Showing papers on "Thermoelastic damping published in 1985"
TL;DR: In this paper, the authors evaluated stiffnesses and compliances, thermal expansion coefficients, and stress and strain averages for a fibrous composite lamina which contains a given density of open transverse cracks and is subjected to uniform mechanical loads and thermal changes.
Abstract: Overall stiffnesses and compliances, thermal expansion coefficients, and stress and strain averages are evaluated for a fibrous composite lamina which contains a given density of open transverse cracks and is subjected to uniform mechanical loads and thermal changes. The evaluation procedure is based on the self-consistent method and is similar, in principle, to that used in finding elastic constants of unidirectional com posites.
193 citations
ARCO1
TL;DR: In this paper, a numeric method has been developed to calculate thermoelastic stresses induced within elliptically shaped regions of finite thickness, and empirical equations were developed to give an approximate but convenient, explicit method for estimating induced stresses.
Abstract: This work considers thermoelastic stresses which would result from cooled regions of fixed thickness and of elliptical cross section. The stresses for an infinitely thick reservoir have been deduced from information available in public literature. A numeric method has been developed to calculate thermoelastic stresses induced within elliptically shaped regions of finite thickness. Results of these 2 approaches were combined, and empirical equations were developed to give an approximate but convenient, explicit method for estimating induced stresses. An example problem is given which shows how this theory can be applied to calculate the fracture lengths, bottom-hole pressures, and elliptical shapes of the flood front as the injection process progresses. (20 refs.)
176 citations
TL;DR: In this paper, a noncontact, full-field, stress analysis technique based on the measurement of the intensity of infra-red radiation emitted from the surface of a cyclically loaded body is applied to series of metallic specimens (including beams in bending, the ‘Brazilian’ disc, and a simple pure-shear testpiece).
Abstract: A new non-contact, full-field, stress analysis technique based on the measurement of the intensity of infra-red radiation emitted from the surface of a cyclically loaded body is applied to series of metallic specimens (including beams in bending, the ‘Brazilian’ disc, and a simple pure-shear testpiece) and critically appraised.
151 citations
TL;DR: In this paper, the authors present a thermoelastic analysis of the composite cylinder model for a undirectional composite including anisotropic fibers and an interphase region, and find the magnitude of residual thermal stresses on the micromechanics level induced by differential shrinkage between the fiber and the matrix.
Abstract: We present a thermoelastic analysis of the composite cylinder model for a undirectional composite including anisotropic fibers and an interphase region. We have found the magnitude of the residual thermal stresses on the micromechanics level induced by differential shrinkage between the anisotropic fibers and the matrix. For typical composites the largest residual stress is tension along the fiber direction, and a simple lower bound expression for this stress is given. Prediction of the magnitude of the thermal stresses requires knowledge of the thermal and physical properties of the matrix. The relevant properties for epoxy and thermoplastic matrices are discussed. The magnitude of the residual stresses can be reduced by tailoring the interphase region, but only if the interphase region serves to reduce the temperature for the onset of stress buildup. The volume fraction dependence of the longitudinal and transverse thermal expansion coefficients of the composite is compared to analogous expressions in the literature which do not include anisotropy of the fibers.
140 citations
TL;DR: In this paper, the authors provided several simple models for the state of thermoelastic stress in a young oceanic lithosphere, taking into account a comparison of the predictions of these models with the characteristics of near-ridge earthquakes.
Abstract: Thermoelastic or thermal stress is a potentially important contributor to the state of stress in the oceanic lithosphere. The present paper provides several simple models for the state of thermoelastic stress in a young oceanic lithosphere, taking into account a comparison of the predictions of these models with the characteristics of near-ridge earthquakes. Attention is given to the characteristics of near-ridge earthquakes, sources of stress in an oceanic lithosphere, previous models of thermal stress, the calculation of thermal stress, and thermal stress models. A test is conducted of the hypothesis that thermoelastic stress is a significant component of the stress field in a young oceanic lithosphere. The considered models support the hypothesis that thermoelastic stress is a significant component of the stress field in a young oceanic lithosphere.
85 citations
TL;DR: A review of the various instability-based theories of melting with special emphasis on a particular type of instability which is both thermodynamic and elastic in nature can be found in this article.
