Damage and fracture evaluation of granular composite materials by digital image correlation method

This paper presents the applications of digital image correlation technique to the mesoscopic damage and fracture study of some granular based composite materials including steelfiber reinforced concrete, sandstone and crystal-polymer composite. The deformation fields of the composite materials resulted from stress localization were obtained by the correlation computation of the surface images with loading steps and thus the related damage prediction and fracture parameters were evaluated. The correlation searching could be performed either directly based on the gray levels of the digital images or from the wavelet transform (WT) coefficients of the transform spectrum. The latter was developed by the authors and showed higher resolution and sensitivity to the singularity detection. Because the displacement components came from the rough surfaces of the composite materials without any coats of gratings or fringes of optical interferometry, both surface profiles and the deformation fields of the composites were visualized which was helpful to compare each other to analyze the damage of those heterogeneous materials. The project supported by the National Natural Science Foundation of China (10125211 and 10072002), the Scientific Committee of Yunnan Province for the Program of Steel Fiber Reinforced Concrete, and the Institute of Chemical Materials, CAEP at Mianyang     

世纪之交的力学—参加第20届国际理论与应用力学大会有感

１引言 国际理论与应用力学大会 （Ｉｎｔｅｒｎａｔｉｏｎａ Ｃｏｎ－ｇｒｅｓｓ ｏｆ　Ｔｈｅｏｒｅｔｉｃａｌ　 ａｎｄ Ａｐｐｌｉｅｄ 　Ｍｅｃｈａｎｉｃｓ,简称ＩＣＴＡＭ）每四年召开一次,素有力学“奥林匹克运动会”之称．第２０届 ＩＣＴＡＭ于 ２０００年 ８月 ２７日至９月２日在美国芝加哥市举行．ＩＣＴＡＭ历来有着活跃在力学研究最前沿的众多学者出席,交流着大量成果,涉及力学理论与应用的各个方面,基本上反映出力学的整体新进展．鉴于参加本次会议的国内代表只有２０多人,应《力学进展》之约,我们共同撰写了这份报…     

An Approach for Calculating Strain Distributions in Arbitrarily Shaped Quantum Dots

We study strain distribution inside and outside an arbitrarily-shaped quantum dot (QD) buried in an infinite isotropic medium. By defining a very simple vector, we derive a compact formula for stress fields expressed by an integral over the interface between the QD and its surrounding material. Using this method, the analytical solution for a cuboidal QD is obtained, which is different from the previous result. It is shown that our solution satisfies the traction continuity condition on the interface. Based on this solution, it is found that the strain field in the cuboidal QD in the semiconductor heterostructure is sensitive to its height. In addition, the strain distribution around a hemispherical QD is also calculated and demonstrated.     

共混/填充高分子复合材料界面力学行为实验研究进展

本文首先介绍了高聚物复合材料界面微观结构的特点和界面破坏的微观形式, 在此基础上, 详细回顾了粒子填充高分子复合材料和共混高分子合金两类材料的界面力学性能实验研究的进展, 总结了研究粒子/基体界面力学性能的实验方法和用这些方法获得的实验结果。介绍的实验方法从 宏观拉伸实验到细观在位拉伸实验, 从定性的断口形貌分析到定量的界面强度和粘结能计算, 从 不同层次和角度阐述了研究界面性能各种方法的优缺点。最后, 作者根据综合分析的结果, 指出 了实验研究界面力学性能遇到的主要困难来自实验仪器的局限性和实验方法的匮乏性。为了获得 可靠的界面性能, 一方面应该设计出利于表征的界面, 另一方面需要在实验技术上有所创新。相 信该文对于深入了解和研究共混/填充高分子复合材料的界面问题, 以及其它类型材料的界面问 题具有一定的借鉴意义。     

半导体量子点结构的特性及力学研究进展

量子点结构具有独特而优异的光学和电学等性能, 是当前国际研究的热点问题之一. 量子点异质结构中的弹性场会对量子点结构的制备、加工及其光学和电学等物理性能产生重 要影响. 本文以此为背景, 从低维量子限制系统所遵循的量子力学规律及其特点、半导体量 子点的物理性能及表征、半导体量子点制备技术等方面较为全面地介绍半导体量子点结构的 研究进展, 并着重介绍在半导体量子点结构的力学研究方面以及力学性能与物理性能耦合研 究等方面的一些研究结果.     

