scholarly journals The Scattering of Phonons by Infinitely Long Quantum Dislocations Segments and the Generation of Thermal Transport Anisotropy in a Solid Threaded by Many Parallel Dislocations

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1711
Author(s):  
Fernando Lund ◽  
Bruno Scheihing-Hitschfeld
Keyword(s):  
Elastic Waves ◽  
Thermal Transport ◽  
Dislocation Line ◽  
Canonical Quantization ◽  
Angle Of Incidence ◽  
Coupling Constant ◽  
Line Configuration ◽  
Straight Line ◽  
Quantum Dislocations ◽  
Dynamic Dislocation

A canonical quantization procedure is applied to the interaction of elastic waves—phonons—with infinitely long dislocations that can oscillate about an equilibrium, straight line, configuration. The interaction is implemented through the well-known Peach–Koehler force. For small dislocation excursions away from the equilibrium position, the quantum theory can be solved to all orders in the coupling constant. We study in detail the quantum excitations of the dislocation line and its interactions with phonons. The consequences for the drag on a dislocation caused by the phonon wind are pointed out. We compute the cross-section for phonons incident on the dislocation lines for an arbitrary angle of incidence. The consequences for thermal transport are explored, and we compare our results, involving a dynamic dislocation, with those of Klemens and Carruthers, involving a static dislocation. In our case, the relaxation time is inversely proportional to frequency, rather than directly proportional to frequency. As a consequence, the thermal transport anisotropy generated on a material by the presence of a highly-oriented array of dislocations is considerably more sensitive to the frequency of each propagating mode, and, therefore, to the temperature of the material.

A computer program for the application of Zoeppritz's amplitude equations and Knott's energy equations

1976 ◽  
Vol 66 (6) ◽  
pp. 1881-1885 ◽  
Author(s):  
G. B. Young ◽  
L. W. Braile
Keyword(s):  
Computer Program ◽  
Elastic Waves ◽  
Displacement Amplitude ◽  
Plane Interface ◽  
Angle Of Incidence ◽  
Amplitude Equations ◽  
Elastic Solids ◽  
Displacement Potential ◽  
Energy Equations ◽  
Sample Case

abstract A computer program is presented which calculates Zoeppritz's displacement amplitude coefficients, displacement potential coefficients, and Knott's energy coefficients for plane harmonic elastic waves of P or SV type incident on a plane interface between two isotropic, homogeneous elastic solids. A discussion of these three basic types of coefficients is included. Results of applying the program to a sample case are presented in the form of a graph of the energy coefficients computed for all possible wave types and over a range of angle of incidence of 0° to 90°.

scholarly journals Analisis cycle time proses perakitan senjata di PT Pindad (Persero)

2021 ◽  
Vol 13 (2) ◽  
pp. 159
Author(s):  
Fandi Achmadi ◽  
Budi Harsanto ◽  
Akhmad Yunani
Keyword(s):  
Cycle Time ◽  
Assembly Line ◽  
Scientific Literature ◽  
Defense Industry ◽  
Cycle Times ◽  
Line Configuration ◽  
Straight Line ◽  
Takt Time ◽  
Potential Methods ◽  
Almost All

This paper aims to analyze the cycle time of the assembly line of one of the weapons products at PT. Pindad (Persero) and to explore the effective methods to improve its performance. The method used is a quantitative analysis of assembly data involving 155 components and 56 tasks distributed over 43 work stations, accompanied by document analysis, especially on scientific literature, to elaborate various appropriate methods to become solutions to the problems encountered. The results show that almost all workstations had a cycle time greater than the takt time. It is also known that there is an imbalance of existing workstations, with the lightest workload lasting 67 seconds while the largest workload lasting 253 seconds. The results of the elaboration of the literature show that several potential methods can provide solutions to the problems encountered by considering the characteristics of the assembly line with a straight-line configuration. This study contributes to the literature by analyzing cycle times and assembly line balances in the defense industry relatively rarely studied in Indonesia. 

Reflection of elastic waves from a linear transition layer

1966 ◽  
Vol 56 (2) ◽  
pp. 511-526
Author(s):  
Ravindra N. Gupta
Keyword(s):  
Plane Wave ◽  
Material Properties ◽  
Transition Layer ◽  
Elastic Waves ◽  
Wave Reflection ◽  
Reflection Coefficients ◽  
Angle Of Incidence ◽  
Arbitrary Angle ◽  
S Wave ◽  
Incidence Plane

abstract A separation of P- and S-wave potentials is achieved for an inhomogeneous medium in which density is constant and Lame's parameters, λ and μ, are assumed to vary as λ/λ1 = μ/μ1 = (1 + bz)2 where λ1, μ1 and b are constants. The resulting equations are solved for an arbitrary angle of incidence. Plane wave reflection coefficients are obtained for the situation when the material mentioned above forms a transition layer between two homogeneous, elastic half-spaces. First and/or second-order discontinuities in material properties are permitted at the boundaries of the transition layer. Some numerical results are given.

