Diffusion from thin layer into two semiinfinitely large bodies with different characteristics

A solution is obtained to the problem of diffusion (heat conduction) from an infinitesimally thin layer (momentary source) into two different semiinfinitely large bodies. This solution is used for calculating how much diffusion contributes to the strength of bond between a powder coating and a substrate.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 2, pp. 267–270, August, 1984.     

Exact and numerical elastodynamic solutions for spherically symmetric problems of functionally graded thick-walled spheres subjected to pressure shocks

In the present paper, analytical and numerical elastodynamic solutions are developed for spherically symmetric problems of functionally graded thick-walled spheres subjected to arbitrary dynamic and shock loads. Both transient dynamic response and elastic wave propagation characteristics are studied in the mentioned nonhomogeneous structures. Variations of the material properties across the thickness are described according to both polynomial and power law functions. The numerical consistent transfinite element formulation is presented for both functions whereas the exact solution is presented for the power law function. The functionally graded material sphere is not divided into isotropic sub-spheres. An approach associated with dividing the dynamic radial displacement expression into quasi-static and dynamic parts and expansion of the transient wave functions in terms of a series of eigenfunctions is employed to propose the exact solution. Results are obtained for various exponents of the functions of the material properties distributions, various radius ratios, and variety of dynamic and shock loads.     

Thermoelastic dynamic solution of a multilayered spherically isotropic hollow sphere for spherically symmetric problems

Summary. The thermoelastic dynamic solution of a multilayered spherically isotropic hollow sphere in the state of spherical symmetry is obtained. By the method of superposition, the displacement is divided into two parts: one is quasi-static and the other is dynamic. The quasi-static solution is first derived in an explicit form by using the transfer matrix method. Then by introducing a new dependent variable, the governing equations, boundary conditions as well as the initial conditions for the dynamic solution are rewritten, and the dynamic solution is obtained by the separation of variables method coupled with the initial parameter method as well as the orthogonal expansion technique. The present method is suitable for a multilayered spherically isotropic hollow sphere consisting of arbitrary layers and subjected to arbitrary spherically symmetric thermal loads. Numerical results are finally presented and discussed.     

Proton radiography in plasma

Generation of high intensity and well collimated multi-energetic proton beams from laser-matter interaction extends the possibility to use protons as a diagnostic tool to image imploding target in Inertial Confinement Fusion (ICF) experiments. Due to the very large mass densities reached during implosion, protons traveling through the target undergo a very large number of collisions. Therefore the analysis of experimentally obtained proton images requires care and accurate numerical simulations using both hydrodynamic and Monte Carlo codes. The impact of multiple scattering needs to be carefully considered by taking into account the exact stopping power for dense matter and for the underdense plasma corona. In our paper, density, temperature and ionization degree profiles of the imploding target are obtained by 2D hydrodynamic simulations performed using CHIC code. Proton radiography images are simulated using the Monte Carlo code (MCNPX; adapted to correctly describe multiple scattering and plasma stopping power) in order to reconstruct the complete hydrodynamic history of the imploding target. Finally we develop a simple analytical model to study the performance of proton radiography as a function of initial experimental parameters, and identify two different regimes for proton radiography in ICF.     

Analysis of thermoelastic response in a functionally graded spherically isotropic hollow sphere based on Green–Lindsay theory

This paper is concerned with the investigation of thermoelastic displacements and stresses in a functionally graded spherically isotropic hollow sphere due to prescribed temperature in the context of the linear theory of generalized thermoelasticity with two relaxation time parameters (Green and Lindsay theory). Both the surfaces of the body are free from radial stresses, and the inner surface is subjected to a time-dependent thermal shock whereas the outer one is maintained at constant temperature. The basic equations have been written in the form of a vector–matrix differential equation in the Laplace transform domain which is then solved by an eigenvalue approach. The numerical inversion of the transforms is carried out using a method of Bellman et al. The displacements and stresses are computed and presented graphically. It is found that the variation of the thermophysical properties of a material as well as the thickness of the body strongly influence the response to loading. A comparative study with the corresponding homogeneous material has also been made. The solution of the problem of a spherically isotropic infinite medium containing a spherical cavity has been derived theoretically by tending the outer radius to infinity, as a particular case.     

Measurements of the viscosity of iron and uranium under shock compression

Interest in studying the viscosity of iron and uranium is primarily associated with studying the stability of motion of envelopes made of these materials towards the center in spherically symmetric systems during the acceleration of the envelopes by the products of explosion and by shock waves. The experimental measurements of viscosity in the pressure range from 30 to 250 GPa involve the use of the method of evolution of harmonic oscillation preassigned at the front of shock wave propagating in iron and uranium. The resultant data are considered along with the estimates of the thermodynamic state of matter under shock compression.     

