On the Ordinary, Generalized, and Pseudo-Variational Equations of Motion in Nonlinear Elasticity, Piezoelectricity, and Classical Plate Theories

1995 ◽  
Vol 62 (2) ◽  
pp. 471-478 ◽  
Author(s):  
Yi-Yuan Yu
Keyword(s):  
Nonlinear Elasticity ◽  
Variational Equation ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Laminated Composite ◽  
Classical Type ◽  
Order Effects ◽  
Variational Equations ◽  
Plate Equations ◽  
Higher Order Effects

Ordinary, generalized, and pseudo-variational equations of motion in three-dimensional theories of nonlinear elasticity and piezoelectricity are presented systematically. These are applied to the derivations of plate equations of the classical type. In contrast to the derivations of plate equations that include thickness and higher-order effects, it is shown that the volume and surface integrals in a three-dimensional ordinary variational equation of motion must now be used jointly in a coupled manner. Details are demonstrated by first treating a classical linear plate. Equations of the classical type for large deflections of laminated composite and piezoelectric plates are then derived, with the famous von Ka´rma´n equations of an isotropic homogeneous plate deducible as a special case. Interrelationship among various plate equations is emphasized.

Axisymmetric acoustic scattering by vortices

2002 ◽  
Vol 473 ◽  
pp. 275-294 ◽  
Author(s):  
Y. HATTORI ◽  
STEFAN G. LLEWELLYN SMITH
Keyword(s):  
Mach Number ◽  
Born Approximation ◽  
Acoustic Waves ◽  
Three Dimensional ◽  
Acoustic Scattering ◽  
Order Effects ◽  
Incoming Wave ◽  
Spherical Vortex ◽  
The Difference ◽  
Higher Order Effects

The scattering of acoustic waves by compact three-dimensional axisymmetric vortices is studied using direct numerical simulation in the case where the incoming wave is aligned with the symmetry axis and the direction of propagation of the vortices. The cases of scattering by Hill’s spherical vortex and Gaussian vortex rings are examined, and results are compared with predictions obtained by matched asymptotic expansions and the Born approximation. Good agreement is obtained for long waves, with the Born approximation usually giving better predictions, especially as the difference in scale between vortex and incoming waves decreases and as the Mach number of the flow increases. An improved version of the Born approximation which takes into account higher-order effects in Mach number gives the best agreement.

Frequencies and Loss Factors of Multicored Sandwich Beams

1978 ◽  
Vol 100 (4) ◽  
pp. 667-674 ◽  
Author(s):  
D. K. Rao
Keyword(s):  
Equations Of Motion ◽  
Sandwich Beam ◽  
Wide Frequency Range ◽  
Order Effects ◽  
Maximum Loss ◽  
The Core ◽  
The Face ◽  
Method Analysis ◽  
Higher Order Effects ◽  
Loss Factors

The sandwich beam analyzed in the present paper consists of layers of elastic and viscoelastic material of arbitrary thickness and material. No restrictive assumptions are made on the bending and shear rigidities of the cores. Higher-order effects like rotatory inertia, bending, and extension of the core, which were ignored in previous theories, are included in the equations of motion presented herein. Exact equations for finding resonant frequencies and loss factors are given for simply-supported beams, while for other boundary conditions, these quantities are computed by variational method. Analysis of numerical results indicates that unsymmetricizing the face layers is superior to unsymmetricizing the core layers. It also showed that uniformly high damping over a wide frequency range can be obtained only by the use of stiff cores, but this is followed by a reduction in the maximum loss factor.

On the general homogenization of von Kármán plate equations from three-dimensional nonlinear elasticity

2016 ◽  
Vol 15 (01) ◽  
pp. 1-49 ◽  
Author(s):  
Igor Velčić
Keyword(s):  
Nonlinear Elasticity ◽  
Three Dimensional ◽  
Von Karman ◽  
Elasticity Equations ◽  
Plate Equations ◽  
Von Kármán Plate ◽  
Von Kármán ◽  
Three Dimensional Elasticity

Starting from three-dimensional elasticity equations we derive the model of the homogenized von Kármán plate by means of [Formula: see text]-convergence. This generalizes the recent results, where the material oscillations were assumed to be periodic.

