Crack tip behavior and crack-propagation in ductile materials

Dilatational plastic equations, which can include the effects of ductile damage, are derived based on the equivalency in expressions for dissipated plastic work. Void damage developed internally at the large-strain stage is represented by an effective continuum being strain-softened and plastically dilated. Accumulation of this local damage leads to progressive failure in materials. With regard to this microstructural background, the constitutive parameters included for characterizing material behaviour have the sense of internal variables. They are not able to be determined explicitly by macroscopic testing but rather through computer simulation of experimental curves and data. Application of this constitutive model to mode-I cracking examples demonstrates that a huge strain concentration accompanied by a substantial drop of stress does occur near the crack tip. Eventually, crack propagation is simulated by using finite elements in computations. Two numerical examples show good accordance with experimental data. The whole procedure of study serves as a justification of the constitutive formulation proposed in the text.

Hierarchal structure of the simplified Navier-Stokes equations (SNSE) and its mechanical connotation and application

The hierarchial structure and mathematical property of the simplified Navier-Stokesequations (SNSE) are studied for viscous flow over a sphere and a jet of compressible flu-id. All kinds of the hierarchial SNSE can be divided into three types according to theirmathematical property and also into five groups according to their physical content. Amultilayers structure model for viscous shear flow with a main stream direction is pre-sented. For the example of viscous incompressible flow over a flat plate there existthree layers for both the separated flow and the attached flow; the character of thetransition from the three layers of attached flow to those of separated flow is elucidated.A concept of transition layer being situated between the viscous layer and inviscidlayer is introduced. The transition layer features the interaction between viscous flow andinviscid flow. The inner-outer-layers-matched SNSE proposed by the present author inthe past is developed into the layers matched (LsM)-SNSE.

三峡升船机系统动态响应分析

根据三峡升船机最新设计报告,采用有限元软件ANSYS构建了升船机系统有限元模型,包括承船厢、提升钢索、滑轮组、平衡重、厢内水体、驱动机构和刹车机构;通过数值模拟,对升船机系统进行了模态分析及动态响应研究,内容包括升船机系统的流固耦合模态及其在各种工况(起动、刹车、事故)下的动态响应和影响因素分析,如弹簧刚度、误载水深、阻尼、承船厢的位置等.计算结果表明:对于升船机这样一个复杂系统,该文所建立的有限元模型及数值算法是合理的,其结果可为升船机系统整体设计提供必要的参考.

直接统计模拟位置元方法中的分子表面反射确定论判据

发展的分子表面反射判据，使判断分子是否与某一表面无相撞问题得到了有效的解决。此外，还讨论了分子空间位置坐标的记录方法、分子碰撞对的极限距离、网格自适应等实际模拟技术。与圆球自由分子流准确解和过渡领域贴体网格DSMC模拟结果的比较，证明了上述判据和技术和有效性。

激光加工系统平面方程生成与误差分析补偿

研究了在三维曲面工件上进行激光加工时平面坐标及方程的生成方法、所生成的平面方程与曲面方程之间的误差及其补偿措施。平面生成方法有算术平均法、加权平均法和人工智能神经网络法，后2种方法计算精度高而被采用。

板壳断裂力学

本书阐明了板壳断裂理论的基础。论证了Reissner型板壳断裂理论的科学性、经典板壳断裂理论的缺陷及在一定范围内仍具有的实用价值；介绍了作者所创意的研究Reissner型板壳断裂纹尖端场的方法等。

目录

Adiabatic shear localization: occurrence, theories, and applications

燃烧物理学基础

Euler Solution Using Adaptive Cartesian Grid With A Gridless Boundary Treatment

A quadtree-based adaptive Cartesian grid generator and flow solver were developed. The grid adaptation based on pressure or density gradient was performed and a gridless method based on the least-square fashion was used to treat the wall surface boundary condition, which is generally difficult to be handled for the common Cartesian grid. First, to validate the technique of grid adaptation, the benchmarks over a forward-facing step and double Mach reflection were computed. Second, the flows over the NACA 0012 airfoil and a two-element airfoil were calculated to validate the developed gridless method. The computational results indicate the developed method is reasonable for complex flows.