Ionization of a substance evaporated from a droplet in nonequilibrium plasma

An exact analytical solution is obtained for a linear stationary problem of the ionization of a spherically symmetric flux of a substance expanding in an unbounded nonequilibrium plasma. It is shown that the radial distribution of the degree of ionization in this flux is determined by a single dimensionless scaling parameter.     

EPE缓冲系统跌落冲击响应分析的变分迭代法

目的以EPE缓冲包装系统为研究对象,探讨非线性系统跌落冲击响应分析的近似解析方法。方法基于EPE系统跌落冲击试验,建立系统动力学模型,应用变分迭代法求解动力学方程,获得系统响应的一阶近似解,预测系统跌落冲击时间、最大位移及加速度等参数。结果与实测结果比较,系统跌落冲击时间、位移及加速度峰值等相对误差小于5%。结论非线性系统跌落冲击响应分析的变分迭代法具有普遍意义。     

Transient analysis of dynamic crack propagation in piezoelectric materials

Abstract

In this paper, the transient analysis of semi‐infinite propagating cracks in piezoelectric materials subjected to dynamic anti‐plane concentrated body force is investigated. The crack surface is assumed to be covered with an infinitesimally thin, perfectly conducting electrode that is grounded. In analyzing this problem, it has characteristic lengths and a direct attempt towards solving this problem by transform and Wiener‐Hopf techniques (Noble, 1958) is not applicable. In order to solve this problem, a new fundamental solution for propagating cracks in piezoelectric materials is first established and the transient response of the propagating crack is obtained by superposition of the fundamental solution in the Laplace transform domain. The fundamental solution to be used is the responses of applying exponentially distributed traction in the Laplace transform domain on the propagating crack surface. Taking into account the quasi‐static approximation, exact analytical transient solutions for the dynamic stress intensity factor and the dynamic electric displacement intensity factor are obtained by using the Cagniard‐de Hoop method (Cagnard, 1939; de Hoop, 1960) of Laplace inversion and are expressed in explicit forms. Numerical calculations of dynamic intensity factors are evaluated and the results are discussed in detail. The transient solutions for stationary cracks have been shown to approach the corresponding static values after the shear wave of the piezoelectric material has passed the crack tip.     

Two-dimensional thermal shock problem of fractional order generalized thermoelasticity

In this study, we will consider a half-space filled with an elastic material, which has constant elastic parameters. The governing equations are taken in the context of the fractional order generalized thermoelasticity theory. The medium is assumed initially quiescent. Laplace and Fourier transform techniques are used to obtain the general solution for any set of boundary conditions. The general solution is applied to a specific problem of a half-space subjected to thermal shock. The inverse Fourier transforms are obtained analytically, while the inverse Laplace transforms are computed numerically. Some comparisons have been shown in figures to estimate the effect of the fractional order on all the studied fields.     

Scattering properties of metallic carbon nanotubes in the presence of dielectric media

Scattering properties of a metallic single-walled carbon nanotube that encapsulates a nanowire is studied within the framework of classical electrodynamics. The system is assumed to be illuminated by either a transverse magnetic (TM) or a transverse electric (TE) wave. Electronic excitations on the nanotube's surface are modeled as an infinitesimally thin cylindrical layer of the π-electrons, whose dynamics are described by means of the fluid hydrodynamic theory. The problem is two-dimensional and the solution to both TM and TE uniform plane waves by the system at normal incidences is presented.     

Numerical investigations on premixed spherical flames for Lewis numbers larger than unity

We present numerical simulations of premixed spherical flames under μg conditions using the thermo-diffusive approximation. The employed numerical method is based on a finite volume discretization with explicit Runge-Kutta time integration, both of second order. A multiresolution technique is used to represent the solution on an adaptive, locally refined grid, which allows efficient and accurate computations at a reduced computational cost. We study the ignition limit, i.e. the critical radius for which the flame extinguishes, for varying Lewis numbers larger than unity. We also present fully three-dimensional simulations of initially stretched spherical flames and show their relaxation towards spherical flames, which justifies the one-dimensional spherically symmetric simulations.     

Infinitesimal rigidity of cone-like and cylinder-like frameworks

Summary Cone-like respectively cylinder-like frameworks in 3-space are constructed from plane frameworks by displacing the knots along collinear respectively parallel straight lines to at least two different positions for each knot and taking appropriate connecting bars. In [2] ist has been shown that this construction preserves shakiness. The aim of this paper is to prove that we get an infinitesimally rigid framework in space, if the plane base is assumed to be infinitesimally rigid.With 1 Figure     

Intrinsic description of 3-dimensional shock waves in nonlinear elastic fluids

The transport equations for the amplitude of 3-dimensional shock waves in nonlinear elastic fluids are examined. It is shown that, with the exception of the term which contains the mean curvature of the shock surface, the transport equations are almost identical to the transport equations for 1-dimensional nonlinear elastic solids if we replace the stress, strain and velocity in the latter by the pressure, specific volume and normal velocity, respectively. Therefore, the results obtained for 1-dimensional shock waves regarding whether the amplitudes of jump in stress, strain and velocity grow or decay simultaneously can be applied here to the jump in pressure, specific volume and normal velocity. New compatibility equations are obtained for the velocity gradients behind the shock wave. We also obtain a universal relation between the variations of amplitudes of jump in pressure, specific volume and normal velocity.     

