Viscoelastic Spring Research Articles

Mouvements propres d'un système à 1 D.D.L. avec amortissement viscoélastique

In this note, one considers a 1- d.o.f. oscillator consisting of a mass and a viscoelastic spring, the rheology of which is represented by a generalized so-called Biot's model with 2 n + 1 parameters. It is proved that its n + 2 independent eigenmotions are of the following nature: two eigenmotions damped with or without oscillations (as in the case of classical viscous damping) and n eigenmotions damped without oscillations which are induced by the viscoelastic rheology. To cite this article: P. Muller, C. R. Mecanique 333 (2005).

A Study on Construction of Tire Model with Viscoelasticity

This paper focuses on the tire force characteristics related to the vehicle speed. We constructed a mechanical tire model using a Voigt-Type viscoelastic spring system for the tread rubber. And, we analyze the force distribution along the contact length, the dependence of vehicle speed to the tire forces and the moments to a change in sideslip angle. Finally, it is shown that the tire model has good agreement with actual measurements results qualitatively, and also it is found that the characteristics of lateral force have independence to the vehicle speed.

Are the eigensolutions of a 1-d.o.f. system with viscoelastic damping oscillatory or not?

In this note, one considers a 1 d.-o.-f. oscillator consisting of a mass and a viscoelastic spring, the rheology of which is represented by a so-called Zener 3-parameters model. Such a system has three eigenmotions: two of them are damped with or without oscillations (as in the case of viscous damping), the third is damped without oscillation. Introducing appropriate parameters, one has performed a detailed discussion of the nature of these eigenmotions.

Frequency-Dependent Viscoelastic Structural Elements for Passive Broad-Band Vibration Control

The effective control of vibration is essential in many systems, including remote sensing applications where high resolution is needed to observe features on Earth from a space platforn. It is advantageous to have a passive system that has the ability to effectively reduce the response of a structure due to base excitation over a large frequency range that may be changing. In this manner, not only is the system self-contained and reliable, but also it does not use limited resoirces available in a space environment that an active system requires. A vibration amplitude limiting system has been developed that uses both vibration isolation and absorber components. With the appropriate stiffness and damping parameters chosen, the device can limit oscillation amplitudes to an acceptable level over a broad prescribed frequency range. By using viscoelastic structural elements, both spring and damping properties are introduced in a single element, which also demonstate favorable frequency-dependent response. A translation amplitude limiting vibration system has been designed, analyzed, built, and tested. Both the theoretical and the experimental transmissibility as a function of frequency are determind. A summary of these results will be presented along with a comparison to a more conventional vibration isolation/absorber system using non-frequency-dependent elements.

Analysis of a viscoelastic spring–mass model

In this paper we consider a linear wave equation with strong damping and dynamical boundary conditions as an alternative model for the classical spring–mass–damper ODE. Our purpose is to compare analytically these two approaches to the same physical system. We take a functional analysis point of view based on semigroup theory, spectral perturbation analysis and dominant eigenvalues.

Tooth-implant connection: some biomechanical aspects based on finite element analyses.

This study investigated, with the use of two- and three-dimensional finite element analysis, the peri-implant stress that occurred during loading of a tooth that was rigidly connected to a distally placed implant. A fixed bond between the bone and the implant was assumed, while the periodontal ligament was represented by means of three-dimensional nonlinear visco-elastic spring elements. Two different loading conditions were compared in the study: i) an axially directed static load of 50 kg that was applied to the tooth for 10 s, and ii) a transitional load of 50 kg that was applied for 5 milliseconds. Load duration appeared to have a greater influence than load intensity on the stress distribution in the bone around an implant and a rigidly connected tooth. Static load is, therefore, potentially more harmful for peri-implant bone than transitional load. The periodontal ligament seems to play a key role in the stress distribution between a tooth and a rigidly connected implant.

New concepts in diastolic dysfunction and diastolic heart failure: Part II: causal mechanisms and treatment.

