Showing papers on "Thermoelastic damping published in 1972"
01 Mar 1972
TL;DR: In this article, a unified and rational treatment of the theory of fiber reinforced composite materials is presented, and detailed derivations of the effective elastic moduli for these materials are presented.
Abstract: A unified and rational treatment of the theory of fiber reinforced composite materials is presented. Fundamental geometric and elasticity considerations are throughly covered, and detailed derivations of the effective elastic moduli for these materials are presented. Biaxially reinforced materials which take the form of laminates are then discussed. Based on the fundamentals presented in the first portion of this volume, the theory of fiber-reinforced composite materials is extended to include viscoelastic and thermoelastic properties. Thermal and electrical conduction, electrostatics and magnetostatics behavior of these materials are discussed. Finally, a brief statement of the very difficult subject of physical strength is included.
263 citations
149 citations
TL;DR: In this paper, the authors investigated the thermally conductive instability of sliding contact for the case of a scraper or blade sliding normal to its line of contact on a semi-infinite body.
139 citations
128 citations
TL;DR: In this paper, the shape memory effect can be universally correlated with a martensitic transformation that is thermo-elastic in nature, the thermoelasticity being attributed to ordering in the parent and martensite phases.
Abstract: The shape memory effect, by which a material, apparently plastically deformed, reverts to its original shape upon heating to some higher temperature, has been reviewed and discussed from the point of view of the crystallography of martensitic transformations. Considering the general characteristics of martensitic materials that exhibit the shape memory behaviour, some phenomena peculiar to the prototype NiTi alloy are shown to have no direct relation to the shape memory. It is concluded that the shape memory effect can be universally correlated with a martensitic transformation that is thermoelastic in nature, the thermoelasticity being attributed to ordering in the parent and martensitic phases.Prerequisites for the shape memory behaviour are suggested to be: (1) that the martensitic transformation is thermoelastic; (2) that the parent and martensitic phases are ordered; and (3) that the martensite is internally twinned. The low-temperature deformation process is discussed with reference to the l...
116 citations
TL;DR: In this article, a unified theory of the effect of phonon-phonon scattering on the drag force acting upon a dislocation moving with velocity v, much less than the sound velocity, is presented.
Abstract: A unified theory of the effect of phonon‐phonon scattering on the drag force Bv acting upon a dislocation moving with velocity v, much less than the sound velocity, is presented. A formalism is developed in terms of a frequency‐ and wave‐vector‐dependent bulk viscosity. Thermoelastic damping, phonon viscosity, phonon scattering, and, in the case of oscillatory motion, reradiation damping are all included in this framework. It is shown that the dominant mechanism is that resulting from phonon scattering and gives rise to the form BS=β [k2R(0)/θΩa2]J5(T/θ) for a straight dislocation. Here R(0)=WDT2/Λ)T→0, where WD is the dislocation contribution to the phonon component of the thermal resistance, Λ the dislocation density, Ωa the atomic volume, κ is the Boltzmann constant, and T and θ the ambient and Debye temperatures, respectively. The function J5(x)5=(x)5/5!)∫ 01/xx5ex(ex−1)−2dx, and the numerical constant β is estimated to be 1.2×104. The physical processes underlying all the above mechanisms are explore...
80 citations
TL;DR: In this paper, an exact solution of the frequency equation for plane thermoelastic waves is given and the range of validity of approximate solutions for large and small frequencies is also given and numerical verification is presented.
65 citations
TL;DR: In this article, the influence of the reference geometry and the related aspects of material symmetry restriction on the response of thermoelastic shells is discussed in the case of isotropic shells which may be of variable thickness in a reference state.
Abstract: Within the scope of the nonlinear theory of an elastic Cosserat surface, this paper is mainly concerned with the influence of the reference geometry and the related aspects of material symmetry restriction on the response of thermoelastic shells. The significance of the effect of the reference geometry is discussed in the case of isotropic shells, which may be of variable thickness in a reference state.
30 citations
TL;DR: In this paper, the room-temperature elastic constants of a pyrolytic graphite were measured by an ultrasonic transmission technique and compared with values calculated on the basis of the constant strain and constant stress models from the elastic constants.
Abstract: The room-temperature elastic constants of a pyrolytic graphite were measured by an ultrasonic transmission technique and compared with values calculated on the basis of the constant strain and constant stress models from the elastic constants of compression-annealed pyrolytic graphite (CAPG). It was found that the constant stress model gives better agreement; and that the measured C 11 and C 44 can be bracketed by calculations with the basal plane shear constants of neutron-irradiated and unirradiated CAPG respectively as inputs, as would be expected because of the high mobility of dislocations in the basal plane. Gruneisen parameters, for sample temperatures between 80 and 300°k, were determined from measurements of inertial thermoelastic stress. Calculations from single-crystal thermal expansion and elastic constant values showed reasonable agreement with the measured parameters and indicated that the elastic constants of a given pyrolytic graphite, being extremely structure sensitive, can be u...
