Transient response of bilayered elastic strips with interfacial diffusion and sliding in cylindrical bending

2017 ◽  
Vol 23 (5) ◽  
pp. 748-774 ◽  
Author(s):  
Xu Wang ◽  
Cuiying Wang
Keyword(s):  
Elastic Property ◽  
Lower Layer ◽  
Relaxation Times ◽  
Elastic Field ◽  
External Loading ◽  
Interfacial Diffusion ◽  
Cylindrical Bending ◽  
Approach Infinity ◽  
Interface Parameters ◽  
Film Substrate

Time-dependent deformations of bilayered elastic strips with interfacial diffusion and sliding in cylindrical bending are studied. A film–substrate system is also addressed by letting the thickness of one layer approach infinity. Our solution clearly indicates that the stresses and displacements in the strip evolve with two relaxation times when its upper surface is subjected to a sinusoidal pressure. Explicit and elementary expressions of the relaxation times are derived. The steady-state displacement jumps across the interface are found independent of the elastic property and thickness of the lower layer free of external loading. When the film is extremely thin, the relaxation times are independent of the elastic property of the substrate; when the film is extremely thick, the relaxation times are found independent of the film thickness. Detailed numerical results are presented to show the influence of the material, geometric and interface parameters on the relaxation times and on the evolving displacements and stresses in the strip or in the film–substrate system. Finally, the state-space method is proposed to determine the transient elastic field in simply supported multilayered elastic strips with interfacial diffusion and sliding under thermomechanical loads.

Transient responses of laminated anisotropic piezothermoelastic plates and cylindrical shells with interfacial diffusion and sliding in cylindrical bending

2018 ◽  
Vol 24 (4) ◽  
pp. 1065-1090 ◽  
Author(s):  
Xu Wang
Keyword(s):  
Exact Solution ◽  
State Space ◽  
Relaxation Times ◽  
The State ◽  
Laminated Plate ◽  
Interfacial Diffusion ◽  
Cylindrical Bending ◽  
Simply Supported ◽  
Elegant Method ◽  
Space Equation

With aid of the Stroh-type formalism and the state-space approach, a simple and elegant method is presented to obtain an exact solution for the time-dependent problem of a simply-supported laminated anisotropic piezothermoelastic plate in cylindrical bending with interfacial diffusion and sliding. The Stroh-type formalism is used to obtain the general solution of the thermoelectroelastic field in a certain layer. The state-space equation is then constructed for a laminated plate. The relaxation times and the transient thermoelectroelastic response of the laminated plate can be determined by solving the state-space equation via an analysis of a generalized eigenvalue problem. By using a similar method, we also derive an exact solution for a simply-supported laminated anisotropic piezothermoelastic cylindrical shell with interfacial diffusion and sliding under cylindrical bending.

PHOTORESPONSE MECHANISMS OF THIN SUPERCONDUCTING FILMS AND SUPERCONDUCTING DETECTORS

1996 ◽  
Vol 10 (06) ◽  
pp. 635-667 ◽  
Author(s):  
A. V. SERGEEV ◽  
M. YU. REIZER
Keyword(s):  
Relaxation Times ◽  
Return Time ◽  
Superconducting Film ◽  
Kinetic Inductance ◽  
Superconducting Detectors ◽  
Cooper Pairs ◽  
Superconducting Transition ◽  
Kapitza Resistance ◽  
Film Substrate ◽  
Nonequilibrium Quasiparticles

The photoresponse of ordinary and high-T c superconductors depends critically on the hierarchy of relaxation times, such as the electron–phonon and phonon–electron scattering times, the time of phonon escape from a superconducting film and also the phonon return time. For thin films of cuprates, close to the superconducting transition the following components of transient response are identified. The picosecond photoresponse is attributed to the dynamics of nonequilibrium quasiparticles and Cooper pairs. The nanosecond response is described by the thermal boundary resistance (the Kapitza resistance) between a superconducting film and a substrate. The microsecond response is associated with the phonon diffusion in the substrate. Using experimental results, we deduce the characteristic time of electron–phonon relaxation and parameters of the film-substrate interface. The kinetic inductance photoresponse of superconductors with s- and d-wave pairing far below the superconducting transition is also calculated. We study parameters (responsivity, operating speed and noise equivalent power) of a nonequilibrium detector, in which only electron states are changed under the radiation, while the film phonons stay in thermodynamic equilibrium with the substrate. Our analysis demonstrates that the nonequilibrium superconducting detectors have essential advantages compared to superconducting bolometers and other detectors.