As described in Part I of this 2-part article,1 diastolic heart failure is common and causes significant alterations in prognosis. In Part II, experimental studies that have provided insight into the mechanisms that cause diastolic heart failure will be described.2–19⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓ In addition, current treatment strategies and the design of future clinical trials of diastolic heart failure will be discussed. The development of truly effective therapy for diastolic heart failure depends on gaining a clear understanding of the basic mechanisms that alter diastolic function and the ability to efficiently target these mechanisms to correct these abnormalities in diastolic function. Conceptually, the mechanisms that cause abnormalities in diastolic function that lead to the development of diastolic heart failure can be divided into factors intrinsic to the myocardium itself (myocardial) and factors that are extrinsic to the myocardium (extramyocardial; Table 1). Myocardial factors can be divided into structures and processes within the cardiac muscle cell (cardiomyocyte), within the extracellular matrix (ECM) that surrounds the cardiac muscle cell, and that activate the autocrine or paracrine production of neurohormones. Each of these mechanisms are active in the major pathological processes that result in diastolic dysfunction and heart failure. Myocardial and extramyocardial mechanisms, cellular and extracellular mechanisms, and neurohumoral activation each play a role in the development of diastolic heart failure caused by ischemia, pressure-overload hypertrophy, and restrictive and hypertrophic cardiomyopathy. View this table: Table 1105290. Diastolic Heart Failure: Mechanisms ### Cardiomyocyte Diastolic dysfunction can be caused by mechanisms that are intrinsic to the cardiac muscle cells themselves. These include changes in calcium homeostasis caused by (1) abnormalities in the sarcolemmal channels responsible for short- and long-term extrusion of calcium from the cytosol, such as the sodium calcium exchanger and the calcium pump; (2) …

テンション構造用付加減衰機構を有するスタジアム屋根の振動性状

The authors have proposed a damping system composed of visco-elastic material and spring, which is invented as a device for hybrid tension structures with small damping. In this paper, the proposed system is applied to front stays for suppressing vibration of the cantilevered football staduim roof tensioned with counteracting back stays. Vibration tests were carried out and compared with the theoretical values, proving the effectiveness of the system.

On-line chatter detection and control in boring based on an electrorheological fluid

For on-line chatter avoidance in boring, this paper presents an adaptive control system which, based on a novel design of the boring bar containing an Electrorheological (ER) fluid, automatically adjusts the dynamics of the bar according to the information from the monitored sensor signal. For detecting chatter rapidly and accurately, artificial neural networks are used to decontaminate the sensor signal and recognize the chatter omen. Once chatter is detected, a strength regulation strategy of the electric field applied to the ER fluid in the bar is used to suppress chatter. When a certain electric field is applied to the ER fluid in the bar it behaves as a viscoelastic spring with nonlinear vibration characteristics. Based on the nonlinear vibration characteristics of the ER fluid, the strength regulation strategy is to tune the electric field strength so that the dynamics of the bar is sensitive to the minute change of the vibration amplitude. Experiments show that chatter in boring can be avoided by using this control system.

A physiological articulatory model for simulating speech production process.

A physiological articulatory model has been developed to simulate the dynamic actions of speech organs during speech production. This model represents the midsagittal region of the tongue, jaw, hyoid bone, and the vocal tract wall in three dimensions. The soft tissue of the tongue is outlined in the midsagittal and parasagittal planes of MR images obtained from a male Japanese speaker, and constructed as a 2-cm thick layer. The palatal and pharyngeal walls are constructed as a hard shell of a 3-cm left-to-right width. The jaw and hyoid bone are modelled to yield rotation and translation motions. The muscle structure in the model is identified based on volumetric MR images of the same speaker. A fast simulation method is developed by modeling both the soft tissue and rigid organs using mass-points with two types of links: viscoelastic springs with a proper stiffness for connective tissue, and extremely high stiffness for bony organs. Muscle activation signals are generated by a model control strategy based on the target-reaching task, and then fed to drive the model to approach the targets. The model demonstrated realistic behaviors similar to coarticulation in human speech production (Dang and Honda, 1998, 1999, 2000).

