Elastic Field of a Straight Dislocation in One Dimensional Hexagonal Quasicrystals *L

目的研究准晶中的位错弹性理论．方法通过将位错分解为刃型和螺型分量,该位错引起的整个弹性场可由两个分量所引起的弹性场叠加得到．结果与结论获得了平行于准周期轴的直位错的弹性场及两个平行的直螺型位错之间的广义ＰｅａｃｈＫｏｅｈｌｅｒ力。     

一维六方准晶中直位错的弹性场

目的研究准晶中的位错弹性理论. 方法通过将位错分解为刃型和螺型分量,该位错引起的整个弹性场可由两个分量所引起的弹性场叠加得到. 结果与结论获得了平行于准周期轴的直位错的弹性场及两个平行的直螺型位错之间的广义Peach-Koehler力.     

Comments on Quasicrystals

The discoveries of so-called quasicrystals have broken through the theoretic foundation set up by the classical crystallographic group theory since 1891 and proposed new topics for study of solid structures. Electron diffraction patterns (EDP' s) and high-resolution microscopic (HREM) images have proved invaluable tools of studying the structures of crystals. The recognition and determination of EDP's and HREM images of a real-structure play a key role for understanding the structure. This paper will introduce some new developments about crystallographic group theory and new image processing methods on EDP's and HREM images. Contrary to popular beliefs, the research shows that quasicrystals can be understood (perturbed) complex periodic structures.     

平面五次对称准晶中的应力强度因子

引入一组新的应力函数来讨论平面五次对称准晶的弹性力学问题,将问题中的１８个弹性力学基本方程简化成一个高阶偏微分方程,并且应用Ｆｏｕｒｉｅｒ变换和对偶积分方程方法,求解了平面五次对称准晶结构中的Ｇｒｉｆｖｆｉｔｈ裂纹问题,得到了应力强度因子和应变能释放率,它们是研究材料变形的断裂的关键物理量。     

Stress Field of Straight Edge Dislocation in Magnetic Field

To study the changes in mechanical properties of materials within magnetic fields and the motion of dislocations, stress fields of dislocation in magnetic field need to be calculated. The straight edge dislocation is of basic importance in various defects . The stress field of straight edge dislocation in an external static magnetic field is determined by the theory of elasticity and electrodynamics according to the Volterra dislocation model for continuous media. This reduces to the known stress field when the magnet field is zero. The results can be used for further study on the strain energy of dislocations and the interactions between dislocations in magnetic fields.     

20CrMnTi钢的位错密度及晶体结构

采用X射线衍射法及新的线性分析理论,准确地测量了不同应变量时20CrMnTi钢的位错密度,分析了应变量与位错密度的关系。结果表明:位错密度随变形量的增加而提高,退火状态时位错密度较低。透射电镜试验证明了20CrMnTi退火后的组织为铁素体和珠光体,晶内位错表态为"曲折"形的位错线,变形后形成胞状结构,同时有孪晶出现。胞状结构的出现大大提高了钢的强度。     

立方准晶中螺型位错的弹性场

本文发展了立方准晶的位错弹性理论 ,通过立方准晶的反平面弹性问题的控制方程 ,得到了其含有螺型位错时的位移场与应力场的解析表达式。为研究此固体材料的塑性变形提供了重要信息。     

Yb:ZW单晶生长缺陷和光谱性能

采用丘克拉斯基法生长了３块名义掺杂浓度分别为０．０５％、０．５％、１％的ＺｎＷＯ４：Ｙｂ３＋晶体,根据Ｘ射线粉末衍射数据计算了晶胞参数,由密度实验确定了Ｙｂ３＋是以置换Ｚｎ２＋离子的方式进入晶格．观察了组分过冷和位错蚀坑,研究了不同掺杂浓度晶体的（０１０）晶面上的位错类型、连接方式,计算了位错密度．发现随着掺杂浓度的增加,位错密度也增大,必须控制合理的生长工艺条件以减少位错密度,提高晶体质量．对晶体的吸收光谱进行了测试,并对晶体的激光性能进行了讨论．     

旋光晶体中电磁声子的频率色散关系

从Born与黄昆的宏观理论出发,运用晶体光学的观点,推导出了适用于各种旋光晶体的电磁声子频率色散关系的普遍公式。     

多铁性材料中螺型位错与含弱界面圆形夹杂的相互作用

考虑无穷远反平面力载荷和平面内电磁载荷情况下,横观各向同性的压电磁介质中广义螺型位错与含非完整界面的圆形夹杂的电磁弹性耦合效应。广义螺型位错位于基体的任意一点处并且在其位错核上作用有点力、点电荷和线电流。通过运用复变函数方法,得到了电磁弹性场的解析解。借助于广义的Peach-Koehler公式,求解出了广义螺型位错上位错力的精确表达式。研究了非完整界面对夹杂区域中电磁弹性场的影响。讨论了各种参数(非完整界面,材料匹配性和位错位置)对作用在非完整界面附近广义螺型位错上位错力的影响规律。这些基本解可以作为分析压电磁介质中相应裂纹问题的格林函数。     

晶体生长机理的研究综述

控制晶体生长使材料达到最高的强度可以采取两条相反的途径:一是尽量增大位错密度,非晶态材料就可看成是位错密度极高的材料;二是尽量减少位错密度,晶须就是这种方法的一个实例.晶体生长理论研究包括晶体成核理论、输运理论、界面稳定性理论、界面结构理论和界面动力学理论的体系.揭示了晶体生长的基本过程,介绍了晶体生长的机理,概述了晶体生长理论研究的技术和控制晶体生长的途径及手段,阐述晶体生长研究的发展方向,以及晶体生长与界面相的关系.这将对晶体生长的实践起着一定的指导作用.晶体生长理论研究的发展方向是使晶体生长过程可视化,这也是晶体生长实验技术的最终目标.     