Interfacial Diffusion in a MOCVD Grown Barium Titanate Film

1999 ◽  
Vol 591 ◽  
Author(s):  
A. Datta ◽  
Soma Chattopadhyay ◽  
A.G. Richter ◽  
J. Kmetko ◽  
C. B. Lee
Keyword(s):  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Grazing Incidence ◽  
Lattice Parameter ◽  
Composition Profile ◽  
Progressive Decrease ◽  
X Ray Diffraction ◽  
Interfacial Diffusion ◽  
X Ray ◽  
Film Substrate

ABSTRACTA combination of two nondestructive techniques, Grazing Incidence X-ray Reflectivity and High Resolution X-ray Diffraction, is used to study (at around 10Å resolution) the composition profile across a 500Å thick film of BaTiO3 grown epitaxially on (100) MgO by MOCVD. Results from both studies indicate diffusion of Mg to about 250Å into the film at film-substrate interface, consistent with the diffuse ferroelectric phase transition observed in this film. The lattice parameter a shows a progressive decrease as we move into the film from the interface, and an anomalously low value in the Mg-free portion of the film.

A nanosized rigid spherical inclusion with interfacial diffusion and sliding

2017 ◽  
Vol 23 (7) ◽  
pp. 1049-1060
Author(s):  
Xu Wang
Keyword(s):  
Steady State ◽  
Stress Field ◽  
Normal Stress ◽  
Spherical Inclusion ◽  
Surface Elasticity ◽  
Relaxation Times ◽  
Imperfect Interface ◽  
Time Dependent ◽  
Interfacial Diffusion ◽  
The Matrix

We examine the time-dependent deformations around a nanosized rigid spherical inclusion in an infinite elastic matrix under uniaxial tension at infinity. The elastic matrix is first endowed with separate Gurtin–Murdoch surface elasticity. Furthermore, interfacial diffusion and sliding both occur on the inclusion–matrix interface. Closed-form expressions of the time-dependent displacements and stresses in the matrix are derived by using Papkovich–Neuber displacement potentials. A concise and elegant expression of the steady-state normal stress on the surface of the inclusion is also obtained. It is seen that the displacements and stresses in the matrix evolve with two relaxation times which are reliant on three size-dependent parameters, one from surface elasticity and the other two from interfacial diffusion and sliding. Numerical results are presented to demonstrate the influence of surface elasticity on the relaxation times and on the stress distribution near the inclusion. It is observed that the surface elasticity can alter the nature of the steady state normal stress on the surface of the inclusion from tension to compression. When the radius of the inclusion is not greater than the ratio of residual surface tension to remote tension, the steady state normal stress on the surface of the inclusion is always compressive. The related problem of a nanosized rigid spherical inclusion with a spring-type imperfect interface is also solved. We find that it is feasible to design a neutral spherical inclusion that does not disturb a prescribed uniform uniaxial stress field or even any uniform stress field outside the inclusion through a judicious choice of the four imperfect interface parameters.

Uniqueness of Neutral Elastic Circular Nano-Inhomogeneities in Antiplane Shear and Plane Deformations

2016 ◽  
Vol 83 (10) ◽  
Author(s):  
Ming Dai ◽  
Peter Schiavone ◽  
Cun-Fa Gao
Keyword(s):  
Foreign Body ◽  
Stress Field ◽  
Antiplane Shear ◽  
Interface Effect ◽  
Interface Condition ◽  
External Loading ◽  
Surrounding Matrix ◽  
The Matrix ◽  
Interface Parameters ◽  
Plane Deformations

In elasticity theory, a neutral inhomogeneity is defined as a foreign body which can be introduced into a host solid without disturbing the stress field in the solid. The existence of circular neutral elastic nano-inhomogeneities has been established for both antiplane shear and plane deformations when the interface effect is described by constant interface parameters, and the surrounding matrix is subjected to uniform external loading. It is of interest to determine whether noncircular neutral nano-inhomogeneities can be constructed under the same conditions. In fact, we prove that only the circular elastic nano-inhomogeneity can achieve neutrality under these conditions with the radius of the inhomogeneity determined by the corresponding (constant) interface parameters and bulk elastic constants. In particular, in the case of plane deformations, the (uniform) external loading imposed on the matrix must be hydrostatic in order for the corresponding circular nano-inhomogeneity to achieve neutrality. Moreover, we find that, even when we relax the interface condition to allow for a nonuniform interface effect (described by variable interface parameters), in the case of plane deformations, only the elliptical nano-inhomogeneity can achieve neutrality.