STEADY-STATE VIBRATIONS OF AN ELASTIC RING UNDER A MOVING LOAD

The steady state response of an elastic ring subjected to a uniformly moving load is considered. It is assumed that the ring is attached by visco-elastic springs to an immovable axis and the load is radial and point-like. An exact analytical solution of the problem is obtained by applying the “method of images”. The ring patterns are analyzed. It is shown that for small velocities of the load the ring pattern is almost perfectly symmetric with respect to the loading point. If the load velocity is smaller, but comparable with the minimum-phase velocityVminph of waves in the ring, the pattern becomes slightly asymmetric due to viscosity of the springs. When the load moves faster than Vminphthe pattern becomes wave-like and substantially asymmetric. The condition of resonance is found. It is shown that resonance occurs when either the ring length is divisible to the wavelength of a wave radiated by the load or the velocity of the load is close toVminph .

The stability of the equilibrium of a wing in an unsteady flow

The stability of the equilibrium position of a wing is investigated. The wing is modelled by a heavy rigid body with a fixed point and is close in shape to a thin plate. The wing is fastened using a viscoelastic material which can be modelled by non-linear viscoelastic springs that keep the wing in a position close to horizontal. The motion of the wing is described by a system of non-linear ordinary integrodifferential equations which, using the model adopted, take account of the unsteady nature of the flow past the wing and the viscoelastic properties of the spring material. The stability of the equilibrium under persistent disturbances is analysed. This analysis is based on the use of series similar to those in the first Lyapunov method. The stability of the equilibrium for purely rotational motions of the wing about the longitudinal axis is investigated in the critical case of a single zero root of the characteristics equation. The Lyapunov constants which solve the stability problem are indicated.

A design of laryngeal structures for a physiological articulatory model

A model of the hyoid–larynx complex is designed and incorporated into a physiological articulatory model. The previously reported articulatory model [Dang and Honda, Proc. ICSLP98] consists of the tongue, mandible, hyoid bone, and vocal tract wall. The aim of this work is to include the laryngeal structures to simulate the tongue–larynx interaction which is observed in natural speech. The framework of laryngeal structures is composed of the thyroid, cricoid, and arytenoid cartilages, which are connected by muscles, ligaments, and joints. The form and geometry of the cartilages are extracted from volumetric MR images of a male speaker and represented in a quasi-3D shape. They are modeled to yield joint rotation and translation as well as vertical movements. The ligaments and muscles are represented by mass points with viscoelastic springs, and the cartilages are composed by springs with an extremely large stiffness. Laryngeal factors of F0 control such as cricothyroid rotation and laryngeal vertical movement are demonstrated in the simulation, and plausible dynamic behaviors of the tongue–larynx interaction are observed. The performance of the model is tested by comparison of acoustic output from the model with recorded speech.

STABILITY OF A JOINTED FREE–FREE BEAM UNDER END ROCKET THRUST

This paper deals with the stability of a flexible space structure subjected to an end rocket thrust. The thrust acts upon the structure as a follower non-conservative force, thus the structure can lose its stability by flutter or divergence depending on the system parameters. It is assumed that the articulated free–free beams are subjected to a tangential follower force. The model consists of two viscoelastic beams interconnected by two kinds of joints. One of the joints is composed of a rotational viscoelastic spring while another is a shear viscoelastic spring. A FEM formulation of the articulated structure is performed. Bending flutter or post-flutter divergence are shown to occur depending on the joint rigidity and the internal damping.

Two-Dimensional Contact Pressure Distribution of a Radial Tire in Motion

Abstract The two-dimensional contact pressure distribution of a running radial tire under load is a fundamental property of the tire structure. The two-dimensional contact pressure distribution in the static case and the one-dimensional contact pressure distribution in the dynamic case were previously analyzed for a spring bedded ring model consisting of a composite belt ring and a spring system for the sidewall and the tread rubber. In this paper, a Voigt-type viscoelastic spring system is assumed for the sidewall and the tread rubber. We analyzed the dynamic deformation of the belt ring in a steady state, and obtained the two-dimensional dynamic contact pressure distribution at speeds up to approximately 60 km/h. The predicted contact pressure distribution for a model with appropriate values for the damping coefficient of each constituent rubber is shown to be in good agreement with experimental results. It is a characteristic feature that increasing velocity yields an increase in the pressure at the leading edge of the crown centerline in the contact area and at the trailing edge of the shoulder line.

