剪胶接结构的混合模式断裂分析

给出了Ｇｏｌａｎｄ－Ｒｅｉｓｓｅｎｅｒ型剪接结构的Ｊ积分表达在被粘物体小转角和胶层很薄的假设下与路径无关。Ｊ积分代表胶层厚度与胶层内最大能量密度的乘积。对单剪接接头，本文计算了裂纹在胶层内和界面上两种情况下的局部Ｉ型和Ⅱ型应力强度因子之比，即局部载荷相角，从而给出了单剪接接头的断裂判据。     

Isothermal mass transfer in annular liquid jets with Sievert's solubility law

Summary A study of isothermal gas absorption by underpressurized, axisymmetric, thin, inviscid, incompressible, annular liquid jets which form enclosed volumes, where hazardous wastes may be burned, is presented. The study considers the nonlinear dynamical coupling between the fluid dynamics of, and the gases enclosed by, the annular liquid jet. It assumes equilibrium conditions at the interfaces, and employs Sievert's solubility law to determine the gas concentration at the gas-liquid interfaces. Both steady-state and transient conditions are considered. Under steady-state conditions, the fluid dynamics and mass transfer phenomena are uncoupled, and the rate of generation of combustion gases is equal to the mass absorption rate by the liquid. The transient behaviour of the annular jet is determined from initial conditions corresponding to steady-state operation, once there is no gas generation by the combustion of hazardous wastes. It is shown that, for most of the conditions considered in this paper, there is no leakage of gaseous combustion products through the jet's outer interface, and that the amount of gases dissolved in the liquid at the nozzle exit and the solubility ratio play a paramount role in determining the mass fluxes of hazardous combustion products at the annular jet's interfaces.The research reported in this paper was supported by Project PB91-0767 from the C.I.C.Y.T. of spain.     

两种正交异性材料界面上裂纹冲击后的动态响应

本文研究了两种不同正交异性材料界面半无限长裂纹，在冲击荷载下的动态弹塑性响应。通过积分变换，Ｗｉｅｎｅｒ－Ｈｏｐｆ方法和Ｃａｇｎｉａｒｄ－ｄｅＨｏｏｐ反演围通技术，求得一般解析解，获得了该裂纹的动应力强度因子；通过采用Ｄｕｇｄａｌｅ模型，建立了裂纹尖端塑性区延伸速度与裂纹扩展速度的关系，以及动态ＣＯＤ与裂纹扩展速度的关系。     

有限元计算中疏密网格过渡方法研究

工程计算中出于节省计算量的目的,往往需要在一个有限元模型中布置粗细不同的网格。为保证计算结果的准确性,必须保证网格突变情况下的位移协调问题。本文工作之一是在强天驰界面过渡单元的基础上,引入虚拟节点和子单元,在子单元中应用节理元思想,提出了基于最小势能原理的弹簧节理单元法。简化了积分运算,避免了精度要求极高的坐标转换,从而提高了方法的精度和实用性;二是提出了基于位移约束的主从自由度法,简便实用,只需简单的矩阵运算即可实现。两种方法均实现了不同尺寸网格间位移的协调性和刚度的匹配,从而使之满足有限元收敛准则,且生成的刚度阵具有对称性及带状性。算例证明两种方法精度良好,并可方便地应用于求解大规模工程问题。     

Dilational rheology of an air–water interface functionalized by biomolecules: the role of surface diffusion

As an attempt to develop a sensitive device for biomolecule detection, a micromechanical methodology based on the rheological change of an air–water interface is put forward (Berthier and Davoust, CEA/CNRS patent, PCT International Application WO 2003/080209 A3, 2003). Capillary waves induced from the vertical electrodynamic vibration of a brimful cylindrical tank filled with water stand as a good way to identify dilational elasticity and viscosity of an aging interface. Before, we were interested of the fact that complex wave number and the frequency of waves are obtained through an optical technique, which allows us to accurately recognize the whole interface geometry. These two parameters, a modeling based on a dispersion relation (Lucassen-Reynders and Lucassen, Adv Colloid Interface Sci, 2:347, 1969) and the surface mass transport equation, are jointly used to identify the surface diffusivity and the dilational rheology of the interface for a nonsoluble biochemical surfactant. Preliminary results obtained from a water surface functionalized by DNA, thanks to a lipidic monolayer, demonstrate the capabilities of the proposed methodology. The sensitivity of dilational rheology and the surface diffusivity on DNA adsorption on lipids is made evident.This paper was presented at the Annual Meeting of the European Society of Rheology, Grenoble, April 2005.     

