EXACT SOLUTIONS OF NEAR CRACK LINE FIELDS FOR MODE I CRACK UNDER PLANE STRESS CONDITION IN AN ELASTIC－PERFECTLY PLASTIC SOLID

ＥＸＡＣＴＳＯＬＵＴＩＯＮＳＯＦＮＥＡＲＣＲＡＣＫＬＩＮＥＦＩＥＬＤＳＦＯＲＭＯＤＥＩＣＲＡＣＫＵＮＤＥＲＰＬＡＮＥＳＴＲＥＳＳＣＯＮＤＩＴＩＯＮＩＮＡＮＥＬＡＳＴＩＣ－ＰＥＲＦＥＣＴＬＹＰＬＡＳＴＩＣＳＯＬＩＤＥＸＡＣＴＳＯＬＵＴＩＯＮＳＯＦＮＥＡ...     

A priori estimates to the maximum modulus of generalized solutions of a class of quasilinear elliptic equations with anisotropic growth conditions

ＡＰＲＩＯＲＩＥＳＴＩＭＡＴＥＳＴＯＴＨＥＭＡＸＩＭＵＭＭＯＤＵＬＵＳＯＦＧＥＮＥＲＡＬＩＺＥＤＳＯＬＵＴＩＯＮＳＯＦＡＣＬＡＳＳＯＦＱＵＡＳＩＬＩＮＥＡＲＥＬＬＩＰＴＩＣＥＱＵＡＴＩＯＮＳＷＩＴＨＡＮＩＳＯＴＲＯＰＩＣＧＲＯＷＴＨＣＯＮＤＩＴＩＯＮ...     

LARGE DEFLECTION PROBLEM OF THIN ORTHOTROPIC CIRCULAR PLATE ON ELASTIC FOUNDATION WITH VARIABLE THICKNESS UNDER UNIFORM PRESSURE

ＬＡＲＧＥＤＥＦＬＥＣＴＩＯＮＰＲＯＢＬＥＭＯＦＴＨＩＮＯＲＴＨＯＴＲＯＰＩＣＣＩＲＣＵＬＡＲＰＬＡＴＥＯＮＥＬＡＳＴＩＣＦＯＵＮＤＡＴＩＯＮＷＩＴＨＶＡＲＩＡＢＬＥＴＨＩＣＫＮＥＳＳＵＮＤＥＲＵＮＩＦＯＲＭＰＲＥＳＳＵＲＥ（王嘉新）（刘杰）ＬＡＲＧ...     

Application of the probabilistic fracture mechanics method of predicting the fatigue life of tubular joints

ＡＰＰＬＩＣＡＴＩＯＮＯＦＴＨＥＰＲＯＢＡＢＩＬＩＳＴＩＣＦＲＡＣＴＵＲＥＭＥＣＨＡＮＩＣＳＭＥＴＨＯＤＯＦＰＲＥＤＩＣＴＩＮＧＴＨＥＦＡＴＩＧＵＥＬＩＦＥＯＦＴＵＢＵＬＡＲＪＯＩＮＴＳＮｉｅＧｕｏ－ｈｕａ（聂国华）ＷｅｎｇＺｈｉ－ｙｕａｎ（翁智远）...     

ANALYTICAL SOLUTION OF RADIATED SOUND PRESSURE OF RING－STIFFENED CYLINDRICAL SHELLS IN FLUID MEDIUM

ＡＮＡＬＹＴＩＣＡＬＳＯＬＵＴＩＯＮＯＦＲＡＤＩＡＴＥＤＳＯＵＮＤＰＲＥＳＳＵＲＥＯＦＲＩＮＧ－ＳＴＩＦＦＥＮＥＤＣＹＬＩＮＤＲＩＣＡＬＳＨＥＬＬＳＩＮＦＬＵＩＤＭＥＤＩＵＭＸｉｅＧｕａｎｍｏ（谢官员模）ＬｕｏＤｏｎｇｐｉｎｇ（骆东平）（Ｒｅｃｅｉｖ...     