Use of a Viscoelastic Model for the Seismic Response of Base-Isolated Buildings

Due to recent developments in elastomer technology, seismic isolation using elastomer bearings is rapidly becoming an acceptable design tool to enhance structural seismic margins and to protect people and equipment from earthquake damage. With proper design of isolators, high-energy seismic input motions can be transformed into low-frequency, low-energy harmonic motions, and the accelerations acting on the isolated building may be significantly reduced. Several alternatives exist for the modeling of the isolators. This study is concerned with the use of a viscoelastic model to predict the seismic response of base-isolated buildings. The in-house finite element computer code, SISEC has been modified to incorporate a viscoelastic spring element, and several simulations are performed. Then, the computed results have been compared with the corresponding observed data recorded at the test facility.

One-Dimensional Contact Pressure Distribution of Radial Tires in Motion

Abstract The contact pressure distribution and the rolling resistance of a running radial tire under load are fundamental properties of the tire construction, important to the steering performance of automobiles, as is well known. Many theoretical and experimental studies have been previously published on these tire properties. However, the relationships between tire performances in service and tire structural properties have not been clarified sufficiently due to analytical and experimental difficulties. In this paper, establishing a spring support ring model made of a composite belt ring and a Voigt type viscoelastic spring system of the sidewall and the tread rubber, we analyze the one-dimensional contact pressure distribution of a running tire at speeds of up to 60 km/h. The predicted distribution of the contact pressure under appropriate values of damping coefficients of rubber is shown to be in good agreement with experimental results. It is confirmed by this study that increasing velocity causes the pressure to rise at the leading edge of the contact patch, accompanied by the lowered pressure at the trailing edge, and further a slight movement of the contact area in the forward direction.

Method for Design of Dynamic Vibration Absorbers with Viscoelastic Springs.

This paper deals with a new and simple method of optimum design of dynamic vibration absorbers which consist of viscoelastic springs and auxiliary masses. If the usual method of design of dynamic absorbers is applied to an absorber with a viscoelastic spring, the stiffness and the loss factor of the spring are determined as optimum values corresponding to the given ratio of the auxiliary mass to the principal mass. The actual value of the loss factor, however, cannot be chosen arbitrarily, because it depends on the material of the visco-elastic spring. In the proposed method, the optimum condition can be found for any combination of values of the mass ratio and the loss factor of the viscoelastic spring. Therefore, dynamic absorbers can be realized for springs of arbitrary viscoelastic materials.

The motion of a carriage with constant velocity along a beam of infinite length resting on a base with two elastic characteristics

The vertical oscillations of an infinite Bernoulli-Euler beam resting on a viscous inertial base with two elastic characteristics under the action of a deforming carriage which is continuously moving at a constant velocity is considered. The carriage, consisting of a system of rigid bodies with viscoelastic couplings between them, makes contact with the beam via viscoelastic springs at a finite number of points which allows the small vertical oscillations of the elements of the carriage to be described by a system of ordinary differential equations with constant coefficients. A technique is proposed for obtaining the asymptotic forms of the solution at long times. The asymptotic forms of the solutions are presented and they are analysed for certain types of loads.

Online Measuring of the Edge Jaggedness of Wooden Materials During Machining

In sawing and milling laminated particle board a jaggedness on the edges arises in the form of notches and bulges which increase with increasing tool wear. This determines the workpiece quality and the tool life. Using a new gage, based on a viscoelastic damped plate spring, the edge jaggedness can be objectively measured at machining. Using a microcomputer a characteristic dimension is calculated from the measured edge profile. Investigations carried out with the jaggedness gage show the input variables of the edge jaggedness. Thus, for example, the influence of the feed per tooth, working engagement of the cutting edge and cutting speed in milling could be determined. The differences in the edge jaggedness between sawing and milling got clear. It could be shown that milling with a large angle of the axis would lead to a considerable reduction in edge jaggedness. Presently a process control for milling laminated particle board is being developed. Therein, the feed per tooth and the cutting speed in dependence on edge jaggedness should be so arranged that the tool wear by sufficient edge jaggedness is as small as possible.