Guided Self-Assembly via Designed Strain Field

2007 ◽  
Author(s):  
Wei Lu
Keyword(s):  
Strain Gradient ◽  
Self Assembly ◽  
Strain Field ◽  
Applied Load ◽  
Three Dimensional ◽  
Elastic Field ◽  
External Loading ◽  
Dimensional Parameter ◽  
Colony Boundary ◽  
Self Assembled

We apply an elastic field to the substrate to guide the self-assembly of domain patterns on its surface. The effect of arbitrary three dimensional external loading is found to be characterized by a single two dimensional parameter—a surface stain field of the substrate. A non-uniform strain field significantly influences the size, shape and orientation of self-assembled features, and may induce the formation of pattern colonies. It is shown that a pattern orientates normal to the strain gradient direction. An applied load anchors the position of a self-assembled pattern relative to the substrate, where a colony boundary resides on the strain gradient region. The work suggests a method of strain field design to make various monolayer patterns for nanofabrication.

Microtomy of spherical Al2O3 powders

1983 ◽  
Vol 41 ◽  
pp. 74-75
Author(s):  
E.J. Jenkins ◽  
D.S. Tucker ◽  
J.J. Hren
Keyword(s):  
Thin Film ◽  
Size Range ◽  
Particle Aggregation ◽  
Ion Milling ◽  
Thin Sections ◽  
Α Phase ◽  
Convenient Means ◽  
Van Der Waals Attraction ◽  
Negative Feature ◽  
Film Substrate

The size range of mineral and ceramic particles of one to a few microns is awkward to prepare for examination by TEM. Electrons can be transmitted through smaller particles directly and larger particles can be thinned by crushing and dispersion onto a substrate or by embedding in a film followed by ion milling. Attempts at dispersion onto a thin film substrate often result in particle aggregation by van der Waals attraction. In the present work we studied 1-10 μm diameter Al2O3 spheres which were transformed from the amprphous state to the stable α phase.After the appropriate heat treatment, the spherical powders were embedded in as high a density as practicable in a hard EPON, and then microtomed into thin sections. There are several advantages to this method. Obviously, this is a rapid and convenient means to study the microstructure of serial slices. EDS, ELS, and diffraction studies are also considerably more informative. Furthermore, confidence in sampling reliability is considerably enhanced. The major negative feature is some distortion of the microstructure inherent to the microtoming operation; however, this appears to have been surprisingly small. The details of the method and some typical results follow.

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

Structural and electronic properties of defects in semiconductors

1995 ◽  
Vol 53 ◽  
pp. 4-5
Author(s):  
J.L. Batstone
Keyword(s):  
Semiconductor Device ◽  
Chemical Vapor ◽  
Misfit Strain ◽  
Organic Chemical ◽  
Extended Defects ◽  
Transmission Electron ◽  
Semiconductor Thin Films ◽  
Wide Range ◽  
Metal Organic ◽  
Film Substrate

The development of growth techniques such as metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy during the last fifteen years has resulted in the growth of high quality epitaxial semiconductor thin films for the semiconductor device industry. The III-V and II-VI semiconductors exhibit a wide range of fundamental band gap energies, enabling the fabrication of sophisticated optoelectronic devices such as lasers and electroluminescent displays. However, the radiative efficiency of such devices is strongly affected by the presence of optically and electrically active defects within the epitaxial layer; thus an understanding of factors influencing the defect densities is required.Extended defects such as dislocations, twins, stacking faults and grain boundaries can occur during epitaxial growth to relieve the misfit strain that builds up. Such defects can nucleate either at surfaces or thin film/substrate interfaces and the growth and nucleation events can be determined by in situ transmission electron microscopy (TEM).

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