Energy of the elastic loading of anharmonic solids

This paper reports on the results of measurements of changes in the temperature of a solid under the adiabatic elastic loading (thermoelastic effect), the coefficient of thermal expansion, and the Young’s modulus of a rigid-chain vitrified polymer, namely, polyimide. It has been found that there are differences in the sign and magnitude of the changes in the energy of thermal origin in samples and the work of the external force. The energy of the thermoelastic effect has been explained in terms of the influence exerted by the anharmonic expansion of a solid, with the separation of the quasi-static potential and dynamic components of the thermal energy of the solid. The loading with an external force causes a redistribution of the thermal energy. A change in the temperature of the solid corresponds to a change in the dynamic component. An energy analysis of the adiabatically loaded anharmonic oscillator has confirmed the conclusion regarding the mechanism of energy transfer and revealed that, under loading, there is a redistribution of the kinetic and potential components of the internal energy of the oscillator.     

Energetics of the thermoelastic effect in solids

The dependence of the temperature on the external adiabatic deformation is determined for a one-dimensional model of a solid — chains of atoms with an anharmonic interaction. The resulting dependences of the average kinetic and potential components of the internal energy on this deformation are compared with a model of adiabatic loading of a single oscillator. Fiz. Tverd. Tela (St. Petersburg) 40, 1548–1551 (August 1998)     

Saturation of the all-optical Kerr effect in solids

We discuss the influence of the higher-order Kerr effect (HOKE) in wide bandgap solids at extreme intensities below the onset of optically induced damage. Using different theoretical models, we employ multiphoton absorption rates to compute the nonlinear refractive index by a Kramers-Kronig transform. Within this theoretical framework we provide an estimate for the appearance of significant deviations from the standard optical Kerr effect predicting a linear index change with intensity. We discuss the role of the observed saturation behavior in practically relevant situations, including Kerr lens mode-locking and supercontinuum generation in photonic crystal fibers. Furthermore, we present experimental data from a multiwave mixing experiment in BaF2, which can be explained by the appearance of the HOKE.     

Energy balance in deformation mechanics of solids at low temperatures

The model of a solid in the form of an ensemble of independent anharmonic oscillators arranged in a uniform stress field has been considered to analyze the energy balance during adiabatic mechanical loading of a solid at low temperatures. Oscillator elongation is determined as the average over the ensemble, and a part of its energy is matched to this quantity. This part has the physical meaning of the mechanical energy of sample deformation and becomes a part of the energy balance upon deformation. After averaging, the uniform force field is replaced by the resultant force associated with the average deformation. Another component of the balance at low temperatures is the energy of zero-point vibrations of oscillators. Thus, upon mechanical deformation of a solid, the energy exchange occurs between two scale levels: the atomic vibration energy at a microlevel and the macroscopic deformation energy of the sample as a whole.     

Photothermoacoustic effect in solids with piezoelectric detection

The photothermoacoustic effect in solids with piezoelectric signal detection is investigated theoretically and experimentally. Analytical expressions are found for the amplitude and phase shift of the photothermoacoustic signal as a function of the thicknesses of the sample and piezoelectric transducer, the modulation frequency, and the material constants of the structure. A method is proposed for detecting the signal using a compound piezoelectric transducer. It is shown for a bilayer piezoelectric transducer that the reduced Young’s modulus and the thermal diffusion coefficient of the experimental object can be found from the amplitude-frequency and phase-frequency curves. Zh. Tekh. Fiz. 69, 1–5 (December 1999)     

Energy streamlines for qualitative inverse scattering in fluids and solids

In time-harmonic acoustic fields, energy streamlines are defined as the integral curves of the power-flux density vector, averaged over a period. They provide a tool to visualize the details of propagation of energy. After reviewing the role of energy streamlines in the linear sampling method for acoustic inverse scattering, this work formulates a physical interpretation of the same qualitative method in the case of an isotropic homogeneous solid matrix. Specifically, it is shown that the linear sampling method results from conservation of energy along streamline tubes of energy flow associated with elastic waves.     

Energy spectra of light ions backscattered from random solids

A scheme for the calculation of energy spectra of ions backscatterred from random solids is proposed for the energy region where multiple collisions dominate. Calculations are performed for light ion bombardment of heavy targets, which is a case of special interest for the plasma-well interaction in fusion reactors. Examples of spectra obtained for protons incident on a Cu target are presented. A maximum in the spectra is found in accordance with measurements. The position of the maximum seems to vary slowly with the initial ion energy.     

Hall effect in superionic solids of nonstoichiometric composition

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 61–64, August, 1991.     

Thermal effect and equation of state in solids

In the present paper, an attempt has been made to include the thermal effect into an isothermal equation of state using the Debye approximation representing volume as a function of pressure. The calculations are done in case of NaCl, CsCl, Mo, and W. The present calculations are in good agreement with the reported results.     

Long-range effect under low-intensity irradiation of solids

Experimental results of the study of long-range low-intensity irradiation with light effect on the microhardness of silicon plates and aluminum foils (including the irradiation of aluminum/silicon stacks) are presented. These results for silicon agree with the data on irradiation effect on a system of microdefects. Some results on the small-dose long-range effect on the above mentioned materials are also given. The results are discussed using a model of the effect of radiation-induced acoustic waves on defects in solids.     