26 citations
TL;DR: In this paper, an analysis for one-dimensional wave propagation in composite materials is presented, where the effects of geometric dispersion and spatial attenuation are included through the introduction of a complex wave number.
Abstract: : An analysis is presented for one-dimensional wave propagation in composite materials. The effects of geometric dispersion and spatial attenuation are included through the introduction of a complex wave number. This type of problem arises when the constituents of the composite are viscoelastic or when heat is generated due to thermoelastic coupling or scattering from inclusions occurs. The analysis is restricted to the low-frequency portion of the response and is therefore valid only in the far field. (Author-PL)
25 citations
TL;DR: In this article, a uniqueness theorem for nonhomogeneous and anisotropic shells undergoing small motions (and small temperature change) superposed on a large deformation was obtained without the use of definiteness assumption for the free energy.
Abstract: Within the scope of the non-isothermal theory of an elastic Cosserat surface and for a system of linear equations characterizing the initial mixed boundary-value problems of thermoelastic shells, a uniqueness theorem is obtained without the use of definiteness assumption for the free energy. The theorem holds for nonhomogeneous and anisotropic shells undergoing small motions (and small temperature change) superposed on a large deformation.
TL;DR: In this article, a damping addition employing several thin viscoelastic sheets and thin metallic layers was proposed to increase the damping of thin simply supported square plates, and an experimental investigation of the effectiveness of such damping additions is also reported.
Abstract: An analysis is given for a damping addition employing several thin viscoelastic sheets and thin metallic layers. The damping layers are alternated with the constraining layers, which are segmented and are not anchored to the base plate. The effectiveness of such additions in increasing the damping of thin simply supported square plates is evaluated and methods for optimizing the design are considered. An experimental investigation of the effectiveness of such damping additions is also reported. Additions weighing a few percent of the weight of the base plate were found to produce substantial increases in the damping of the system. A nonoptimal design was found to produce less, but still substantial, damping.
TL;DR: In this article, the creep rate of polyethylene following an imposed temperature change is observed to exceed the rate predicted theoretically, attributed to thermoelastic stresses generated by the anisotropic thermal expansion of the polymer crystals.
Abstract: The creep rate of polyethylene following an imposed temperature change is observed to exceed the rate predicted theoretically. The enhancement of creep rate is attributed to thermoelastic stresses generated by the anisotropic thermal expansion of the polymer crystals.
TL;DR: In this paper, an approximate self-consistent damping rate for a finite amplitude wave is obtained in the limit of γLτ0≫1 and τ0≪1, where τ0 is the bounce period of the particles in the wave potential well.
Abstract: An approximate self‐consistent damping rate for a finite amplitude wave is obtained. In the limit of γLτ0≫1 and γLτ0≪1, where γL is the linear Landau damping coefficient and τ0 is the bounce period of the particles in the wave potential well, the linear Landau damping rate and O'Neil damping coefficient, respectively, are recovered from the generalized result, which is in the form of an integral equation. By the technique of numerical iteration, the damping coefficients for different values of γLτ0 ranging from 0.1 to 1 have been obtained. Damped wave amplitudes are also plotted which show semiquantitative agreement with the experimental data of Malmberg and Wharton.
TL;DR: In this paper, the elastic and thermoelastic constants of cubic LiBaF3 are measured by ultrasonic methods and the results for the mean elastic stiffness and for the refractive index exceed those of LiF and BaF2.
Abstract: Abstract The elastic and thermoelastic constants of cubic LiBaF3 are measured by ultrasonic methods. As a consequence of the larger packing density which results from the higher coordination number of the Ba ions in LiBaF3 the values for the mean elastic stiffness and for the refractive index exceed those of LiF and BaF2 . A quantitative explanation of these properties is given. The values of many other properties range between those of LiF and BaF2.
TL;DR: In this paper, the authors investigated experimentally a recent model of magnetomechanical damping based on a distribution of internal stresses, verifies some predictions and extends the model.
Abstract: This work investigates experimentally a recent model of magnetomechanical damping based on a distribution of internal stresses, verifies some predictions and extends the model. Damping results are reported for cast irons and iron alloyed with silicon or germanium. As predicted, the maximum magnetomechanical damping ψmax is inversely proportional to the strain amplitude which produces ψmax. To explain the relatively slow decrease of ψmax with superimposed static shear stress or external magnetic field, the model must be modified to account for stress components or demagnetizing fields. By considering stress components along magnetization directions on opposite sides of a domain wall, we introduce a technique for describing the effect of single‐crystal and grain orientations. This description qualitatively explains why bars with random grain orientations have larger damping in bending than in torsion. Although models relating damping to magnetic properties are in‐exact, damping correlates experimentally wit...