THE REFLECTION OF ELASTIC WAVES FROM TRANSITION LAYERS OF VARIABLE VELOCITY

Geophysics ◽  
1937 ◽  
Vol 2 (4) ◽  
pp. 357-363 ◽  
Author(s):  
Alfred Wolf
Keyword(s):  
Elastic Constants ◽  
Elastic Waves ◽  
Wave Length ◽  
Continuous Functions ◽  
Angle Of Incidence ◽  
Variable Velocity ◽  
Transition Layers ◽  
Coefficient Of Reflection ◽  
Continuous Waves ◽  
Explicit Formulae

Elastic waves are reflected not only from discontinuities in the medium in which they are propagated, but also from transition layers in which the elastic constants are continuous functions of position; the coefficient of reflection is then a function of wave length. Section 1 of this paper gives explicit formulae for the coefficient of reflection of continuous waves from such a layer, at vertical incidence. In Section 2 the manner of variation of the coefficient of reflection with the angle of incidence is discussed qualitatively. Finally, in Section 3, the shape of a pulse reflected from a transition layer is determined.

Reflection of elastic waves at the boundary with the specified stresses

2021 ◽  
pp. 52-59
Author(s):  
N.B. Chertova ◽  
◽  
Yu.V. Grinyaev ◽  
Keyword(s):  
Free Surface ◽  
Elastic Waves ◽  
Reflection Coefficients ◽  
Angle Of Incidence ◽  
Transverse Waves ◽  
Longitudinal And Transverse Waves ◽  
Tangential Stresses ◽  
Wave Parameters ◽  
Strain Components ◽  
Analytical Expressions

The problem of elastic waves reflection at the boundary at given constant stresses is considered. Provided that the reflection laws are fulfilled, analytical expressions are obtained for the reflection coefficients of longitudinal and transverse waves, which allow us to determine the deformations amplitudes at the boundary. The dependences of the reflections coefficients and strain components at the boundary on the angle of incidence of the wave are calculated at nonzero values of normal and tangential stresses at the boundary and the specified wave parameters. The obtained results are analyzed and compared with the known results for the free surface.

ULTRASOUND AS A PROBE OF PLASTICITY? THE INTERACTION OF ELASTIC WAVES WITH DISLOCATIONS

2009 ◽  
Vol 19 (08) ◽  
pp. 2765-2781 ◽  
Author(s):  
AGNES MAUREL ◽  
VINCENT PAGNEUX ◽  
FELIPE BARRA ◽  
FERNANDO LUND
Keyword(s):  
Elastic Wave ◽  
Elastic Waves ◽  
Plane Waves ◽  
Dislocation Line ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Dislocation Segment ◽  
Plastic Behavior ◽  
Line Segments

An overview of recent work on the interaction of elastic waves with dislocations is given. The perspective is provided by the wish to develop nonintrusive tools to probe plastic behavior in materials. For simplicity, ideas and methods are first worked out in two dimensions, and the results in three dimensions are then described. These results explain a number of recent, hitherto unexplained, experimental findings. The latter include the frequency dependence of ultrasound attenuation in copper, the visualization of the scattering of surface elastic waves by isolated dislocations in LiNbO 3, and the ratio of longitudinal to transverse wave attenuation in a number of materials. Specific results reviewed include the scattering amplitude for the scattering of an elastic wave by a screw, as well as an edge, dislocation in two dimensions, the scattering amplitudes for an elastic wave by a pinned dislocation segment in an infinite elastic medium, and the wave scattering by a sub-surface dislocation in a semi-infinite medium. Also, using a multiple scattering formalism, expressions are given for the attenuation coefficient and the effective speed for coherent wave propagation in the cases of anti-plane waves propagating in a medium filled with many, randomly placed screw dislocations; in-plane waves in a medium similarly filled with randomly placed edge dislocations with randomly oriented Burgers vectors; elastic waves in a three-dimensional medium filled with randomly placed and oriented dislocation line segments, also with randomly oriented Burgers vectors; and elastic waves in a model three-dimensional polycrystal, with only low angle grain boundaries modeled as arrays of dislocation line segments.