Size effect of layer thickness on stress fields due to interface core-spreading dislocation arrays in multilayers

The elastic fields due to interface dislocation arrays with spreading core in multilayers are derived analytically by means of the superposition of Green function of individual compact dislocations. The numerical results for Cu-Nb multilayers with dislocation arrays demonstrate that:(1) There exists a critical layer thickness(CLT) in describing interface shear stress. The maximum interface shear stress(MISS) increases with the layer thickness as it exceeds CLT; while the MISS decreases rapidly with the layer thickness as it is thinner than CLT.(2) Both the density and core width of interface dislocations have salient effect on the stress fields. The overall stress field is confined by high density of dislocations, and the stress singularity is released by core spreading.(3) A new dislocation prefers to glide in the middle region between the two adjacent interface dislocations by means of Peach-Kohler(P-K) force acting on the dislocation and elastic energy of dislocations. These findings would provide foundations to deepen the understanding of microscopic plastic deformation mechanisms and their related macroscopic mechanical properties of metallic anisotropic multilayers.     

Fatigue cracking characterization of high grade non-oriented electrical steels

The fatigue behavior of 30WGP1600 non-oriented electrical steel, which is generally used in the motors for electrical vehicles, was investigated. The detailed microstructure and dislocation configurations of the fatigue specimens were examined by OM, SEM, and TEM. The test results showed that fatigue cracks were commonly initiated from the surface grain boundaries, crystals plane, and inclusions. The rapid fatigue crack propagation was characterized by transgranular cleavage fracture, while most transient fracture exhibited ductile tearing characteristics. After cyclic deformation of the non-oriented electrical steels, various dislocation structures, such as short and thick lines, veins, persistent slip bands, cells, and labyrinth, were observed.     

Diffusive Wave Model and Its Applications to Biology and Physics

This study presents the diffusive wave model, relevant dispersion law and the applications to the signal transduction of live cells, phason dynamics of quasicrystals, Brownian movement, electro-magnetic field and fluid dynamics fluctuation, respectively. The common features of these diffusive waves are summarized, which present diffusion as well as wave behaviour, or exactly speaking, they present a duality of diffusion and wave or the duality of wave and diffusion. Furthermore, the general nature of the motion is discussed from the point of view of Landau elementary excitation of condensed matter, this may lead to a concept of generalized elementary excitation (or generalized quasiparticle) corresponding to the diffusive wave.     

轴对称裂纹表面受阶跃载荷的位错分布函数

通过复变函数论的方法,得到了横观各向同性体的轴对称裂纹表面受阶跃载荷作用下的位错分布函数的解析解.对具有任意的自相似指数的轴对称动态裂纹扩展问题进行求解,导出解析解的一般表达式.使得考虑的问题相应地简化,并具有一定的普遍性.     

浅谈构件可靠度基于MATLAB的蒙特卡罗法

可靠性理论已发展成为一门集综合性与边缘性为一体的学科,它涉及到基础科学、技术科学和管理科学等领域．可靠性数学是可靠性的基础理论之一,已发展成为涉及应用概率、应用数理统计和运筹学的一个边缘分支学科．从单部件的可靠度分析入手,深入研究了结构功能函数和可靠度指标的一般表达式,并给出了可靠度指标的计算公式,分析了改进的蒙特卡罗法．     

企业重建与企业组织结构形式的变革

由迈克尔·哈默和詹姆斯·钱辟提出的“企业重建”思想是近年来企业界和管理学界关注的热点。企业重建是一场新的管理革命,是对已经运行了二百多年、建立在亚当·斯密提出的分工理论基础上的企业传统运作方式的彻底改革,它要求变革传统的企业组织结构形式。矩阵组织结构是新形势下企业组织结构的一种较好形式。     

测量位错密度时位错成象的分析

本文利用晶体学知识和位错理论,对测量位错密度常用的割线交点公式2MN/(lt)进行了分析,认为这种测量方法产生误差的主要原因之一是难以选择适当的操作矢量g,以保证全部位错成象从而得到准确的N值。同时还发现了为使尽可能多的位错成象g的选择应该满足的方程组。     

Dislocation distribution model of mode Ⅲ propagation crack

Dislocation distribution functions of the edges of mode Ⅲ propagation crack subjected to three types of loads were studied by the methods of the theory of complex variable functions,by which,the problems researched were facilely transformed into Riemann-Hilbert problems and Keldysh-Sedov mixed boundary value problems. Analytical solutions of stresses,displacement and dynamic stress intensity factor were obtained by the measures of the theory of self-similar functions and corresponding differential and integral operation. In terms of the relationship between dislocation distribution functions and displacements,analytical solutions of dislocation distribution functions were obttained,and variational rules of dislocation distribution functions were depicted.     

虚影图像中去隔行算法的研究

在现代的测试系统中,大多数使用模拟的CCD隔行扫描捕获图像.由于隔行相机对运动图像捕获时,当运动目标的速度高于CCD的场积分时间时,相邻两场图像间就会发生位移,场图像合成帧图像会发生错位和虚影.本文采用三种模式方法对隔行虚影图像进行处理,一是当像素静止状态,采用前后两场内插;二是对运动状态,分别采用隔场基于块的运动估计和临场基于像素的运动补偿;三是中间状态,只能利用场内的信息来内插.最后对补偿后的图像采用中值滤波有效地抑制运动补偿的块效应.实验结论验证测试系统中隔行虚影图像得到很好的处理效果.