or mounts are usually represented by the Voigt model for consideration of their dynamic characteristics in commercial multi-body dynamic analysis programs. The simple Voigt model, however, has limitations in reflecting their frequency-dependent dynamic characteristics. A method, the so-called transfer function model, which can reflect better the frequency-dependent complex stiffness and yet matches well with commercial programs, is suggested. The performance of the proposed technique in dynamic analysis is illustrated for two four-degree-of-freedom systems by comparing the results with those of the Voigt model. *Communicated by G. Hulbert.

2414 エンジンマウント系の振動 : 流体連成解析

2414 エンジンマウント系の振動 : 流体連成解析

Active rubber mounts by means of piezoelectric actuators,experimental work

This paper proposes an experimental mock-up which aims to validatea new concept of a piezo-rubber mount. This new concept is based upon thecombination of an electrically-monitored active piezoelectric block with apassive rubber mount. An adaptive control law is then used for an off-lineidentification and control of the force transmissibility. The new hybrid mountis shown to be very efficient and significantly improves the transfer betweendisturbances and receiving components.

Vehicle ride enhancement using simulation assisted rubber mount design

The work reported here describes the results of a series of parameter studies to investigate the relative effects of varying each suspension component parameter on vehicle ride comfort. The vehicle sprung mass was identified as having a significant effect on the overall ride index. A methodology is prescribed by which the ride performance of a vehicle with a passive suspension arrangement could be maintained at a predetermined limit irrespective of the vehicle load condition by suitable design of the suspension strut rubber mounts.

1307 A Study of Stiffness Characteristic of Hydraulically damped rubber mount

1307 A Study of Stiffness Characteristic of Hydraulically damped rubber mount

442 An Introduction of Research and Development of Passive Hydraulically Damped Rubber Mount of Automotive Powertrain

442 An Introduction of Research and Development of Passive Hydraulically Damped Rubber Mount of Automotive Powertrain

Numerical and experimental investigations on the isolation of structure-borne sound using rubber mounts

Rubber mounts are frequently used for the isolation of structure-borne vibrations in the low-frequency range. However, not much research has been done in the acoustic frequency range. In this essay the sound isolation behavior of rubber mounts is investigated by means of the finite element method. The static preload is described by a nonlinear elastic material model. For dealing with the dynamic behavior, a linear viscoelastic model with frequency-dependent parameters is used. The influence of different material parameters on the transmissibility and on the dynamic stiffness of different resilient elements is examined. The calculations are compared with experimental data. For this a measurement apparatus has been set up based on ISO 10 846. Further on, the interaction between resilient elements and a structure supported on them is investigated. The supported structure is chosen to be a plate made of steel. The plate is not regarded to be rigid. The influence of different mounts on the structure-borne sound of the plate is examined. Additionally, it is researched how the sound isolation changes when eigenfrequencies of the supported plate and of the elastic mounts are approximately the same.

Resilient mounting of engines

In any type of vehicle a number of mechanical sources generate structure-borne noise. The energy is transmitted from excitation points to surrounding structures. These radiate noise externally and internally. The most commonly used method to reduce the radiated noise is to mount the sources resiliently to the supporting foundation. The insertion loss due to the resilient mounting can in many cases be extremely poor. This could be due to the break down of the stiffness of the foundation in the audible frequency range. At the same time the stiffness of the mounts could be increased drastically as compared to the static stiffness. A test rig and measurement procedures for determining the dynamic properties of mounts are described. Measured and predicted results are compared for rubber mounts with simple geometries. The insertion loss of a resilient mounting very much depends on the location of the engine feet on a foundation. Case studies relating to passenger vessels and catamarans built with aluminum and sandwiched are presented. Reduction of both noise and weight is discussed.

Localizing Energy Sources and Sinks in Plates Using Power Flow Maps Computed From Laser Vibrometer Measurements

This paper presents an experimental method especially adapted for the computation of structural power flow using spatially dense vibration data measured with scanning laser Doppler vibrometers. In the proposed method, the operational deflection shapes measured over the surface of the structure are curve-fitted using a two-dimensional discrete Fourier series approximation that minimizes the effects of spatial leakage. From the wavenumber-frequency domain data thus obtained, the spatial derivatives that are necessary to determine the structural power flow are easily computed. Divergence plots are then obtained from the computed intensity fields. An example consisting of a rectangular aluminum plate supported by rubber mounts and excited by a point force is used to appraise the proposed method. The proposed method is compared with more traditional finite difference methods. The proposed method was the only to allow the localization of the energy source and sinks from the experimental divergence plots.