TL;DR: In this article, the coupled thermoelastic theory of a thin plate is discussed using a perturbation method, the free vibration frequencies of plates under various boundary conditions are found.
Abstract: In this paper the coupled thermoelastic theory of a thin plate is discussed. Using a perturbation method, the free vibration frequencies of plates under various boundary conditions are found. Furthermore, a solution is given for the problem of a generally loaded thermoelastic plate and thermoelastic dissipations are shown.
TL;DR: In this article, various methods are discussed and compared for the prediction of temperature and thermoelastic stress fields in nuclear reactor fuel elements and other components due to both steady and transient non-uniform surface heat transfer.
TL;DR: In this article, the effect of internal state variables on the growth and decay properties of acceleration waves in anisotropic nonlinear thermoelastic materials was studied and sufficient conditions were given which insure the existence of a plane longitudinal acceleration wave and two transverse acceleration waves with orthogonal amplitudes.
Abstract: This work is concerned with the effect of internal state variables on the growth and decay properties of acceleration waves in anisotropic nonlinear thermoelastic materials. Sufficient conditions are given which insure the existence of a plane longitudinal acceleration wave and two transverse acceleration waves with orthogonal amplitudes.
TL;DR: In this paper, a linear two-temperature theory of thermoeleasticity is used to investigate cylindrical and spherical wave propagation emanating from a cavity, and transform methods of solution to specific boundary value problems are employed.
Abstract: A linear two‐temperature theory of thermoeleasticity is used to investigate cylindrical and spherical wave propagation emanating from a cavity. Transform methods of solution to specific boundary‐value problems are employed and interest is directed to wave speeds and traveling discontinuities. A comparison with classical one‐temperature coupled thermoelastic effects is presented.
01 Jan 1972
TL;DR: In this article, the decay of transverse vibration following an impulse load on the beams was dominated by viscous damping at low frequencies, both of which were measured on beams of various geometries.
Abstract: The damping of free-free beams vibrating in dense, still fluids has been studied experimentally. The decay of transverse vibration following an impulse load on the beams was dominated by viscous damping at low frequencies, both of which were measured on beams of various geometries. The results raise considerable question concerning the validity of measuring the damping characteristics of material samples in water. It appears that the material samples must be designed to minimize spurious fluid-damping effects, otherwise the results may be more particular to the experiment configuration than to the material itself.
TL;DR: In this paper, the transient vibration problem of beams with hysteresis damping is studied, and the mathematical solution employing the asymptotic method is given first, followed by the equivalent linear solution.
Abstract: The transient vibration problem of beams with hysteresis damping is studied. The hysteresis damping is characterized by being strain dependent, frequency independent, and having a stress‐strain loop with sharp corners. The mathematical solution employing the asymptotic method is given first, followed by the equivalent linear solution. Finally, the usefulness of the equivalent linear solution is discussed.
TL;DR: In this paper, a variable winding tension was employed to give a required initial stress distribution, which was constructed on the basis of solutions describing the loss of tension associated with winding and the softening of the resin during heat treatment.
Abstract: It is proposed to employ a variable winding tension designed to give a required initial stress distribution. The program is constructed on the basis of solutions describing the loss of tension associated with winding and the softening of the resin during heat treatment. The problems are solved in the elastic formulation. Programs are obtained for three cases: constant tension in a ring sill on the mandrel, compensation of the stresses that develop after removal from the mandrel, and compensation of the thermoelastic stresses that develop during cooling.
TL;DR: Forced longitudinal vibrations of a prismatic, slender bar with distributed quadratic damping and equivalent viscous damping are considered in this article, where the damping is linearized by equating the energies dissipated per cycle by the two types of damping.
Abstract: Forced longitudinal vibrations of a prismatic, slender bar with distributed quadratic damping and equivalent viscous damping are considered. The bar is free at one end and subjected to harmonic excitation at the other. The nonlinear differential equation with the velocity‐squared term is solved numerically by the method of characteristics. The linearized equation is solved by Laplace transforms and the solution is compared to that of the nonlinear system. The damping is linearized by equating the energies dissipated per cycle by the two types of damping. Frequency‐response curves, through the second natural mode, are given for several sets of the nonlinear and equivalent viscous damping coefficients.
TL;DR: In this article, a theoretical and experimental study of composite laminates reinforced by continuous fibers of various orientations, subjected to a uniform increase of temperature is presented, and it is shown that a warping of the cross-ply is induced, due to a thermoelastic bending-membrane coupling.