Showing papers on "Thermoelastic damping published in 1970"
TL;DR: Composite materials macroscopic thermoelastic properties relationships to constituents properties, discussing effective thermal expansion coefficients and specific heats are discussed in this paper, where the authors also discuss the effect of specific heats.
592 citations
TL;DR: In this article, the authors discussed the nature of damping mechanisms and how the damping depends on the amplitude and frequency of the cyclic motion of the system. But they did not consider the effect of the frequency and amplitude on damping.
384 citations
TL;DR: The results of theoretical estimates for several thermal and thermoelastic constants of macroscopically isotropic composite materials are given in this paper, including elastic constants, thermal expansion coefficients, heat capacities (at constant volume and constant pressure), thermal conductivity, and related constants.
Abstract: The results of theoretical estimates are given for several thermal and thermoelastic constants of macroscopically isotropic composite materials. The composites considered consist of random mixtures of N isotropic constituents, at least ( N — 1) of which are presumed to be distributed in a particulate fashion, with the particles roughly spherical in shape. The results are based on "self-consistent" calcula tions, details of which are given in appendices.Equations (some of which are old, but are repeated for con venience) are given for the following quantities: elastic constants, thermal expansion coefficients, heat capacities (at constant volume and constant pressure), thermal conductivity, and, finally, Gruneisen and related constants.
253 citations
TL;DR: In this paper, the general theory of thermoelasticity of stressed solids is applied to the interpretation of experiments, which measure nonlinear thermo-elastic properties of solids, and illustrate this application by working out some examples.
Abstract: Publisher Summary This chapter presents the general theory of thermoelasticity of stressed solids to apply the theory to the interpretation of experiments, which measure nonlinear thermoelastic properties of solids, and to illustrate this application by working out some examples. Experimental work has been motivated by the development in recent years of the measurement of ultrasonic wave velocities as functions of stresses applied to the sample, and the measurement of the amplitude of the first harmonic generated by the passage of an ultrasonic fundamental wave through the sample. These experiments, and others such as the generation of sum- and difference-frequency waves by the interaction of two ultrasonic waves, are all interpreted from the same theoretical basis, namely nonlinear thermoelasticity of anisotropic solids. As thermoelasticity is characterized by a rather cumbersome notation, and indeed throughout the years by many different sets of such notation, corresponding to different theoretical and experimental situations, it is worthwhile to set out the general theory in a unified notation, suitable for application to all experiments on nonlinear thermoelasticity.
216 citations
126 citations
81 citations
TL;DR: In this article, it was shown that the unconstrained layer technique can be equal in damping effectiveness to the four-layer beam construction with the same total thickness of damping layers only when the modulus of elasticity of the non-constraint layer is of the same order of magnitude as for metals.
66 citations
TL;DR: In this paper, the stability of a cantilevered column subjected to a constant follower load in the presence of external damping is investigated, and it is shown that the critical load increases with increasing damping from the value of 20.05 EI/L 2 at zero damping to the limiting value of 37.7 EI /L 2 for large damping.
47 citations
TL;DR: In this article, a special kinematical viewpoint is taken, so that the elastic and plastic deformation processes can be considered separately, and this separation is also accommodated by a simplified thermodynamic theory of the deformation process.
40 citations
31 citations
TL;DR: In this paper, a model for the one-dimensional thermoelastic response of homogeneous isotropic metals to pulsed relativistic electron beam absorption was presented for polycrystalline aluminum, copper, and tantalum.
Abstract: A model is presented for the one‐dimensional thermoelastic response of homogeneous isotropic metals to pulsed relativistic electron beam absorption. The effect of the time dependence of the electron power pulse was examined for two cases: a delta function and a rectangular pulse of duration τ0. Equations were obtained in both cases which explicitly relate properties of the electron beam (energy absorption profile, total energy, and pulse duration) to properties of the material (density, dilatational wave velocity, and Gruneisen parameter). Experiments were performed to test the developed model for polycrystalline aluminum, copper, and tantalum. Electron beam dosimetry was accomplished by means of calorimetry and a passive film technique. Material response data was obtained by measuring the back surface motion by means of a laser interferometer. The experimental results indicated that an assumption of instantaneous energy deposition was incorrect except possibly for the case of the lowest Z metal, i.e., al...
TL;DR: In this article, it was shown that the relative energy contribution to the elastic stress of rubber-like materials appears to depend on the extension ratio at which thermoelastic measurements were carried out, in contradiction to the free energy additivity principle of the statistical theory of rubber elasticity.