Abstract: The various instability-based theories of melting are reviewed with special emphasis on a particular type of instability which is both thermodynamic and elastic in nature. This “thermoelastic” instability originates from a decrease in resistance to shear stress, an idea developed by Born, and is characterized by divergent coefficients of thermal expansion (α) and isothermal compressibility at the melting temperature (T m), an ideal first proposed by Herzfeld and Goeppert-Mayer (1934). Evidence is presented from the results of parameter-free equation-of- state calculations for alkali halides and from published thermal expansion results for a variety of materials, which suggests that melting in many materials may be caused by a thermoelastic instability. A study of the potential energy surface for NaF suggests a type of disorder for the liquid phase which is consistent with recent results of molecular dynamics calculations. If α diverges at Tm then the slope of the melting curve can be deduced from...
73 citations
TL;DR: In this article, an overview of the current understanding of the variables which affect the thermal stress failure of brittle structural ceramics for a variety of failure phenomena including thermoelastic instability, thermal fatigue and instantaneous thermal stress fracture, as well as stable and dynamic crack propagation.
70 citations
Abstract: In this paper, a general variational principle for the initial boundary value problem of quasi-static thermoelastic consolidation is developed by assuming infinitesimal deformation and an incompressible fluid flowing through a linearly elastic solid. By manipulating the coupling operators, an extended form of the variational pronciple is derved. The associated finite element formulation based on this principle is presented and numerical applications for plane strain thermo-elastic consolidation are revealed.
69 citations
TL;DR: In this paper, the effect of brake design and operating parameters on the maximum temperature reached was examined and the effects of hot spots being in intermittent contact due to the geometric design of the brake were discussed.
Abstract: Thermal distortion in brakes due to frictional heating causes localized contact and high temperatures (hot spots) with consequent thermal damage to the sliding components. This paper examines the effect of brake design and operating parameters on the maximum temperature reached. Previous solutions for steadystate sliding are reviewed and the effects of hot spots being in intermittent contact due to the geometric design of the brake are discussed. Approximate solutions for transient thermoelastic contact are extended to the case of uniform deceleration to determine the duration of the stop for which thermoelastic effects will be significant. If the stop is sufficiently slow for hot spots to develop, the temperatures will generally be high. However, high temperatures are also reached in sufficiently rapid stops due to the high rate of energy dissipation. An optimum is found between these extremes.
68 citations
TL;DR: In this article, the propagation of generalized thermoelastic waves in transversely isotropic media has been investigated and the basic equations have been solved by a general method after decoupling the SH wave, which is not affected by thermal variations and is independent of the rest of the motion.
Abstract: In this paper the propagation of generalized thermoelastic waves in transversely isotropic media has been investigated. The basic equations have been solved by a general method after decoupling the SH wave, which is not affected by thermal variations and is independent of the rest of the motion. The discussion of the frequency equation reveals that in general there are three distinct waves in transversely isotropic media. The particle paths during the motion are found to be elliptic. The inclinations of the major axes with wave normal and the eccentricities of elliptical paths have been determined. The results have been verified numerically and are represented graphically for a single crystal of zinc in the case of waves of assigned frequency.
53 citations
TL;DR: In this article, it was shown that in linear homogeneous isotropic thermoelasticity with two relaxation times the disturbances produced by an instantaneous concentrated source of heat in an infinite region represent a wave of order n = −1 with respect to the displacement u and temperature θ, i.e., 1 * u and 1 * ǫ, where * denotes convolution with regard to time, suffer jump discontinuities across a propagating spherical surface.
Abstract: It is shown that in linear homogeneous isotropic thermoelasticity with two relaxation times the disturbances produced by an instantaneous concentrated source of heat in an infinite region represent a wave of order n = −1 with respect to the displacement u and temperature θ, i.e., 1 * u and 1 * θ, where * denotes convolution with respect to time, suffer jump discontinuities across a propagating spherical surface. Proof of the assertion is based on analysis of an exact series solution to a central initial boundary value problem of the theory. Also, closed forms of the decaying with lime displacement and temperature “amplitudes” of order 1.0 and +1 and hence closed forms of the radial and hoop-stress jumps are obtained. A way to weaken the strong discontinuity thermoelastic wave by improving the smoothness in time of the concentrated source of heat is discussed.
TL;DR: In this article, a pulsed photothermal method is proposed for the detection of delaminations in layered materials, where the surface of the material is heated by a focused laser pulse to a few degrees above the ambient temperature, and the induced thermoelastic displacement is detected by a laser interferometer.
