含微裂纹的95%Al_2O_3陶瓷的力学性能

本文采用三种不同加载方式(单轴拉伸,三点弯曲以及圆盘压缩)研究含微裂纹Al_2O_3的陶瓷的弹性性能及其抗拉强度.微裂纹是通过对材料瞬时突变加热和冷却(简称热冲击)形成的.试验结果表明:1)三点弯曲试验得到的力学性能参数较其它两种加载方式所得到的结果要稳定和集中.单轴拉伸试验结果分散性最大.2)热冲击温度越高,材料的等效弹性模量?和等效泊松比?以及各种加载方式下试件的抗拉强度??都有不同程度的下降.电镜观察证实了力学性能参数下降主要与材料内部微裂纹密度增加有关.3)Budiansky-O'Connell方法被用来估计不同热冲击处理后的圆盘试件在断裂过程中的微裂纹密度变化,结果表明实际材料的微裂纹密度较理想材料的微裂纹密度都有一定的偏差.

我国爆炸加工技术的发展概况

简要介绍了我国自1960年开始的爆炸加工理论、工艺及应用研究方面的进展。

强脉冲CO_2激光破坏金膜反射镜的实验研究

<正>本文对在激光研制中常用的一些不同基底的金膜反射镜,用脉宽为1微秒的10.6微米脉冲CO_2激光器,在57焦耳/厘米~2、127焦耳/厘米~2、300焦耳/厘米~2三种能量密度下进行照射,将照射结果进行了显微观察和分析并对其破坏机制进行了初步的讨论.

有限厚星系盘内域的泊松方程近似解析解

<正> 在星系密度波的渐近理论中,泊松方程的近似解析解有着十分重要的意义.对于无限薄盘,徐遐生、Bertin等以旋臂倾角参数i_0=m/kr为小参数先后求得相应泊松方程的一、二级渐近解,这些解可以很好地用于比较紧卷的螺旋结构,在平面盘密度波理论中起过重要作用;对于有限厚盘,彭秋和等人也曾得到相应泊松方程的一种解,不过此解需假定物质密度

关于“弹性圆柱薄壳的一般稳定性”问题

程世祜同志閱读了“弹性圆柱薄壳的一般稳定性”(刊登在本学报第5卷第1期)以后,曾就边界条件对失稳应力的临界值影响这一問題提出了与該文不同的意見,并写了“关于‘弹性圆柱薄壳的一般稳定性’問題”一文。 在程世祐同志的文章写就后,我們曾把它送給“弹性圆柱薄壳的一般稳定性”的原作者罗祖道、吳連元两位同志看过。“‘弹性圆柱薄壳的一般稳定性’的結束語”是这两位作者对程世祐同志提出的意見所作的解答,現在我們把这两篇有不同看法的短文一并在本期学报上发表。 組織学术討論是我們經常任务之一,希望广大的讀者能陆續对力学領域中的学术問題发表自己的意見,以使我国力学界的学术空气日益热烈。

Wave pattern characteristics of a two-phase nozzle flow by shock propagation

In this paper, the wave pattern characteristics of shock-induced two-phase nozzle Hows with the quiescent or moving dusty gas ahead of the incident-shock front has been investigated by using high-resolution numerical method. As compared with the corresponding results in single-phase nozzle flows of the pure gas, obvious differences between these two kinds of flows can be obtained.

Effect of phase-transformation on mechanical-behavior of dual-phase steel plate

The mechanical behavior of dual phase steel plates is affected by internal stresses created during martensite transformation. Analytical modelling of this effect is made by considering a unit cell made of martensite inclusion in a ferrite matrix. A large strain finite element analysis is then performed to obtain the plane stress deformation state. Displayed numerically are the development of the plastic zone and distribution of local state of stress and strain. Studied also are the shape configuration of the martensite (hard-phase) that influences the interfacial condition as related to stress transmission and damage. Internal stresses are found to enhance the global flow stress after yield initiation in the ferrite matrix. Good agreement is obtained between the analytical results and experimental observations.

Thermophoretic deposition of particles onto cold surfaces of bodies in two-dimensional and axisymmetric flows

The problem of thermophoretic deposition of small particles onto cold surfaces is studied in two-dimensional and axisymmetric flow fields. The particle concentration equation is solved numerically together with the momentum and energy equations in the laminar boundary layer with variable density effect included. It is shown explicitly to what extent the particle concentration and deposition rate at the wall are influenced by the density variation effect for external flow past bodies. The general numerical procedure is given for two-dimensional and axisymmetric cases and is illustrated with examples of thermophoretic deposition of particles in flows past a cold cylinder and a sphere.

天然气水合物分解对地层和管道稳定性影响的数值模拟

利用ABAQUS有限元程序,对海底管道及其附近地层的应力和位移场随着水合物分解范围逐渐扩大的变化情况进行了数值模拟计算。结果表明,水合物分解对管道、地层的变形和应力分布的影响显著,随着水合物分解范围的扩大,管道和地层的变形显著扩大,管道由小变形逐渐变化为整体倾倒变形,即失稳。在工程设计中,为保证地层中管道的安全,应严格控制管道附近水合物的分解范围。