Dynamic behaviour of a bubble near an elastic infinite interface

This paper presents a study to describe the behaviour of a non-equilibrium bubble in a fluid (Fluid 1) that is in contact with another fluid (Fluid 2). Fluid 2 is assumed to incorporate some elastic properties, which are modelled through a pressure term at the fluid–fluid interface. The Laplace equation is assumed to be valid in both fluids and the boundary integral method is employed to simulate the dynamics of the bubble and the fluid–fluid interface. Interesting characteristic phenomena concerning bubble oscillations and the deformation of the fluid–fluid interface are studied for a range of parameters (distance from the fluid–fluid interface, density ratios of the two fluids and elastic properties of Fluid 2). Some of the phenomena observed are jet formation in the bubble, bubble splitting, a ring bubble separating from the main bubble, mushroom-shaped bubbles and the dynamic elevation of the elastic interface. Most of these phenomena are only observed when Fluid 2 possesses some elastic properties (besides the usual formation of a high speed liquid jet). Comparisons with experimental observations confirm the validity of our simulations.     

Benchmark solution of angle-ply piezoelectric-laminated cylindrical panels in cylindrical bending with weak interfaces

The bending problem of a simply supported, angle-ply piezoelectric-laminated cylindrical panel in cylindrical bending with weak interfaces is considered. A general spring-layer model is adopted to describe the weakness of imperfect interfaces. An exact analysis is performed via the state-space approach. A new system of physical variables is introduced and a variable substitution technique is employed to derive a state equation with constant coefficients. Numerical results are given to show the effect of weak interfaces.The work was supported by the National Natural Science Foundation of China (No. 10372088) and by the Korea Institute of Science and Technology Evaluation and Planning.     

Analytical investigation of the fluid flow in the interface region between a porous medium and a clear fluid in channels partially filled with a porous medium

In this paper analytical solutions for the steady fully developed laminar fluid flow in the parallel-plate and cylindrical channels partially filled with a porous medium and partially with a clear fluid are presented. The Brinkman-extended Darcy equation is utilized to model the flow in a porous region. The solutions account for the boundary effects and for the stress jump boundary condition at the interface recently suggested by Ochoa-Tapia and Whitaker. The dependence of the velocity on the Darcy number and on the adjustable coefficient in the stress jump boundary condition is investigated. It is shown that accounting for a jump in the shear stress at the interface essentially influences velocity profiles.     

A crack perpendicular to and terminating at a bimaterial interface

Using dislocation simulation approach, the basic equation for a finite crack perpendicular to and terminating at a bimaterial interface is formulated. A novel expansion method is proposed for solving the problem. The complete solution to the problem, including the explicit formulae for theT stresses ahead of the crack tip and the stress intensity factors are presented. The stress field characteristics are analysed in detail. It is found that normal stresses {ie27-1} and {ie27-2} ahead of the crack tip, are characterised byQ fields if the crack is within a stiff material and the parameters |p _T | and |q _T | are very small, whereQ is a generalised stress intensity factor for a crack normal to and terminating at the interface. If the crack is within a weak material, the normal stresses {ie27-3} and {ie27-4} are dominated by theQ field plusT stress. This work was supported by the Swedish Research Council for Engineering Sciences.     

拉-拉循环荷载作用下的界面脱粘研究

应用弹性力学和断裂力学基本理论，基于剪滞模型，研究了纤维增强复合材料中纤维与基体界面在拉-拉循环荷载作用下的疲劳脱粘特性。建立了描述疲劳裂纹扩展的等效Paris公式，得到了界面疲劳脱粘扩展速率、脱粘应力以及脱粘界面的摩擦系数与循环加载次数的关系式。通过数值模拟计算，进一步分析了界面疲劳脱粘的力学机理。本文分析，考虑了疲劳加载引起的脱粘界面的损伤及损伤分布的不均匀性。同时还考虑了材料泊松比的影响。