平面应力的弹塑性断裂模型及其有限元分析

本文根据文献对薄钢板试样的实验分析,提出一个平面应力的弹塑性断裂模型——带状颈缩区模型.将Dugdale模型推广到弹塑性变形场情形.用弹塑性全量理论和增量理论的有限元法,分别计算了具有中心裂纹的薄宽板受均匀拉仲情形的裂纹张开位移、应力应变场.结果表明Burdekin设计曲线在一定条件下才是安全的,本文计算的裂纹张开位移与一些实验测量结果符合良好.

东方红-60推土机车架强度分析

<正> 一、问题的提出推土机车架是按装推土机各部件(发动机、减速器、后桥和驾驶座等)的基础。车架除承受这些部件的重量以及由此引起的动负荷外,还承受相当大的履带工作张力以及地面作用于车轮正向和侧向的阻力。因此在实际工作中,车架各杆件均处于拉、扭、弯、压同时作用的这一复杂而又繁重的工作载荷条件下。由于车架是推土机的基础,不管车架是变形还是损坏都会直接影响到推土机的正常使用。因此,必须保证车架有足够的强度和刚度。

关于弹性体固有频率的两个变分原理

<正> 对于几何形狀较复雜的彈性体,要嚴格地根据彈性体力学的全部方程來决定它的固有频率是有很大的困难的,因此在实际上常常采用了各式各样的近似解法,其中最有名的近似解法要算根据萊瑞原理的变分解法(称为萊瑞黎茲法)。在許多問題中,萊瑞黎兹法給出了滿意的結果。但是这个方法在实用上及理論上遺留下两个問題:第一、在許多問題中,我們往往能对应力分布的情況作适当的估計,可是这些估計在萊瑞黎兹法中不能加以充分利用;第二、在各种近似理論中,例如在梁、板、壳的近似理論中,虽然都各有自己的萊瑞原理,可是这些原理并不是彈性体力学中的萊瑞原理的直接的特殊形式。

Triple-region structure for turbulent-flow in a square duct - a finite-element approach

The Reynolds-averaged Navier-Stokes equations for describing the turbulent flow in a straight square duct are formulated with two different turbulence models. The governing equations are then expanded as a multi-deck structure in a plane perpendicular to the streamwise direction, with each deck characterized by its dominant physical forces as commonly carried out in analytical work using triple-deck expansion. The resulting equations are numerically integrated using higher polynomial (H-P) finite element technique for each cross-sectional plane to be followed by finite difference representation in the streamwise direction until a fully developed state is reached. The computed results using the two different turbulence models show fair agreement with each other, and concur with the vast body of available experimental data. There is also general agreement between our results and the recent numerical works anisotropic k-epsilon turbulence model.

Coflow jets with large velocity difference - a new aerodynamic principle of flame stabilization and combustion intensification

A new aerodynamic principle of flame stabilization and combustion intensification, the coflow jets with large velocity difference, is described. One or more small high-velocity jets of air or steam, injected off the axis and in the same direction as the low-velocity main fuel-air flow into the combustor, create a large recirculation zone of high turbulence intensity in which the combustibles and high temperature gases are effectively mixed, so that stable and intensive combustion can be maintained even for fuels with poor ignition. A pulverized coal combustor based on the principle mentioned above is shown to be characteristic of excellent combustoom and a simple structure. A number of precombustors of this type are in operation at some power stations and industrial boilers of China. Using such precombustor, successtul startups and part-load operation of the boilers have become available under conditions of unpreheated air and low-grade coal with volatiles as low as 15% and ash content as high as 30%. This principle shows good promise as an attractive new technology of combustion.

Unions, Monetary Shocks and the Labour Market Cycle

Published as an article in: Economic Modelling, 2011, vol. 28, issue 3, pages 1140-1149.

导弹水下潜射过程的流体—固体耦合仿真

导弹潜射是集高速流动、冲击、结构响应于一体的流体—固体—气体三态非线性耦合复杂过程,是决定潜射导弹发射成败的关键环节。本文应用LS-DYNA显式程序建立了三种包含水体、空气、导弹、发射井和筒盖的多物质耦合ALE网格模型,使用罚函数流体—固体耦合方法对导弹水下无攻角潜射过程进行了数值模拟,给出了弹体质心的轴向加速度、轴向流体阻力及阻力系数、空泡区压力分布。仿真结果表明,模型2的仿真过程与实际导弹潜射过程最为相符。同时总结介绍了LS-DYNA程序中流体—固体耦合计算的相关设定原则和方法。本文可为潜射导弹的水动力载荷设计和数值仿真提供有益的参考。

Endogenous Formation of Competing Partnership with Moral Hazard

Published as an article in: Games and Economic Behavior, 2003, vol. 44, issue 1, pages 183-194.

Descriptions of new genera, species and subspecies of birds from Panama, Colombia, and Ecuador

The first of January, 1912, E. A. Goldman, of the Biological Survey, Department of Agriculture, was again detailed on the Smithsonian Biological Survey of the Canal Zone. He returned to Panama in January and remained there until the last of June passing most of this period in collecting birds and mammals on the slopes of Mount Pirri on the Pacific side of eastern Panama, near the Colombian border...(Document contains 27 pages)

Whales, dolphins, and porpoises of the western North Atlantic: a guide to their identification

This is an identification guide for cetaceans (whales, dolphins, and porpoises). It was designed to assist laypersons in identifying cetaceans encountered in the western North Atlantic Ocean and was intended for use by ongoing cetacean observer programs. This publication includes sections on identifying cetaceans at sea as well as stranded animals on shore. Species accounts are divided by body size and presence or lack of a dorsal fin. Appendices cover tags used on cetacean species; how to record and report cetacean observations at see and for stranded cetaceans; and a list of contacts for reporting cetacean strandings. (Document pdf contains 183 pages - file takes considerable time to open)

Las ideas lingüísticas de Juan Mateo Zabala: El verbo regular vascongado del dialecto vizcaíno (1848)

Presentado en las II. Jornadas de Lingüística Vasco-Románica / Euskal-Erromantze Linguistika II. Jardunaldietan aurkeztua (Bilbo, 2007)

用于激波管/风洞的双爆轰驱动段

对爆轰驱动段的发展进程进行了回顾.比较了反向与前向爆轰驱动段的优缺点.提出在前向爆轰驱动段上游增加反向辅爆轰驱动段,来消除主驱动段中爆轰波后的Taylor波,改善其驱动性能.这种双爆轰驱动段只要辅与主驱动段初始压力比等于或大于临界值,主驱动段中的Taylor波将不再出现,可产生均匀的高温高压驱动气体.此外,还能产生过驱动爆轰波,进一步提高驱动能力.