Marangoni-Benard instability with the exchange of evaporation at liquid-vapour interface

A new two-sided model rather than the one-sided model in previous works is put forward. The linear instability analysis is performed on the Marangoni-Benard convection in the two-layer system with an evaporation interface. We define a new evaporation Biot number which is different from that in the one-sided model, and obtain the curves of critical Marangoni number versus wavenumber. The influence of evaporation velocity and Biot number on the system is discussed and a new phenomenon uninterpreted before is now explained from our numerical results.

Long-Range Stress Redistribution Resulting From Damage in Heterogeneous Media

It has been shown in CA simulations and data analysis of earthquakes that declustered or characteristic large earthquakes may occur with long-range stress redistribution. In order to understand long-range stress redistribution, we propose a linear-elastic but heterogeneous-brittle model. The stress redistribution in the heterogeneous-brittle medium implies a longer-range interaction than that in an elastic medium. Therefore, it is surmised that the longer-range stress redistribution resulting from damage in heterogeneous media may be a plausible mechanism governing main shocks.

热障涂层界面形貌尺寸与残余应力的关系

利用ANSYS有限元分析软件对热障涂层中的残余应力进行了模拟分析，得出了界面形貌尺寸与残余应力之间的关系。模拟结果表明，热障涂层中的残余应力是界面形貌尺寸的函数。这些结论为提高涂层界面结合强度的热障涂层界面造形提供了理论支持，也为热障涂层界面的优化提供了指导意见。

Dynamic stress intensity factor of a functionally graded material under antiplane shear loading

The dynamic response of a finite crack in an unbounded Functionally Graded Material (FGM) subjected to an antiplane shear loading is studied in this paper. The variation of the shear modulus of the functionally graded material is modeled by a quadratic increase along the direction perpendicular to the crack surface. The dynamic stress intensity factor is extracted from the asymptotic expansion of the stresses around the crack tip in the Laplace transform plane and obtained in the time domain by a numerical Laplace inversion technique. The influence of graded material property on the dynamic intensity factor is investigated. It is observed that the magnitude of dynamic stress intensity factor for a finite crack in such a functionally graded material is less than in the homogeneous material with a property identical to that of the FGM crack plane.

Theermal Stress and Fracture in Transparent Optical Materials due to Laser Energy-Absorption by a Defect

利用热弹性理论分析了在光学材料中由于缺陷吸收激光能量引起的温度和热应力分布,并且针对一个简单的裂纹模型分析了热应力产生的应力强度因子,给出了一些主要参数对于应力强度因子的影响的规律。

An elasto-plastic constitutive relation of whisker-reinforced metal-matrix composite

A material model for whisker-reinforced metal-matrix composites is constructed that consists of three kinds of essential elements: elastic medium, equivalent slip system, and fiber-bundle. The heterogeneity of material constituents in position is averaged, while the orientation distribution of whiskers and slip systems is considered in the structure of the material model. Crystal and interface sliding criteria are addressed. Based on the stress-strain response of the model material, an elasto-plastic constitutive relation is derived to discuss the initial and deformation induced anisotropy as well as other fundamental features. Predictions of the present theory for unidirectional-fiber-reinforced aluminum matrix composites are favorably compared with FEM results.

Microscale mechanics for metal thin film delamination along ceramic substrates

The metal thin film delamination along metal/ceramic interface in the case of large scale yielding is studied by employing the strain gradient plasticity theory and the material microscale effects are considered. Two different fracture process models are used in this study to describe the nonlinear delamination phenomena for metal thin films. A set of experiments have been done on the mechanism of copper films delaminating from silica substrates, based on which the peak interface separation stress and the micro-length scale of material, as well as the dislocation-free zone size are predicted.

A Thermodynamic Constitutive Model for Stress Induced Phase Transformation in Shape Memory Alloys

In this paper a thermodynamic constitutive model is developed for stress induced phase transformation in single crystalline and polycrystalline shape memory alloys (SMAs). Volume fractions of different martensite variants are chosen as internal variables to describe the evolution of microstructure state in the material. This model is then used in prediction the transformation behavior of a SMA (Cu-Al-Zn-Mn) under complex thermomechanical load (including complete and incomplete transformation in mechanical cycling, and proportional/non-proportional loading). (C) 2002 Elsevier Science Ltd. All rights reserved.