QUASI－FLOW CORNER THEORY ON LARGE PLASTIC DEFORMATION OF DUCTILE METALS AND ITS APPLICATIONS

ＱＵＡＳＩ－ＦＬＯＷＣＯＲＮＥＲＴＨＥＯＲＹＯＮＬＡＲＧＥＰＬＡＳＴＩＣＤＥＦＯＲＭＡＴＩＯＮＯＦＤＵＣＴＩＬＥＭＥＴＡＬＳＡＮＤＩＴＳＡＰＰＬＩＣＡＴＩＯＮＳＨｕＰｉｎｇ（胡平）ＬｉｕＹｕｑｉ（柳玉启）ＧｕｏＷｅｉ（郭威）ＴａｉＦｅｎｇ（台风）（Ｒ...     

RELATIVISTIC VARIATION PRINCIPLES AND EQUATION OF MOTION FOR VARIABLE MASS CONTROLLABLE MECHANICAL SYSTEM

ＲＥＬＡＴＩＶＩＳＴＩＣＶＡＲＩＡＴＩＯＮＰＲＩＮＣＩＰＬＥＳＡＮＤＥＱＵＡＴＩＯＮＯＦＭＯＴＩＯＮＦＯＲＶＡＲＩＡＢＬＥＭＡＳＳＣＯＮＴＲＯＬＬＡＢＬＥＭＥＣＨＡＮＩＣＡＬＳＹＳＴＥＭ￥(罗绍凯)ＬｕｏＳｈａｏｋａｉ（ＳｈａｎｇｑｉｕＴｅａｃｈｅｒｓ...     

MOTION EQUATIONS OF MULTILAYERED ELASTIC ELECTROCONDUCTIVE PLATES IN A MAGNETIC FIELD

ＭＯＴＩＯＮＥＱＵＡＴＩＯＮＳＯＦＭＵＬＴＩＬＡＹＥＲＥＤＥＬＡＳＴＩＣＥＬＥＣＴＲＯＣＯＮＤＵＣＴＩＶＥＰＬＡＴＥＳＩＮＡＭＡＧＮＥＴＩＣＦＩＥＬＤＧｏｕＸｉｎｇ－ｈｕａ（苟兴华）（ＳｉｃｈｕａｎＵｎｉｖｅｒｓｉｔｙ,Ｃｈｅｎｇｄｕ）ＺｈａｎｇＦａ...     

A COMPARATIVE STUDY OF THE OPENING AND CLOSING PROCESS OF TWO TYPES OF MECHANICAL HEART VALVES USING ALE FINITE ELEMENT METHOD

ＡＣＯＭＰＡＲＡＴＩＶＥＳＴＵＤＹＯＦＴＨＥＯＰＥＮＩＮＧＡＮＤＣＬＯＳＩＮＧＰＲＯＣＥＳＳＯＦＴＷＯＴＹＰＥＳＯＦＭＥＣＨＡＮＩＣＡＬＨＥＡＲＴＶＡＬＶＥＳＵＳＩＮＧＡＬＥＦＩＮＩＴＥＥＬＥＭＥＮＴＭＥＴＨＯＤＡＣＯＭＰＡＲＡＴＩＶＥＳＴＵＤＹＯＦ...     

THE ANALYTICAL STUDY ON THE LASER INDUCED REVERSE－PLUGGING EFFECT BY USING THE CLASSICAL ELASTIC PLATE THEORY（II）──REVERSE－BULGE MOTION

ＴＨＥＡＮＡＬＹＴＩＣＡＬＳＴＵＤＹＯＮＴＨＥＬＡＳＥＲＩＮＤＵＣＥＤＲＥＶＥＲＳＥ－ＰＬＵＧＧＩＮＧＥＦＦＥＣＴＢＹＵＳＩＮＧＴＨＥＣＬＡＳＳＩＣＡＬＥＬＡＳＴＩＣＰＬＡＴＥＴＨＥＯＲＹ（ＩＩ）──ＲＥＶＥＲＳＥ－ＢＵＬＧＥＭＯＴＩＯＮ￥(周益春，...     

