Influence Of Elastic Stresses Research Articles

Effect of operational factors on magnetoacoustic emission of low-carbon steels

The features of magnetoelastic acoustic emission (MAE) generation in the low-carbon (ferritic-pearlitic) steels during their magnetization by an external quasi-static magnetic field are investigated. The influence of elastic stresses, plastic deformations, volume damage of the material, heat treatment as well as the carbon content in iron alloys and the volume of remagnetization on the sum of the MAE signals amplitudes is established. An increase of the magnetization volume and heat treatment lead to an increase of the sum of the MAE signals amplitudes. The other factors cause its decrease compared to the state of supply of the ferromagnet. The obtained results are important for the construction of methods for assessing the local degradation of equipment materials of pipeline networks.

Phase Transitions in Bismuth-Containing Elastostressed AlGaInSbBi–InSb Heterosystems

The specific features of phase transitions in elastostressed Al–Ga–In–Sb–Bi heterosystems and In–Sb–Bi and Al–In–Bi subsystems are discussed. The isotherms of this heterosystem and its subsystems are studied in the temperature range 653–923 K. The critical temperatures and the coordinates of the critical points of the spinodal decomposition of the AlGaInSbBi solid solution have been determined, taking into account the coherent deformation energy. The influence of elastic stresses on the thermodynamic behavior of the AlGaInSbBi–InSb heterosystem is studied.

Влияние упругих напряжений на формирование осевых гетеропереходов в трехкомпонентных нитевидных нанокристаллах A-=SUP=-III-=/SUP=-B-=SUP=-V-=/SUP=-

The influence of elastic stresses on the formation of axial heterojunctions in ternary III-V nanowires was theoretically investigated. The composition profiles of InAs/GaAs axial heterojunction in self-catalyzed GaxIn1-xAs nanowires were obtained. It was shown that the InAs/GaAs heterojunction width amounts to tens of monolayers and increases with the increase of the nanowire radius due to elastic stresses. The elastic stress relaxation on nanowire sidewalls does not lead to the presence of miscibility gap in GaxIn1-xAs system at typical growth temperature (about 450ºC) and nanowire radius above 5 nm.

Influence of elastic stresses on the vapor-solid-solid growth mechanism of Au-catalyzed GaAs nanowires

Influence of elastic stresses on the vapor-solid-solid growth mechanism of Au-catalyzed GaAs nanowires is studied. The elastic energy of the triangle-shaped island formed on the catalyst-nanowire interface is calculated. It is shown that the nucleation time of the triangle-shaped island is several times higher than that of the disk-shaped island in the case of nucleation of semi-coherent islands. The contribution to the free energy of island formation from the formation of island side walls is higher for the triangle-shaped island, although, its contribution from the elastic energy is lower when islands nucleate at the catalyst free surface.

Influence of elastic stresses and temperature on the dislocation unpinning from the stoppers in KCl crystals

Influence of elastic stresses and temperature on the dislocation unpinning from the stoppers in KCl crystals

Influence of elastic stresses on electromagnetic-acoustic transformation in nickel, iron-nickel alloys, and permendur

It has been experimentally established that the sign of the change in the efficiency of electromagnetic-acoustic transformation under elastic tension is determined by the sign of the saturation magnetostriction and depends on the magnetic state of a ferromagnet. It is shown that, after annealing, as a result of relaxation of internal stresses, both the transformation efficiency and its sensitivity to applied stresses substantially increase. Model concepts are presented that account for the experimental dependences.

Influence of segregation effects on the electroluminescence spectra of InGaAs/GaAs quantum well heterostructures grown by H-MOVPE

Surface segregation during epitaxial growth of stressed InGaAs/GaAs quantum-well heterostructures significantly distorts the nominal concentration profile of quantum wells. The consideration of the effect for growth conditions and elastic stresses appearing during epitaxy on segregation made it possible to simulate the concentration profile with a high accuracy and to calculate the electroluminescence wavelength of actual InGaAs/GaAs heterostructures with quantum wells. It was shown that the observed effect of the long-wave-length shift for the interband transition wavelength in the important case of heterostructures with two neighboring quantum wells is caused by the influence of elastic stresses during growth.

Effect of elastic stresses on the differential magnetic permeability of amorphous ferromagnetic wires in a broad frequency range

The effect of elastic mechanical stresses on the field dependence of the differential magnetic permeability (DMP) of low-magnetostriction amorphous wires of Co66Fe4Nb2.5Si12.5B15 and Co66Fe4Ta2.5Si12.5B15 compositions has been studied in the range of magnetic field frequencies from 1 kHz to 10 MHz. The influence of elastic stresses on the DMP of amorphous ferromagnetic wires is frequency-dependent, the most significant effects being observed above 100 kHz.