Abstract: It has recently been noted by a number of workers that the relative energy contribution, fe/f, to the elastic stress of rubberlike materials appears to depend on the extension ratio at which thermoelastic measurements were carried out. This apparent strain dependence is in contradiction to the free energy additivity principle of the statistical theory of rubber elasticity. In this paper we resolve this problem by determining fe/f from the temperature coefficient of shear moduli. The shear moduli were not directly determined from measurements of shear, but calculated from tensile elongation data. This method circumvents the difficulty encountered in directly obtaining the relative energy contribution from stress—temperature data. Both constant length and constant stress thermoelastic measurements were used to obtain fe/f. A series of natural rubber samples, crosslinked in the presence of various amounts of n-hexadecane, were investigated. It is found that the relative energy contribution to the el...
TL;DR: In this article, the exact energy function for simple boundary conditions can be expressed in terms of only average values of the state variables and effective composite properties, and it is shown that the energy function can be derived from the average value of state variables.
TL;DR: In this article, a homogeneous continuum model is presented to describe the dynamic behavior of a laminated medium, including the effects of temperature variations, on the basis of assumed two-term expansions of the displacements and the temperature increments across the thicknesses of the layers, the state of deformation and temperature distribution in the composite are described by six fields, i.e., gross displacements, local deformations, gross temperatures and local temperature variations.
Abstract: A homogeneous continuum model is presented to describe the dynamic behavior of a laminated medium, including the effects of temperature variations. On the basis of assumed two-term expansions of the displacements and the temperature increments across the thicknesses of the layers, the state of deformation and the temperature distribution in the composite are described by six fields, i. e., gross displacements, local deformations, gross temperatures and local temperature variations. Balance equations are derived for the stress resultants and the first moments of the stresses across the thicknesses of the layers, as well as for resultant heat fluxes and their moments. A set of constitutive equations is presented for a laminated medium composed of layers of two anisotropic thermoviscoelastic solids. The special cases of isotropic thermoviscoelastic layers, anisotropic thermoelastic layers, and isotropic thermoelastic layers are discussed briefly.
TL;DR: In this paper, a simply supported rectangular thin elastic plate with a circular hole and subjected to heat flow is solved by the method of point matching, where the heat flow consists of an arbitrary temperature variation across the thickness of the plate but with no variation over the plate surfaces.
TL;DR: In this article, the authors investigated dielectric breakdown and mechanical damage in silicate glasses under high-intensity laser radiation in detail, from thermoelastic considerations a criterion for the validity of pos...
Abstract: Dielectric breakdown and mechanical damage in silicate glasses under high-intensity laser radiation are investigated in detail. From thermoelastic considerations a criterion for the validity of pos...
TL;DR: In this paper, the axisymmetric linear quasi-static thermoelastic equations for composite orthotropic cylindrical shells are solved in closed form for fixed-end boundary conditions.
TL;DR: In this article, the minimum-weight design of an elastic sandwich beam subject to the constraint that given loads and temperature changes produce a prescribed deflection at a specified cross-section is studied.
TL;DR: In this paper, a generalized theory of the thermoelasticity of an elastic half-space subjected to thermal and mechanical disturbances at its free surface is considered and an approximation of the general solution is obtained in closed form valid at temperatures near absolute zero, resulting in expresssions for temperature and strain response due to arbitrary inputs at the free boundary.
Abstract: The one-dimensional problem of an elastic half-space subjected to thermal and mechanical disturbances at its free surface is considered, using a generalized theory of the thermoelasticity which takes into account a finite velocity of propagation of thermal disturbances. An approximation of the general solution is obtained in closed form valid at temperatures near absolute zero, resulting in expresssions for temperature and strain response due to arbitrary inputs at the free boundary. These general expressions are applied to the particular problem of a step-strain input at the boundary and the results compared with previous work. The problem of a half-sine temperature pulse input is also treated.
19 May 1970
TL;DR: In this paper, a uniqueness theorem for the solution of the initial mixed boundary-value problem characterized by the equations of the above mentioned theory for thermo-elastic shells is presented.