An overview of air-sea interface process studies

Recent progress in the study of air-sea interface processes for momentum, heat, moisture and mass transfer are reviewed in the present article. Except for turbulent structure, we have analysed the other physical mechanisms occurring in the wave boundary layer, such as the roles of the sea surface state, droplets and bubbles due to wave breaking, which at least partly account for the existing discrepancies between theory and observations. The experiments, both over the ocean and in the laboratory, are described briefly. In conclusion, a few perspective trends in this area are suggested for further investigation.

Influence of Surface Stress on Frequency of Microcantilever-Based Biosensors (vol 10, pg 307, 2004)

Microcantilever-based biosensors have been found increasing applications in physical, chemical, and biological fields in recent years. When biosensors are used in those fields, surface stress and mass variations due to bio-molecular binding can cause the microcantilever deform or the shift of frequency. These simple biosensors allow biologists to study surface biochemistry on a micro or nano scale and offer new opportunities in developing microscopic biomedical analysis with unique characteristics. To compare and illustrate the influence of the surface stress on the frequency and avoid unnecessary and complicated numerical solution of the resonance frequency, some dimensionless numbers are derived in this paper by making governing equations dimensionless. Meanwhile, in order to analyze the influence of the general surface stress on the frequency, a new model is put forward, and the frequency of the microcantilever is calculated by using the subspace iteration method and the Rayleigh method. The sensitivity of microcantilever is also discussed. (19 refs.)

Crack problems of piezoelectric materials

This paper presents an analysis of crack problems in homogeneous piezoelectrics or on the interfaces between two dissimilar piezoelectric materials based on the continuity of normal electric displacement and electric potential across the crack faces. The explicit analytic solutions are obtained for a single crack in piezoelectrics or on the interfaces of piezoelectric bimaterials. A class of boundary problems involving many cracks is also solved. For homogeneous materials it is found that the normal electric displacement D-2 induced by the crack is constant along the crack faces which depends only on the applied remote stress field. Within the crack slit, the electric fields induced by the crack are also constant and not affected by the applied electric field. For the bimaterials with real H, the normal electric displacement D-2 is constant along the crack faces and electric field E-2 has the singularity ahead of the crack tip and a jump across the interface.

Linear Stability Analysis of Convection in Two-Layer System with an Evaporating Vapor-Liquid Interface

Classical theories have successfully provided an explanation for convection in a liquid layer heated from below without evaporation. However, these theories are inadequate to account for the convective instabilities in an evaporating liquid layer, especially in the case when it is cooled from below. In the present paper, we study the onset of Marangoni convection in a liquid layer being overlain by a vapor layer.A new two-sided model is put forward instead of the one-sided model in previous studies. Marangoni-Bénard instabilities in evaporating liquid thin layers are investigated with a linear instability analysis. We define a new evaporation Biot number, which is different from that in previous studies and discuss the influences of reference evaporating velocity and evaporation Biot number on the vapor-liquid system. At the end, we explain why the instability occurs even when an evaporating liquid layer is cooled from below.

Stress intensity factors for functionally graded solid cylinders

This paper presents the mode I stress intensity factors for functionally graded solid cylinders with an embedded penny-shaped crack or an external circumferential crack. The solid cylinders are assumed under remote uniform tension. The multiple isoparametric finite element method is used. Various types of functionally graded materials and different gradient compositions for each type are investigated. The results show that the material property distribution has a quite considerable in influence on the stress intensity factors. The influence for embedded cracks is quite different from that for external cracks.

Generalized Maugis-Dugdale Model of an Elastic Cylinder in Non-Slipping Adhesive Contact with a Stretched Substrate

We have recently developed a generalized JKR model for non-slipping adhesive contact between an elastic cylinder and a stretched substrate where both tangential and normal tractions are transmitted across the contact interface. Here we extend this model to a generalized Maugis-Dugdale model by adopting a Dugdale-type adhesive interaction law to eliminate the stress singularity near the edge of the contact zone. The non-slipping Maugis-Dugdale model is expected to have a broader range of validity in comparison with the non-slipping JKR model. The solution shares a number of common features with experimentally observed behaviors of cell reorientation on a cyclically stretched substrate.