大量椭球颗粒随机分布三维区域的模拟及其四面体网格快速生成算法

针对颗粒为椭球形状并且随机分布的多相复合材料给出了三维情形下的计算机模拟方法,并对此复杂区域提供了一种四面体网格快速生成算法。此方法的基本思想:首先是根据材料的要求,给出随机颗粒材料的计算机模拟,然后对模拟后的颗粒边界初始化,得到一些初始剖分点,并给出剖分区域的初始网格(正四面体),接着把颗粒的初始边界点投入到剖分区域中,替换区域中靠此点近的点,并且采用加点寻找边界的方法和修正初始点方法来解决四面体穿刺边界问题,从而得到整个区域的四面体网格。最后用实例说明了算法的有效性。     

Mechanical study of the effect of fractional-wettability on multiphase fluid flow

Fractional wettability has been widely recognized in most of the oil reservoirs and it is a crucial factor that controls the fluid flow behavior in porous medium. The overall effect of the proportion of oil-wet grains on the fluid flow properties has been well discussed. However, recent studies found that the random distribution and coordination of oil-wet and water-wet grains could make multi-phase flow behaviors extremely complicated in such media. The multiphase flow mechanisms in fractional wettability media remains unclear. In this study, oil imbibition experiments were systematically conducted using glass cylinders packed with fractional-wet glass beads. To study the effect of fractional wettability on multiple-phase flow properties, samples with different oil-wet grain proportions were prepared, and fifteen repeated experiments were conducted for each oil-wet proportion. The experimental results showed that oil imbibition was largely dependent on but not strictly a function of the proportion of oil-wet grains in the medium. The imbibition behaviors of samples with the same fractional proportion could vary significantly, as some samples exhibited complete oil migration, while others did not. This probabilistic phenomenon is likely due to the random distribution of oil-wet and water-wet grains. A pore throat may behave as oil-wet or water-wet depending on the relative proportion of oil-wet grains the pore throat contains. When the grains that comprise the pore throat are dominated by oil-wet grains, the throat behaves as oil-wet, and vice versa. Only when these oil-wet pore throats are connected to form a complete oil-wet pathway throughout the medium can the oil continuously imbibe into the medium. Therefore, the extent of oil imbibition depends on the completeness of the oil-wet pathway, which is controlled by the proportion of oil-wet grains in the medium. The higher the proportion of oil-wet grains in the medium, the larger the number of oil-wet pore throats that can form; thus, the higher the possibility that those oil-wet pore throats can connect to form continuous oil-wet pathways.     

Effect of Reactive Surface Areas Associated with Different Particle Shapes on Chemical-Dissolution Front Instability in Fluid-Saturated Porous Rocks

In this article, the effect of reactive surface areas associated with different particle shapes on the reactive infiltration instability in a fluid-saturated porous medium is investigated through analytically deriving the dimensionless pore-fluid pressure-gradient of a coupled system between porosity, pore-fluid flow and reactive chemical-species transport within two idealized porous media consisting of spherical and cubic grains respectively. Compared with the critical dimensionless pore-fluid pressure-gradient of the coupled system, the derived dimensionless pore-fluid pressure-gradient can be used to assess the instability of a chemical dissolution front within the fluid-saturated porous medium. The related theoretical analysis has demonstrated that (1) since the shape coefficient of spherical grains is greater than that of cubic grains, the chemical system consisting of spherical grains is more unstable than that consisting of cubic grains, and (2) the instability likelihood of a natural porous medium, which is comprised of irregular grains, is smaller than that of an idealized porous medium, which is comprised of regular spherical grains. To simulate the complicated morphological evolution of a chemical dissolution front in the case of the chemical dissolution system becoming supercritical, a numerical procedure is proposed for solving this kind of problem. The related numerical results have demonstrated that the reactive surface area associated with different particle shapes can have a significant influence on the morphological evolution of an unstable chemical-dissolution front within fluid-saturated porous rocks.     

Elastostatic computations on aggregates of grains with sharp interfaces,corners, and triple-junctions

We present a fast algorithm for the calculation of elastostatic fields in two-dimensional assemblies of elastic grains, separated by sharp grain boundaries. The algorithm uses an integral equation approach, combined with the fast multipole method and recursive compression to resolve stress concentrations also very close to grain boundary junctions. Singular basis functions on analytic form are not required. Accurate results can be obtained at a cost roughly proportional to the number of grains in the assembly. Large-scale problems, with thousands of grains, are solved using modest computational resources.     