A Pressure Projection Method for Nearly Incompressible Rubber Hyperelasticity, Part II: Applications

In the first part of this paper a pressure projection method was presented for the nonlinear analysis of structures made of nearly incompressible hyperelastic materials. The main focus of the second part of the paper is to demonstrate the performance of the present method and to address some of the issues related to the analysis of engineering elastomers including the proper selection of strain energy density functions. The numerical procedures and the implementation to nonlinear finite element programs are presented. Mooney-Rivlin, Cubic, and Modified Cubic strain energy density functions are used in the numerical examples. Several classical finite elasticity problems as well as some practical engineering elastomer problems are analyzed. The need to account for the slight compressibility of rubber (finite bulk modulus) in the finite element formulation is demonstrated in the study of apparent Young’s modulus of bonded thin rubber units. The combined shear-bending deformation that commonly exists in rubber mounting systems is also analyzed and discussed.

PERFORMANCE ANALYSIS OF AN ENGINE MOUNT FEATURING ER FLUIDS AND PIEZOACTUATORS

Conventional rubber mounts and various types of passive or semi-active hydraulic engine mounts for a passenger vehicle have their own functional aims on the limited frequency band in the broad engine operating frequency range. In order to achieve high system performance over all frequency ranges of the engine operation, a new type of engine mount featuring electro-rheological(ER) fluids and piezoactuators is proposed in this study. A mathematical model of the proposed engine mount is derived using the bond graph method which is inherently adequate to model the interconnected hydromechanical system. In the low frequency domain, the ER fluid is activated upon imposing an electric field for vibration isolation while the piezoactuator is activated in the high frequency domain. A neuro-control algorithm is utilized to determine control electric field for the ER fluid, and H∞ control technique is adopted for the piezoactuator Comparative works between the proposed and single-actuating(ER fluid only or piezoactuator only) engine mounts are undertaken by evaluating force transmissibility over a wide operating frequency range.

Modeling and Control of an Engine Mount Using ER Fluids and Piezoactuators

This paper presents a new prototype of an engine mount for a passenger vehicle featuring ER(elector-rheological) fluids and piezoactuators. Conventional rubber mounts and various types of passive or semi-active hydraulic engine mounts have their own functional aims on the limited frequency band in the board engine operating frequency range. However, the proposed engine mount covers all frequency range of the engine operation. A mathematical model of the proposed engine mount is derived using the bond graph method which is inherently domain, the ER fluid is activated upon imposing electric field for vibration isolation while the piezoactuator. Computer control electric fluid for the ER fluid H.inf. cotrol technique is adopted for the piezoactuator. Computer simulation is undertaken in order to demonstrate isolation efficiency of the engine mount over wide operating frequency range.

Recent developments in the in‐situ measurement of sediment geoacoustic properties

The latest version of the in‐situ sediment acoustic measurement system (ISSAMS) allows direct, in‐situ measurement of sediment geoacoustic properties. Geoacoustic probes, which are mounted on a rigid frame, are inserted into the sediment hydraulically. The entire operation is controlled and monitored in real‐time from the surface. Data is collected and processed by a wet‐side computer and transmitted to the surface for waveform display and analysis. Video cameras both monitor insertion of probes and provide preliminary indication of sediment type. A seabird CTD is used to measure bottom water temperature, salinity, and sound speed. Sediment compressional wave velocity and attenuation are measured over pathlengths of 40 to 110 cm and at depths of between 0 to 50 cm below the sediment–water interface. Pulsed sine waves are transmitted at 58‐kHz and time delays and voltages are used to determine values of velocity and attenuation between identical radial‐poled ceramic cylinders (two transmit and two receive). Shear wave velocity and attenuation are measured using a similar pulse technique. Bimorph bender elements mounted in flexible silicone rubber mounts and driven at 100 to 2000 Hz to generate shear waves. Values of sediment geoacoustic properties from muddy sediments of Eckernförde Bay, Baltic Sea and carbonate sediments of the Florida Keys presented used to illustrate the operation and utility of the new system.