Self-Organization of Nanoislands on the Surface of Silicon and Gallium Arsenide Single Crystals Stimulated by Spatially Periodic Laser Radiation Fields

Four interfering laser beams acting upon the surface of silicon and gallium arsenide single crystals stimulate the self-organization of nanoislands, which is manifested by the development of processes controlling the size of islands in a two-dimensional periodic structure formed on the sample surface. The influence of the polarization of interfering beams on the character of this self-organization has been studied. Islands with lateral dimensions from 60 to 100 nm and a height of 6–12 nm have been obtained. The lateral dimensions of nanoislands are 5–10 times smaller than the period of a standing wave of the laser radiation field, which is explained by the influence of elastic stresses developed at the crystal surface.

The influence of elastic stresses during growth of (Al)GaAs/InGaAs/(Al)GaAs quantum well heterostructures on indium distribution

The experimental and calculation data on indium distribution in (Al)GaAs/InGaAs/(Al)GaAs quantum well (QW) structures are presented. Experimental examination revealed increase of In concentration in the growth direction in single QW and relative shift of composition in close-spaced multiple QWs. The results of calculation based on consideration of elastic strain energy contribution to the free energy of mixing are in good agreement with experimental data and testify that the elastic stresses give essential contribution in the observed effect.

On the Statistics of Nucleation of 3D Coherent Islands in Heteroepitaxy from a Molecular Beam

Within the framework of the cell method, the statistics of nucleation on the vertex of a 2D island is analyzed considering the influence of elastic stresses on the bond energy of an atom in a disruption. It is shown that elastic stresses at high temperatures may decrease the nucleation time as the temperature increases and the growth rate decreases. The results obtained agree qualitatively with the experimental data on the formation of 3D coherent islands in heteroepitaxy of semiconductors in molecular-beam epitaxy systems.

Formation of multilayer strained-layer heterostructures by liquid epitaxy. I. Theoretical aspects of the problem and mathematical model

Problems concerned with the formation of multilayer strained-layer heterostructures by “capillary” liquid-phase epitaxy with forced hydraulic replacement of the solutions in the growth channel are analyzed. It is shown for short contact times between the solutions and the crystallization surface that the character of their flow in the channel plays an important role in the achievement of uniformity in the physical characteristics of the layers grown. Theoretical estimates of the hydrodynamic stability of solutions moving in narrow channels are performed for several III-V systems. A mathematical model, which permits simulation of the conditions under which strained-layer heterostructures are fabricated, is developed. It takes into account diffusive and convective mass transport in the liquid for various flow regimes in the capillary and the displacement of the heterogeneous equilibria in the system under the influence of elastic stresses.

Influence of elastic stresses on the character of epitaxial crystallization of (Hg, Mn)Te

Available experimental data on the composition and conditions for crystallization of semiconductor Hg1−zMnzTe solid-state solutions epitaxially grown on Cd(Zn)Te substrates reveal a number of peculiarities, which indicate that the substrate strongly affects the character of crystallization of the solid phase. In this paper we discuss data on liquid-phase epitaxy of Hg1−zMnzTe which suggest the possibility that elastic stresses caused by the mismatch between the crystal lattice parameters of the substrate and the epitaxial layer can influence the composition and conditions for crystallization of these layers. An important tool in our investigation is a thermodynamic analysis of the metastable equilibrium between the stressed solid phase and the supersaturated solution of components.

Influence of elastic stresses on the capillary breakup of jets of dilute polymer solutions

The capillary breakup of thin free jets of dilute polymer solutions is investigated theoretically. The evolution of the jet surface shape in the nonlinear stage of deformation, when elastic effects are important, is described in the framework of a quasi-one-dimensional description. The initial tension of the jet is shown to have a decisive influence on the breakup dynamics. The delay in breakup due to the orientation and stretching of the polymer coiled macromolecules in the initial section of the jet is determined.

Temperature dependence of resistance to small plastic deformations of spring steels and alloys

1. For small plastic deformation the materials investigated are characterized by the general rules governing deformation of polycrystalline materials. It develops in stages. At the transition from the first stage to the second the coefficient of hardening changes by a jump. The size of the jump characterizes the sensitivity of the material to overloads. 2. The anomalous temperature dependence of the flow stress for steel 12Kh18N10T is associated with the martensitic transformation in the low-temperature range under the influence of elastic stresses, and in alloys 67KN5B and 131 with the precipitation of phases (CoNi)3Nb with ordering of the Ll2 type and Ni3Al, respectively.

Influence of elastic stresses on dynamic response of iron-nickel films

Influence of elastic stresses on dynamic response of iron-nickel films

Ferromagnetic resonance in polycrystalline ferrites with high magnetic anisotropy

The ferromagnetic resonance absorption line is computed in polycrystalline ferrites in the “independent grain” approximation taking account of the magnetic crystallographic and magnetostriction anisotropies. The results obtained show that the influence of elastic stresses on the shape of the absorption line is analogous to the effect of the magnetic crystallographic anisotropy.