A procedure for estimating Young’s modulus of textured polycrystalline materials

In this study, a procedure for estimating Young’s modulus of textured and non-textured polycrystalline materials was examined based on finite element analyses, which were performed using three-dimensional polycrystalline finite element models of a random structure, generated using the Voronoi tessellation. Firstly, the local stress/strain distribution and its influence on macroscopic elastic properties were evaluated. Then, the statistical relationship between Young’s modulus obtained from the finite element analyses and averaged Young’s modulus of all grains evaluated based on Voigt’s or Reuss’ model was investigated. It was revealed that the local stress/strain in the polycrystalline body is affected by crystal orientation and deformation constraint caused by adjacent grains, whereas only the crystal orientation affects Young’s modulus of the polycrystalline body when the number of grains is large enough. It was also shown that Young’s modulus correlates well with the averaged Young’s modulus of all grains, in which the size of grains is considered in the averaging. Finally, a procedure for estimating Young’s modulus of textured and non-textured materials was proposed. Young’s modulus of various materials can be estimated from the elastic constants of single crystal and the distribution of crystal orientation and size of grains, which can be obtained by using electron backscatter diffraction (EBSD).     

Three-dimensional characterization of strain localization bands in high-resolution elastoplastic polycrystals

In crystalline materials, the experimental observation of the localization of plastic strains in particular directions is generally restricted to the surface of a sample containing some hundreds of grains, because of the difficulties underlying microstructural analysis. In these conditions, the determination of the morphological characteristics of localization can be limited by the poor statistical representativity of the domain of observation. The purpose of this work is to extend the analysis of localization – localization bands or else – to the 3D elastoplastic strain fields of a high-resolution representative volume element of a polycrystal.     

Study on Deformation of Polycrystalline Aluminum Alloy Using Moiré Interferometry

Polycrystalline aluminum alloy is manufactured by annealing, compared to the width of the specimen, the size of the grains can not be omitted, which makes the specimen anisotropic. Under uniaxial tension, the deformation field is inhomogeneous. In this study, moiré interferometry is successfully applied to measure the deformation of the polycrystalline specimen. The experimental results presented the stress versus strain responses of the marked grains in different orientations and different shapes. By using fringe centering method, the strain distributions under certain load in the centers and on the boundaries of the grains are analyzed.     

A multivariant micromechanical model for SMAs Part 2. Polycrystal model

An averaging scheme is developed to simulate the behavior of a polycrystalline shape memory alloy (SMA) specimen using the Multivariant Micromechanics approach. An untextured polycrystalline specimen is assumed to be formed by a number of randomly oriented single crystal grains. The previously developed Multivariant technique is used to model the response of each single crystal grain subjected to its stress field seen in the polycrystalline sample. Using spherical grains, the Eshelby–Kröner approach is used to formulate the interaction between grains and to determine the stress state in each individual grain. This model successfully captures the basic features of SMA polycrystalline response to loading and temperature. In addition, comparison is made to recent experimental data with fully triaxial load states. Reasonable qualitative agreement is obtained and some issues related to crystallography of the material model are addressed.     

考虑尺寸效应的多晶金属循环塑性分析

本文采用多晶塑性分析方法,设材料点包含一定数量的各向异性单晶晶粒并考虑晶粒尺寸的影响,计算材料点的应力和应变时利用了Taylor假设。模型引入考虑尺寸效应的晶体滑移硬化函数,同时针对晶体滑移引入背应力及其方向性硬化的描述,以反映不同晶粒尺寸材料在循环加载条件下的力学行为。利用该模型,本文第一作者采用显式格式编制了与ABAQUS商用有限元软件接口的用户材料子程序（VUMAT）,实例计算证实该模型可以反映和描述多晶金属材料在材料反复加载条件下的循环塑性行为与尺寸效应。     

Towards a constitutive law for the unsteady contact stress in granular media

In order to build a unified modelling for granular media by means of Eulerian averaged equations, it is necessary to study two contributions in the effective Cauchy stress tensor: the first one concerns solid and fluid matter, including contact and collisions between grains; the second one focuses on the random movements of grains and fluid, similar to Reynolds stress for turbulent flows. It is shown that the point of view of piecewise continuous media already used for two phase flows allows one to derive a constitutive equation for the first contribution, under the form of a partial differential equation. Similarly as for the Reynolds stress in turbulent flows, this equation cannot be written only in terms of averaged quantities without adequate approximations. The structure of the closed equation is discussed with respect to irreversible thermodynamics, and in connection with some already existing models. It is emphasised that numerical simulations by the discrete elements method can be used in order to validate these approximations, through numerical experiments statistically considered. Finally an extension of this approach to the second contribution of the effective Cauchy stress tensor is briefly discussed, showing how the modelling of both contributions have to be coupled.