Non-parabolic effect for femtosecond laser-induced ultrafast electro-absorption in solids

A theoretical study for femtosecond laser-induced ultrafast electro-absorption of bulk solids is presented. Our numerical results show that, in the case of low intensity of the pump laser where the interaction between the pump laser and solids is in the multi-photon regime, the energy band of solids can be approximately taken as a parabolic band and electro-absorption spectrums from the parabolic band and real band are nearly the same. While, in the case of high intensity where the interaction is in the tunneling regime, spectrums from the parabolic band and real band are quite different.The physical mechanism for the difference in the tunneling regime is found. We find that the non-parabolic parts of the real energy band and Bragger scattering of electrons near the first Brillouin zone boundaries, which are neglected in previous studies, strongly influence the electro-absorption spectrum in the tunneling regime. These two physical processes cause the difference of spectrums. Our theoretical results are in accordance with the experiment result.     

Trigger effect of weak vibrations in solids (rocks)

The effect of weak low-frequency vibrations on the process of microfailure was studied. Cylindrical rock samples were subjected to uniaxial compression, during which low-frequency vibrations were periodically applied. The vibrations were weak as compared to the compressive load. Acoustic emission was monitored. The acoustic-emission signal was found to increase sharply after a delay when vibrations were applied for a short time (100–200 s). This effect was explained using the concentration criterion for the formation and development of a site of failure.     

Universal additive effect of temperature on the rheology of amorphous solids

Extensive measurements of macroscopic stress in a 2D Lennard-Jones glass, over a broad range of temperatures (T) and strain rates (γ), demonstrate a very significant decrease of the flowing stress with T, even much below the glass transition. A detailed analysis of the interplay between loading, thermal activation, and mechanical noise leads us to propose that over a broad (γ, T) region, the effect of temperature amounts to a mere lowering of the strains at which plastic events occur, while the athermal avalanche dynamics remains essentially unperturbed. Up to the vicinity of the glass transition, temperature is then shown to correct the athermal stress by a (negative) additive contribution which presents a universal form, thus bringing support to and extending an expression proposed by Johnson and Samwer [Phys. Rev. Lett. 95, 195501 (2005)].     

Single-phonon contribution to the hopping Hall effect in amorphous solids and glasses

Full single-phonon contribution to the tensor of the electronic d.c. hopping conductivity in external magnetic field? is found and its first derivative (with respect to?) is shown to vanish at?=0. Thus the Hall mobilityμ _H is found to be proportional to the squared electron-phonon coupling constantg ² at least, in accordance with extremely low values ofμ _H in amorphous semi-conductors and glasses.     

Theoretical and experimental investigation of the photoacoustic effect in solids with residual stresses

Modern experiment and theory in the field of residual stress detection by the photoacoustic method are summarized and analyzed. A multimode approach based on the simultaneous application of several photothermal and photoacoustic methods is proposed for the study of thermal and thermoelastic effects in solids with residual stress. Some experimental results obtained within the framework of this approach for Vickers indentation zones in ceramics are presented. The effect of annealing on the photoacoustic, piezoelectric signal for ceramics and the influence of the given external loading on the behavior of the photoacoustic signal near the radial crack tips is investigated. It is experimentally shown that both compressive and shear stresses contribute to the photoacoustic signal near the radial crack tips. The model of the photoacoustic, thermoelastic effect in solids with residual stress is proposed. It is based on the modified Murnaghan model of non-linear elastic bodies, which takes into account a possible dependence of the thermoelastic constant on stress. This model is further developed to explain the photoacoustic signal behavior near the radial crack tips. It is demonstrated that this model of the photoacoustic effect agrees qualitatively with the available experimental data.     

Three equations of state for solids considering thermal effect

 The Einstein model to consider thermal effect in universal equations of state (UEOS) is modified. It is proposed that the zero-point vibration term should be deleted in a thermal UEOS, and the parameters cannot be directly taken as experimental data at a reference temperature, V_R, B_R, and , but their values at absolute zero temperature, V₀, B₀, and . An approach is proposed to solve V₀, B₀, and from V_R, B_R, and . The approaches are applied to three typical universal EOSs, including the Baonza, mGLJ and Morse EOSs. The numerical results show that the solved values of parameters are almost identical for different EOSs. And the thermo-physical properties predicted through different EOSs are almost identical at zero- and low-pressure conditions, once the same approach and input experimental data are used to solve the parameters. It is concluded that the prediction of thermo-physical properties at zero- and low-pressure conditions cannot be taken as the criteria to judge the applicability of a universal EOS.     

Third- and fourth-order constants of incompressible soft solids and the acousto-elastic effect

Acousto-elasticity is concerned with the propagation of small-amplitude waves in deformed solids. Results previously established for the incremental elastodynamics of exact non-linear elasticity are useful for the determination of third- and fourth-order elastic constants, especially in the case of incompressible isotropic soft solids, where the expressions are particularly simple. Specifically, it is simply a matter of expanding the expression for ρv(2), where ρ is the mass density and v the wave speed, in terms of the elongation e of a block subject to a uniaxial tension. The analysis shows that in the resulting expression: ρv(2) = a+be+ce(2), say, a depends linearly on μ; b on μ and A; and c on μ, A, and D, the respective second-, third, and fourth-order constants of incompressible elasticity, for bulk shear waves and for surface waves.