Abstract: A pulsed photothermal method is proposed for the detection of delaminations in layered materials. The surface of the material is heated by a focused laser pulse to a few degrees above the ambient temperature, and the induced thermoelastic displacement is detected by a laser interferometer. Unbonded areas are characterized by their thermoelastic bending behavior, in addition to their thermal expansion, because of the induced temperature gradients both in the radial and axial directions. A theoretical analysis and an experimental investigation of this behavior are described in order to point out the most significant parameters. An application of the nondestructive inspection of Al‐epoxy honeycomb panels is presented.
TL;DR: In this article, short laser pulses were used for generating surface acoustic waves (SAW) on optically opaque solids via the thermo-elastic effect, and maximal efficiency was obtained when a=vRτ(vR: Rayleigh velocity, 2τ: total laser-pulse length).
Abstract: Short laser pulses were used for generating surface acoustic waves (SAW’s) on optically opaque solids via the thermoelastic effect. The spatial and temporal shapes of the laser pulses were either a spot or a line of variable total width δ=2a with a Gaussian power distribution. Maximal efficiency is obtained when a=vRτ(vR: Rayleigh velocity, 2τ: total laser‐pulse length). This condition is caused by interference effects between the individual frequency components radiating from the area of the thermoelastic source. If the intensity of the laser beam were 100% modulated at a given frequency, maximal efficiency would occur if kR=(2)1/2/a (kR: wave vector of the SAW’s).
TL;DR: In this article, a rigorous hybrid finite element procedure for the analysis of the thermoelastic problems with mixed-mode cracks is presented, in which hybrid singular elements are used around the crack-tip and high-order isoparametric regular elements are taken elsewhere.
TL;DR: In this paper, a continuum theory is presented for the prediction of the average behavior of unidirectional fiber-reinforced materials in which both constituents are thermoelastic in the linear region and thermo-inelastic in nonlinear region.
TL;DR: In this paper, a finite element formulation utilizing quadratic layer elements and linear interface elements is used to perform the analyses. And the effects of heat-transfer resistance at layer contact surfaces are illustrated through numerical examples.
TL;DR: In this article, a transient contact problem with frictional heating for two sliding halfplanes is considered, where one halfplane is slightly rounded to give a hertzian initial pressure distribution; the other is a rigid non-conductor.
TL;DR: In this article, the bending motion of the inelastic beam is put into a linear form by interpreting the nonlinear part of the operator as a fictitious temperature-moment loading, thus consistently considering the inhomogeneous character of the dynamic boundary conditions.
TL;DR: The different laser radiation interaction mechanisms are briefly discussed together with the theoretical models which explain the thermo-elastic regime as discussed by the authors, and a general survey of experimental measurements includes optical techniques and acoustic methods.
TL;DR: In this paper, a quasi-Newton method is used to select the initial point for a random jump routine to minimize the complementary strain energy, and an approximate solution for the thermoelastic response is obtained using the Rayleigh-Ritz procedure.
Abstract: A thermoelastic optimization procedure is proposed for the design of symmetric. laminated, fiber-reinforced plates. A maximum stiffness criterion is employed, wherein the ply orientations are found by minimizing the complementary strain energy. Approximate solutions for the thermoelastic response are obtained using the Rayleigh-Ritz procedure. Optimization is performed via a quasi-Newton method, with the initial point selected using a random jump routine. Numerical results are presented for simply supported plates subject to a temperature distribution that varies linearly in the thickness direction. Results are given for various composite materials, and the optimum thermoelastic solutions are compared with designs for mechanically loaded laminated plates.
Journal Article•
TL;DR: The theory of electron beam acoustic imaging with acoustic wave generation through the thermo-elastic effect, or electron thermoelastic acoustic microscopy, has been developed in three dimensions as mentioned in this paper.
Abstract: The theory of electron beam acoustic imaging with acoustic wave generation through the thermoelastic effect, or electron thermoelastic acoustic microscopy, has been developed in three dimensions. Images are created through two separate processes: acoustic wave (vibration) generation and acoustic wave transmission. Acoustic wave generation through the thermoelastic effect depends on the material’s thermal and elastic properties. Images based on these properties with resolution on the order of 5 μm is possible. The effect of imaging at different frequencies and phase angles is considered, both theoretically and experimentally, with an integrated circuit. Acoustic wave transmission affects the image by introducing vibrational patterns. This phenomenon was studied with aluminum foil. The effect of acoustic transmission on the image can also be used to detect subsurface cracks, delaminations, and voids. The detection of a delamination in glass at a depth of 25 μm is demonstrated.