Abstract: A recent paper by the authors contains an approximate linear theory for thermoelastic shells (and plates) which is derived from the three-dimensional equations. Under isothermal conditions, the equations of this theory are of an elastic Cosserat surface. The present paper is mainly concerned with a uniqueness theorem for the solution of the initial mixed boundary-value problem characterized by the equations of the above mentioned theory for thermo-elastic shells. (Author)
TL;DR: In this article, a technique for obtaining directly the energy absorption profile of a solid heated by pulses of intense radiation was described, and the appropriate thermoelastic equations were solved for two cases of particular interest, instantaneous deposition and energy absorbed at a constant rate.
Abstract: A technique is described of obtaining directly the energy absorption profile of a solid heated by pulses of intense radiation. The appropriate thermoelastic equations were solved for two cases of particular interest, instantaneous deposition and energy absorbed at a constant rate. The dynamic response of aluminum and copper to electrons of everage energy 1.5 MeV was measured by means of a laser interferometer, and the resulting energy profiles were compared with profiles obtained using a thin film dosimetry technique. The resulting quantitative agreement with the thermoelastic theory is discussed.
TL;DR: In this article, a new technique for direct measurement of the Gruneisen parameter of elastic materials is presented, which employs the measurement of one-dimensional thermoelastic response of materials exposed to a pulsed electron beam.
Abstract: A new technique for the direct measurement of the Gruneisen parameter of elastic materials is presented. The technique employs the measurement of the one‐dimensional thermoelastic response of materials exposed to a pulsed electron beam. The measured values of the Gruneisen parameter for single crystals of both metals and semiconductors are in excellent agreement with thermal values.
TL;DR: In this paper, the non-axisymmetric thermal stress distribution in an infinite elastic solid containing an external stress-free crack with prescribed heat flux is investigated, and the problem is formulated in terms of a complete set of harmonic functions and leads to a set of mixed, coupled boundary value problems.
TL;DR: In this paper, a general formulation of local stability analysis of thermoelastic continuous systems subjected to non-conservative forces is established, and the numerical solutions of the flutter load in the column problem are presented.
TL;DR: In this paper, the relationship between the displacements of the inside and outside surfaces of the cylinder and the radial stresses and the mechanical and thermophysical properties of the components, the reinforcement ratio, and the ratio of the radii is investigated.
Abstract: The temperature stresses and displacements are determined in an elastic circular cylinder of reinforced multilayer material. The relationship between the displacements of the inside and outside surfaces of the cylinder and the radial stresses and the mechanical and thermophysical properties of the components, the reinforcement ratio, and the ratio of the radii is investigated. The results are used to interpret the behavior of wound glass-reinforced plastic products under varying temperature conditions and during the curing stage.
TL;DR: In this paper, the frequency dependence of dislocation damping in niobium was measured in the megahertz frequency range at 293 and at 80°K and the results were interpreted in terms of an "elastic string" dislocation mechanism and a dislocation motion mechanism based on the movement of kinks.
TL;DR: In this article, a model incorporating viscous damping of dislocations in subbarrier motion was proposed, and it was shown that the elastic precursor of the shock wave as it travels is due primarily to stress relaxation resulting from the motion of these dislocation.
Abstract: 1
The experimental damping of shock waves in iron can be described well with a model incorporating viscous damping of dislocations in subbarrier motion; it follows that the damping of the elastic precursor of the shock wave as it travels is due primarily to stress relaxation resulting from the motion of these dislocations
2
The ratio of the constant B characterizing the viscous damping of dislocations to the reduced density N of mobile dislocations which is found from the damping of an elastic shock wave is close to the value of this ratio found from the damping of ultrasound Accordingly, experiments involving the damping of elastic shock waves may be considered an independent source of B/N values
01 Feb 1970
TL;DR: In this article, the authors measured the material damping of fiberglass and boron-reinforced composites and found that the damping values for the unidirectional fiberglass composite specimens had approximately the same magnitude as those for the aluminum specimens.
Abstract: : The experimental techniques developed to measure the material damping of FRP were exponential decay of a vibrating beam (free- ree mode) and forced vibration of double cantilever beam. By using Zener's anelastic damping values were calculated and compared with experimental damping values. Good agreement was achieved. The experimental techniques were then applied to FRP and boron-reinforced composites. It was found that damping values for the unidirectional fiberglass and boron composite specimens had approximately the same magnitude as those for the aluminum specimens. However, variations in fiber orientation produced a significant increase in damping coefficients. Also, the introduction of air damping produced an increase in the observed value of material damping. The parameters of stree level and frequency were controlled, and the effect of these parameters ont he values of material damping and dynamic modulus was observed and recorded.