一种孔隙介质力学模型及在水泥基材料的应用

基于细观力学和断裂力学的基本理论提出一个新的分析模型, 对孔隙介质的力学性能进行了分析. 依据孔隙介质内部孔隙的几何描述和状态参数,如孔隙率、形状、尺度及分布等,通过等效夹杂理论获得孔隙介质的等效本构方程,其最终变量为应力、应变和孔隙的形态参数. 根据断裂理论中材料承受载荷作用下破坏增长过程中的能量守恒,对孔隙介质变形过程中机械能、弹性应变能和载荷提供的势能进行分析, 根据能量守恒定律建立能量守恒方程,其最终变量也为应力、应变和孔隙的形态参数. 根据等效本构方程和能量守恒方程,获得孔隙介质承受载荷作用下的应力应变关系. 最后将该力学模型应用于水泥基材料,计算水泥基材料的力学性能并与文献中的结果进行对比分析,结果显示模型的计算结果准确有效.      

Mechanical properties of self-irradiated single-crystal copper

Molecular dynamics simulations are performed to investigate the influence of irradiation damage on the mechanical properties of copper. In the simulation, the energy of primary knocked-on atoms （PKAs） ranges from 1 to 10 keV, and the results indicate that the number of point defects （vacancies and interstitials） increases linearly with the PKA energy. We choose three kinds of simulation samples： un-irradiated and irradiated samples, and comparison samples. The un-irradiated samples are defect-free, while irradiation induces vacancies and interstitials in the irradiated samples. It is found that due to the presence of the irradiation-induced defects, the compressive Young modulus of the single-crystal Cu increases, while the tensile Young modulus decreases, and that both the tensile and compressive yield stresses experience a dramatic decrease. To analyze the effects of vacancies and interstitials independently, the mechanical properties of the comparison samples, which only contain randomly distributed vacancies, are investigated. The results indicate that the vacancies are responsible for the change of Young modulus, while the interstitials determine the yield strain.     

化学氧碘激光器的诊断

 将化学氧碘激光器(COIL)本身的诊断分述为流场特性诊断、气流混合诊断、增益介质诊断和光腔诊断, 系统讨论了各种诊断的要求, 并分别讨论了各种诊断的基本原理及方法。     

T形短肢剪力墙静力性能有限元仿真分析

利用有限元分析软件ANSYS,首先采用其中三维实体单元SOLID65建立了T形短肢剪力墙有限元分析模型,从弹性到混凝土开裂直至破坏的全过程进行了仿真试验分析。分析了影响短肢剪力墙受力的几种因素:混凝土强度等级、配筋率、轴压比、墙肢截面高厚比对短肢剪力墙承载能力、变形能力及延性的影响,剖析了短肢剪力墙破坏过程及其原因。比较真实的反映了短肢剪力墙在轴压力和逐步加载侧向力共同作用下的响应。试验结果表明:增加混凝土等级和轴压比能提高试件的开裂、屈服和极限荷载,但应综合考虑其与变形能力、延性的关系。截面配筋率具有其特殊性,配筋率在1.4%¹.6%之间时试件的承载能力、变形能力及延性较好。墙肢截面高厚比是不稳定因素但在高厚比为6.5⁷.1时,延性及变形能力较强。     

中国力学学会学术大会'2005（CCTAM'2005)会议简介

1 会议概况由中国力学学会主办,中国力学学会和北京工业大学共同承办的“中国力学学会学术大会’2005”(Chinese Conference of Theoretical and Applied Mechanics-2005,CCTAM’2005)于2005年8月26～28日在北京召开。大会主席由中国力学学会理事长崔尔杰院士担任,副主席有程耿东、贺德馨、李家春、沈为平、苏先樾、王自强、吴有生、杨卫、卢振洋、张泽。