TL;DR: In this article, the effects of structural and geometrical constraints on damping loss factors are investigated, and optimum conditions for the maximum damping are investigated for the stage of system design.
Abstract: The thermoelastic damping due to thermal currents and the electromagnetic damping due to electric conduction currents of vibrating solids are discussed. The effects of structural and geometrical constraints on damping loss factors are investigated. Also, optimum conditions for the maximum damping, which may be useful on the stage of system design, are investigated. It is found that damping loss factors are generally dependent upon structural and geometrical configurations. An analogy exists between thermoelastic damping and electromagnetic damping, showing Debye curves with Debye peaks. Standing transverse waves are likely to achieve larger damping than standing dilatational waves in the presence of a magnetic field. Electromagnetic damping in ferromagnetic material bodies is found to be considerable in high field. The influence of thermoelastic damping on aeroelastic stability of beam plates is investigated. This research strongly suggests that thermoelastic damping improves the aeroelastic stability of beam plates.
TL;DR: Etirage du polymere reticule par le peroxyde de decumyle, a l'etat gonfle ou mou, entre 10 and 70°C.
Abstract: Etirage du polymere reticule par le peroxyde de decumyle, a l'etat gonfle ou mou, entre 10 et 70°C
TL;DR: In this article, a treatment of a transient thermoelastic contact problem in a short-length circular cylinder, to which a heated rigid band is bonded, is presented, which may be reduced to that of solving dual-series equations.
Abstract: This paper is a treatment of a transient thermoelastic contact problem in a short-length circular cylinder, to which a heated rigid band is bonded. The problem may be reduced to that of solving dual-series equations. The solution meets the boundary conditions on both the lateral surface and the plane ends of the cylinder. The radial, hoop, and axial stresses have singularities at the end of a rigid band on the cylindrical surface.
TL;DR: In this paper, the linear Chen-Gurtin-Pipkin theory of heat conduction in a deformable material is employed to study the one dimensional problem of a homogeneous thermoelastic half space subjected to thermal and mechanical disturbances at its boundary.
Abstract: The linear Chen-Gurtin-Pipkin theory of heat conduction in a deformable material is employed to study the one dimensional problem of a homogeneous thermoelastic half space subjected to thermal and mechanical disturbances at its boundary. A ray series approach is used to generate asymptotic wavefront expansions for the temperature, strain, and stress response of the medium to the disturbances. General properties of the propagation process are obtained simply and directly. We specialize the solution to the case for which this theory reduces to that of Lord and Shulman and demonstrate that our results for this example agree with asymptotic results obtained previously by other investigators.
TL;DR: In this paper, a Q-switched, frequency doubled ruby laser has been used to generate ultrasonic transients in both metals and water, at a wavelength of 347 nm in the UV.
Abstract: A Q‐switched, frequency doubled ruby laser has been used to generate ultrasonic transients in both metals and water. The laser source delivered multimode pulses, of 30‐ns duration and energy ⩽200 mJ, at a wavelength of 347 nm in the UV. Displacements generated in metal plates were detected by wideband capacitance transducers, and compared to wave propagation theory. Thermoelastic, ablative, and modified surface sources were examined, and a good correlation between experiment and theory obtained. In addition, wideband directivity patterns in aluminum were obtained for the thermoelastic source. Thermal generation in water with a cylindrical geometry was also examined, and the expected dipolar pressure transients recorded. It was shown that their duration was a function of the multimode laser beam diameter over the 1.5‐ to 4‐mm range.
TL;DR: The temperature dependence of small degassed hamster lung strip mechanics was examined to develop insights into the molecular basis of lung elasticity, suggesting that strips behave like rubber polymers near physiological temperature.
Abstract: We examined the temperature dependence of small degassed hamster lung strip mechanics to develop insights into the molecular basis of lung elasticity Quasi-static length-tension curves of adapted
TL;DR: The photothermal beam deflection (PBD) technique as mentioned in this paper utilizes a change of refractive index of the gas surrounding a sample, and a thermoelastic deformation on the sample surface induced by the heat generated as a result of the light absorption.
Abstract: The photothermal beam deflection (PBD) technique utilizes a change of refractive index of the gas surrounding a sample, and a thermoelastic deformation on the sample surface induced by the heat generated as a result of the light absorption. The elastic property of the sample has been measured nondestructively and without contact using PBD. This technique was applied for the first time to the inspection of a dislocation existing in a GaAs semiconductor wafer.