扩展有限元方法计算多夹杂问题时圆形夹杂与四边形单元的几何关系

用扩展有限元法XFEM(Extended Finite Element Method)解决夹杂问题时,夹杂与基质的界面把单元分成若干部分.求单元刚度矩阵时,需要分别在这各个部分求积分.找到便于程序编制的描述各积分区域几何形状的方法是亟待解决的问题.本文把各积分区域的形成过程看成是圆对四边形的多次切割.考虑切剩区域与圆的关系时,把不完整的边仍看作完整的边,把切剩区域看成是四边形或是切去一两条边的四边形.采用排列组合的方法,把它们与圆的所有位置关系列了出来.

Development of high-power OPCPA laser at 1064 and 780 nm

A compact 10-TW/100-fs level ultrashort-pulse and ultra-intense laser system at 1064 nm based on optical parametric chirped pulse amplification (OPCPA) scheme is described, at which the pump and seed for the optical parametric amplification (OPA) process is optically synchronized. We investigated the output stability and the conversion efficiency of the system. Moreover, a design toward higher peak power output is given and an optically synchronized amplifier based on the concept of OPCPA at 800 nm is preliminarily explored.

Negative refraction in a honeycomb-lattice photonic crystal

In this paper we theoretically investigate a photonic crystal with dielectric rods in a honeycomb lattice. Two left-handed frequency regions are found in the second and third photonic band by using the plane wave expansion method to analyze the photonic band structure and equifrequency contours. Subwavelength imaging by the photonic crystal flat lens are systematically studied by numerical simulations using the multiple scattering method. Different from the photonic crystals with noncircular dielectric rods in air, this structure is almost isotropic at the optimal frequency for superlensing. As a comparison, flat slab focusing is also demonstrated at other frequencies in the two left-handed regions. (c) 2006 Elsevier Ltd. All rights reserved.

高激光损伤阈值溶胶-凝胶ZrO2薄膜

采用醇热法水解氧氯化锆（ZrOCl2·8H2O）制备ZrO2溶胶，提拉法涂膜。采用粘度、粒度分布、折射率、IR、DSC、AFM等测试手段对溶胶和薄膜性能进行表征。结果表明，ZrO2溶胶颗粒的平均粒径为18．9nm，薄膜经300℃热处理后折射率可高达1．95，膜层表面均匀平整，表面平均粗糙度仅为0．561nm，膜层的激光损伤阈值为14J／cm^2（1064nm，1ns）。

高稳定激光二极管抽运Nd∶YLF再生放大器

设计并实现了一种放大纳秒激光脉冲的高稳定的激光二极管(LD)抽运Nd∶YLF再生放大器。为了获得高稳定的输出,再生放大器工作在饱和状态。此时,再生放大器输出稳定性最好,而且注入激光脉冲能量波动引起的输出激光脉冲波动被抑制。由于增益饱和效应,再生放大器输出脉冲出现时域波形失真,附加后缀脉冲能够减弱时域波形失真。放大器工作波长1053nm,工作频率1Hz。输入240pJ的3ns方波激光脉冲,输出激光脉冲能量4.2mJ,总增益大于107,不稳定度小于1%(均方根),方波扭曲1.33。为3ns方波激光脉冲引入其本身幅度0.75倍的后缀脉冲,输出激光脉冲方波扭曲由1.33降至1.17。

中国古代玻璃的起源和发展

本文对中国古代玻璃的研究概况以及近半个多世纪来科技考古的结果作了简要的阐述。中国内地的古代玻璃技术产生于公元前500年春秋末战国初期。从中国出土的古代玻璃的化学成分的演变。阐明了中国古代玻璃的发展特点。并分析了中国内地的古代玻璃与西方古代玻璃的产生差异的原因。