scholarly journals Reflection and transmission of elastic waves at viscous liquid/micropolar elastic solid interface

2001 ◽  
Vol 26 (11) ◽  
pp. 685-694 ◽  
Author(s):  
Rajneesh Kumar ◽  
Sushil K. Tomar
Keyword(s):  
Viscous Liquid ◽  
Half Space ◽  
Incident Wave ◽  
Elastic Waves ◽  
Elastic Solid ◽  
Specific Model ◽  
Angle Of Incidence ◽  
Amplitude Ratios ◽  
Reflection And Transmission ◽  
Special Case

Amplitude ratios of various reflected and transmitted elastic waves from a plane interface separating a viscous liquid half-space and a micropolar elastic solid half-space, are obtained in two cases (i) when longitudinal wave propagating through the solid half-space is made incident at the interface and (ii) when “coupled-wave” propagating through the solid half-space is made incident at the interface. These amplitude ratios have been computed numerically for a specific model and results obtained are presented graphically. It is found that these amplitude ratios depend on the angle of incidence of the incident wave and the effect of viscosity of the liquid on amplitude ratios is noticed. The problem studied by Tomar and Kumar (1995) has been reduced as a special case of our problem.

Scattering of plane elastic waves at rough surfaces. I

1962 ◽  
Vol 58 (1) ◽  
pp. 136-157 ◽  
Author(s):  
Iya Abubakar
Keyword(s):  
Elastic Waves ◽  
Angle Of Incidence ◽  
Dimensional Problem ◽  
Irregular Boundary ◽  
Periodic Surface ◽  
Reflected Waves ◽  
Diffracted Waves ◽  
Incident Waves ◽  
Phase Angles ◽  
The Waves

ABSTRACTAn approximate solution of the two-dimensional problem of reflexion of plane harmonic P and S V waves by an irregular boundary is obtained using a modification of Rice's perturbation method of approximation on the assumption that the curvature of the surface is everywhere small. The case of a periodic surface is treated in more detail. It is found that the reflected waves are composed of specularly reflected waves and various diffracted waves, propagating in both horizontal directions if the wavelength of the incident waves is long compared with that of the surface. If the wavelength of incident distortional waves is long compared with that of the surface, the amplitudes of some of the scattered waves decrease exponentially with depth. In general the phases of the waves change on reflexion and the phase angles of the reflected waves are functions of the wavelength of the corrugation and the angle of incidence. It is verified, in the case of zero angle of incidence, that the energy going into the scattered radiation is obtained at the expense of the energy of the specularly reflected waves.

Thermal Transport Along the Dislocation Line in Silicon Carbide

2014 ◽  
Vol 113 (12) ◽  
Author(s):  
Yuxiang Ni ◽  
Shiyun Xiong ◽  
Sebastian Volz ◽  
Traian Dumitricǎ
Keyword(s):  
Silicon Carbide ◽  
Thermal Transport ◽  
Dislocation Line

scholarly journals Centrifugal acceleration in the isotropic photon field

2017 ◽  
Vol 26 (11) ◽  
pp. 1750135 ◽  
Author(s):  
G. G. Bakhtadze ◽  
V. I. Berezhiani ◽  
Z. Osmanov
Keyword(s):  
Drag Force ◽  
Acceleration Process ◽  
Centrifugal Acceleration ◽  
Photon Field ◽  
Drag Forces ◽  
Line Configuration ◽  
Curved Trajectories ◽  
Straight Line ◽  
Field Lines ◽  
Dynamics Of Particles

In this paper, we study centrifugal acceleration of particles moving along a prescribed rotating curved trajectories. We consider the physical system embedded in an isotropic photon field and study the influence of the photon drag force on the acceleration process. For this purpose, we study three major configurations of the field lines: the straight line, the Archimede spiral and the dipolar field line configuration. By analyzing dynamics of particles sliding along the field lines in the equatorial plane, we have found several interesting features of motion. In particular, it has been shown that for rectilinear field lines, the particles reach the light cylinder (area where the linear velocity of rotation exactly equals the speed of light) zone relatively slowly for bigger drag forces. Considering the Archimedes’ spiral, we have found that in cases when the field lines lag behind the rotation, the particles achieve the force-free regime of dynamics regardless of the drag force. Unlike this scenario, when the spiral is oriented in an opposite direction, the particles do not reach the force free regime, but tend to stable equilibrium locations.

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