Using mechanical-acoustical reciprocity for diagnosis of structure borne sound in vehicles

The low frequency interior noise in cars is for a large part the result of structure borne excitation. The transfer of the structure borne sound involves a large number of components of the engine suspension, wheel suspension and chassis which are all potentially contributing to the overall noise level. This process can be analyzed through acombination of transfer function measurements with operational measurements under normal vehicle conditions. This technique, called transfer path analysis, requires large numbers of transfer function measurements with excitation of the body or cabin at the rubber mountings. Unfortunately, bad access to these crucial measurement locations causes either high instrumentation and measurement effort or less accurate measurement data. The practicality and quality of the measurements can be improved by using reciprocal measurements for the mechano-acoustic transfer of the body or cabin structure; a loudspeaker in the cavity is used for the reciprocal excitation. The reciprocity technique also allows better insight in the acoustic response of the cavity

Calculation of the stress-strain state of axisymmetrical rubber-metal products

The use of B-splines of arbitrary order with an arbitrary node pattern is discussed in application to the calculation of rubber elements in combination hinges. The proposed B-spline technology is applicable to the analysis of other problems as well. To achieve high accuracy, it requires considerably fewer parameters than when conventional basis functions in finite-element analysis. Computer results are given for rubber elements in the pressing of single-ring combination hinges and for thick-walled rubber mounts in axial compression.

Vibration isolation of superconducting magnets

In order to improve image resolution and magnetic field uniformity in a magnetic resonance imaging device, the vibrations and loads produced by the cryocooler are isolated from the superconducting magnet and cryostat. The vibrations and loads are isolated through the use of flexible, laminated copper connectors and rubber mounts.

Linear analysis of automotive hydro-mechanical mount with emphasis on decoupler characteristics

A hydro-mechanical mount for an automotive engine can provide superior stiffness and damping characteristics which may vary with frequency and excitation amplitude. In order to better understand such a passive device, a linear time-invariant model with lumped mechanical and fluid elements is proposed and validated by comparing dynamic stiffness spectra predictions with experimental data over the frequency range 1–50 Hz. Special emphasis has been placed on the modeling of both free and fixed type decouplers. Most, if not all, of the prior models have been shown to be the special cases of the proposed four-degree-of-freedom system model. Several reduced or simplified forms of this model have been examined, and parametric design studies have been carried out. The performance of a typical hydro-mechanical mount has also been compared with the conventional rubber mount for the resonance control and vibration isolation characteristics. Inappropriateness of the low frequency model beyond 100 Hz is identified. Other limitations associated with the linear models are identified and future research issues have been discussed briefly.

Finite deformation of compressible bonded rubber mounts

Bearings for bridges, earthquake isolation bearings for buildings, and elements in vehicle suspensions may be made from one or more layers of elastomer between rigid steel plates to which the elastomer is bonded. Using simplifying assumptions based on previous work, simple and explicit forms of solution are developed for finite (non-linear) deformation of bonded blocks, in plane or axisymmetric strain, with special reference to compressible elastic materials. The qualitative behaviour of the explicit form of solution is reasonable and on linearizing it agrees with published experimental and theoretical results for small deformation. The explicit form of solution also compares well with such experimental results as are available for finite deformation and with finite element calculations. Application of the results to laminated blocks, where compressibility is expected to be important is illustrated, and an assessment of the effect of the bulk compressibility of the rubber is offered.

Dynamic Analysis of Engine-Mount Systems

This paper examines the forced response of an airplane engine supported by an elastic foundation. It is assumed that the vibrations of the engine and the foundation are small enough such that the equations of motion are linear. The engine is modeled as a rigid body connected to the foundation by standard industrial rubber mounts which act as three-dimensional springs with a significant amount of hysteresis damping. Three fundamental models of the foundation are considered; rigid, statically flexible, and dynamically flexible. In the flexible cases, the foundation is modeled as a clamped circular plate, infinite plate, or any structure identified by a finite element stiffness matrix. In all cases, the mass, stiffness, and damping matrices of the engine-mount system are constructed and the frequency response to the rotating unbalance is determined. For the infinite and clamped circular plate cases, analytical methods are used to determine the real and imaginary parts of the flexibility matrix at different frequencies in response to the harmonic forces transmitted to the plate through the rubber mounts. It is shown here that the foundation elasticity may have a significant effect on the engine vibration and the mounting forces transmitted from the engine to the structure. It is also shown that only the dynamic model of the foundation is able to capture the correct response of the system at frequencies close to the foundation’s natural frequencies.

A Study on Semi-active Control for engine Mounts by Real-Time Simulation.

Hydraulic engine mounts are replacing conventional rubber mounts in order to provide better ride quality and to reduce noise. In this paper, a real-time semi-active control method of hydraulic mount damping is presented. Although it is desirable to use the state of fluid motion as the feedback signal, it is difficult to measure this mortion directly. As an alternative, a simulator which estimates fluid motion from the measurable vehicle vibration is developed. However, real-time control is limited by the speed of computation; thus it is of interest to find optimal numerical integration algorithms. Of the Euler, Adams-Bashforth, Runge-Kutta and central difference methods, the latter method is the most feasible for this application because steady-state error becomes negligible even with large sampling periods. It is demonstrated experimentally that this simulator is effective for vibration control.