A Finite Element Formulation for the Dynamic Analysis of Machine Components Fabricated From Composite Materials

1992 ◽  
Author(s):  
A. Semos ◽  
C. Chassapis
Keyword(s):  
Finite Element ◽  
Composite Materials ◽  
Dimensional Space ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Laminated Composite ◽  
Element Formulation ◽  
Reinforced Composite ◽  
External Forces ◽  
Three Dimensional Space

Abstract In this paper finite element procedures are presented for analyzing the elastic-dynamic behavior of mechanical components fabricated from fiber-reinforced composite materials. An arbitrarily laminated composite plate element is created which allows the analysis of components that are moving in three dimensional space. The five D.O.F. per node static model of S. C. Panda and R. Natarajan is used as a basis for the derivation of the dynamic model. The elemental equations of motion are derived from Hamilton’s Principle. The formulation considers the total kinetic and strain energies of the moving element, together with the work due to bending, caused by the transversely acting external forces, as well as that due to the foreshortening of the element, caused by axially applied loads.

On the motion of comet P/d’Arrest

1974 ◽  
Vol 22 ◽  
pp. 145-148
Author(s):  
W. J. Klepczynski
Keyword(s):  
Equations Of Motion ◽  
Variational Equations ◽  
Partial Derivatives

AbstractThe differences between numerically approximated partial derivatives and partial derivatives obtained by integrating the variational equations are computed for Comet P/d’Arrest. The effect of errors in the IAU adopted system of masses, normally used in the integration of the equations of motion of comets of this type, is investigated. It is concluded that the resulting effects are negligible when compared with the observed discrepancies in the motion of this comet.

Validation of a Belt Model for Prediction of Hub Forces from a Rolling Tire4

2009 ◽  
Vol 37 (2) ◽  
pp. 62-102 ◽  
Author(s):  
C. Lecomte ◽  
W. R. Graham ◽  
D. J. O’Boy
Keyword(s):  
Internal Pressure ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Prediction Method ◽  
Analytical Models ◽  
Beam Model ◽  
Impedance Boundary ◽  
Bending Waves ◽  
Tire Rotation ◽  
Three Dimensional Models

Abstract An integrated model is under development which will be able to predict the interior noise due to the vibrations of a rolling tire structurally transmitted to the hub of a vehicle. Here, the tire belt model used as part of this prediction method is first briefly presented and discussed, and it is then compared to other models available in the literature. This component will be linked to the tread blocks through normal and tangential forces and to the sidewalls through impedance boundary conditions. The tire belt is modeled as an orthotropic cylindrical ring of negligible thickness with rotational effects, internal pressure, and prestresses included. The associated equations of motion are derived by a variational approach and are investigated for both unforced and forced motions. The model supports extensional and bending waves, which are believed to be the important features to correctly predict the hub forces in the midfrequency (50–500 Hz) range of interest. The predicted waves and forced responses of a benchmark structure are compared to the predictions of several alternative analytical models: two three dimensional models that can support multiple isotropic layers, one of these models include curvature and the other one is flat; a one-dimensional beam model which does not consider axial variations; and several shell models. Finally, the effects of internal pressure, prestress, curvature, and tire rotation on free waves are discussed.

Time after time: support for memory accounts of temporal preparation.

2019 ◽  
Author(s):  
Joe Butler ◽  
Samuel Ngabo ◽  
Marcus Missal
Keyword(s):  
Response Times ◽  
Reaction Times ◽  
Evidence Base ◽  
Higher Order ◽  
Order Effects ◽  
Previous Trial ◽  
Adaptive Responses ◽  
Temporal Preparation ◽  
Subsequent Trial ◽  
Higher Order Effects

Complex biological systems build up temporal expectations to facilitate adaptive responses to environmental events, in order to minimise costs associated with incorrect responses, and maximise the benefits of correct responses. In the lab, this is clearly demonstrated in tasks which show faster response times when the period between warning (S1) and target stimulus (S2) on the previous trial was short and slower when the previous trial foreperiod was long. The mechanisms driving such higher order effects in temporal preparation paradigms are still under debate, with key theories proposing that either i) the foreperiod leads to automatic modulation of the arousal system which influences responses on the subsequent trial, or ii) that exposure to a foreperiod results in the creation of a memory trace which is used to guide responses on the subsequent trial. Here we provide data which extends the evidence base for the memory accounts, by showing that previous foreperiod exposures are cumulative with reaction times shortening after repeated exposures; whilst also demonstrate that the higher order effects associated with a foreperiod remain active for several trials.

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