铁电驻极体空气耦合声换能器的研制

基于多孔聚丙烯铁电驻极体薄膜系统研制了平面型和球型聚焦空气耦合超声波换能器。平面型换能器孔径为20mm,两个球型聚焦换能器的孔径和焦距分别为20mm和35mm、30mm和40mm。使用激光干涉仪测得了三个换能器作为发射器工作时的带宽和谐振频率,并且将在脉冲回波模式下测得的换能器作为接收机工作时的响应与激光干涉仪测试结果进行比较。最后选择孔径为20mm的球型聚焦换能器,在脉冲回波模式下对不同直径孔的聚乙烯阶梯楔进行扫描成像。     

The Busemann flow for a one-velocity model of a heterogeneous medium

A solution of the self-similar problem of a one-velocity multicomponent flow of a heterogeneous medium near a cone with an attached shock wave (an analog of the Busemann problem for a perfect gas) which accounts for the internal forces of interfractional interaction has been obtained. In calculating a conical shock wave, a shock adiabat of a mixture coordinated with the equation of the one-velocity model was used. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 45–51, July–August, 2007.     

埋置深度对黄麻纤维束与水泥基体粘结性能的影响

为了探究埋置深度对黄麻纤维束与水泥基体粘结性能的影响,利用C43电子式万能试验机进行了水泥基中黄麻纤维束的拔出试验,获得了拔出刚度、最大拔出力、等效粘结强度和拔出功随埋置深度的变化规律。试验在6 mm/min恒定试验速率下进行,测试了4组不同埋置深度（20 mm、40 mm、60 mm和80 mm）的试件。试验结果表明：随着埋置深度的增大,拔出刚度整体呈减小趋势但局部有波动;最大拔出力持续增大,并在埋置深度为60 mm时趋于稳定;等效粘结强度持续减小;拔出功初始增大,在埋置深度为60 mm处出现转折,而后迅速减小。为了进一步分析这种变化产生的具体作用机制,对不同埋置深度的破坏试件进行了观察,获得了试件破坏模式随埋置深度的变化规律。     

Ultrasonic solvent induced morphological change of Au colloids

Gold colloids were sonochemically synthesized in different solvents. It showed that different solvents resulted in different morphologies of Au colloids. In the mixture solution of ethanol/water, only spherical Au nanoparticles were obtained. In ethylene glycol, however, nanorod and platelet-like morphologies were formed together with spherically shaped Au nanoparticles, which resulted in optical absorption different from that of the former. Further experiment indicated that this originates mainly from different reduction rates of Au³⁺ ions in different solvents under the same sonochemical irradiation.     

Self-similar cylindrical magnetogasdynamic and ionizing shock waves

Self-similar flows behind a cylindrical blast wave in magnetogasdynamics are studied. The shock is assumed to be propagating in a medium at rest with non-uniform density permeated by an azimuthal magnetic field generated by a constant line current passing along the line source of the blast wave. The shock is a magnetogasdynamic or ionizing type according as the electrical conductivity of the gas is infinite everywhere or infinite behind the shock and zero ahead of it. For both these cases adiabatic flows as well as flows with zero temperature gradient (Isothermal) are considered. Numerical solutions for the same are obtained and a comparative study is made. It is found that, for Isothermal flows, self similar solutions do not exist, when the ambient density varies as the inverse square of the distance from the axis of symmetry along which flows the line current. A particular analytical solution has been obtained for the adiabatic flow.     

Characterization of high-frequency, single-element focused transducers with wire target and hydrophone

In this paper, a wire-target technique was used for lateral beam profile measurements for a single-element, focused transducers in the very high-frequency range (35-60 MHz). Two wire targets made from 9-cm long tungsten wires with diameters of 8 microm and 20 microm were used as the pulse-echo targets to measure the lateral beam profiles at the focal plane of two single-element, focused transducers, a spherically focused 40 MHz transducer and a lens-focused in-house lithium niobate (LiNbO3) 60 MHz transducer. For comparison, measurements on the same transducers were performed by three small-aperture hydrophones with geometrical diameters varying from 37 microm to 150 microm. Tomographic reconstruction of the acoustic field from the spherically focused transducer also was conducted. Results obtained with the wire-target technique are comparable to those obtained with small-aperture hydrophones in characterizing lateral radiation patterns of a single-element, focused transducer in the high-frequency range (35-60 MHz). However, the wire-target method may overestimate pulse length because of the additional attenuation caused by the return path. Compared to small-aperture hydrophones, the wire-target technique is simpler and more cost effective. Its major advantage, however, is in the frequency range above 100 MHz in which commercial hydrophones are not yet available.