Microcracks Propagation in One Al/SiCp under Impact Loading

Numerous microcracks propagation in one metal matrix composite, Al/SiCp under impact loading was investigated. The test data was got with a specially designed impact experimental approach. The analysis to the density, nucleating locations and distributions of the microcracks as well as microstructure effects of the original composite was received particular emphasis. The types of microcracks or debonding nucleated in the tested composite were dependent on the stress level and its duration. Distributions of the microcracks were depended on that of microstructures of the tested composite while total number of microcracks in unit area and unit duration, was controlled by the stress levels. Also, why the velocity was much lower than theoretical estimations for elastic solids and why the microcracks propagating velocities increased with the stress levels' increasing in current experiments were analysed and explained.

Characteristics of Gliding Arc Discharge Plasma

A gliding arc discharge plasma and its characteristics are described. Analysis on the production principle of the plasma is presented. Some experimental results about two novel types of the gliding arc plasma generator were obtained. These types of gliding arc plasma are potentially used in chemical industry and environment engineering.

Surface Tension and Its Temperature Coefficient of Molten Tin Determined with the Sessile Drop Method at Different Oxygen Partial Pressures

The surface tension of molten tin has been determined by the sessile drop method at The surface tension of molten tin has been determined by the sessile drop method at temperatures ranging from 523 to 1033 K and in the oxygen partial pressure (P-O2) range from 2.85 x 10(-19) to 8.56 x 10(-6) MPa, and its dependence on temperature and oxygen partial pressure has been analyzed. At P-O2 = 2.85 x 10(-19) and 1.06 x 10(-15) MPa, the surface tension decreases linearly with the increase of temperature and its temperature coefficients are -0.151 and -0.094 mNm(-1) K-1, respectively. However, at high P-O2 (3.17 x 10(-10), 8.56 x 10(-6) MPa), the surface tension increases with the temperature near the melting point (505 K) and decreases above 723 K. The surface tension decrease with increasing P-O2 is much larger near the melting point than at temperatures above 823 K. The contact angle between the molten tin and the alumina substrate is 158-173degrees, and the wettability is poor.

毛化轧辊的新方法及其应用

用脉冲激光毛化轧辊既可精确控制辊面的形貌与粗糙度又能使辊面得到强韧化。在冷轧薄钢板（带）生产中，激光毛化轧辊比目前常用的喷丸毛化轧辊有更好的使用效果和更长的使用寿命，所轧薄板的质量也更为优异。

圆柱湍流远尾迹中旋涡三维变形的数值分析

本文采用交错排列和反对称排列共同组合的离散涡模型模拟圆柱湍流远尾迹区的平均流场,应用局部化自诱导近似处理旋涡的自诱导运动,通过数值方法研究尾迹区中无穷长直线涡受到初始小扰动后的三维演化,所得结果有助于说明湍流尾迹中的相干涡结构.

热塑剪切带后期演变的准定常近似

<正> 1.基本方程式的讨论描写热塑剪切变形的近似模型方程组为其中τ和γ分别是剪应力和剪应变,θ是温度,ρ是密度,C_v是比热,γ是导热系数,t和y分别是时间和空间坐标.一般形式的本构关系为τ=τ(γ,γ,θ)(2) 如果在变形中,没有热量流出试样,则方程组(1—2)就存在一个沿y轴均匀分布,但随时间变化的解:

利用有限差分法求解扩散混合化学反应二维平行流动

利用隐式有限差分方法,对两股平行流的扩散混合、化学反应问题进行了计算。计算中,使用了层流压缩边界层方程并考虑了HF化学激光器的化学反应。计算结果表明:HF(2)振动激发态的浓度要比HF(1),HF(3)、HF(0)的浓度都高,从而获得了粒子数反转条件。另外,在计算中不需要混合长度的假设,就可以求得主流(无化学反应区)与化学反应区的两条界面曲线。当然,本文的计算方法要比直接求解二维Navier-stokes方程要简单得多。

太阳耀斑可能的储能过程

一般看法是,太阳耀斑的能量源于对流层和光球层,然后逐步堆积到外层的色球和日冕活动区中。所以,分析太阳大气中能量是如何从低层转移到上层的过程,以及分析太阳活动区中无力场能量是怎样堆积起来的机制,显然是讨论耀斑储能过程的中心问题之一。本文从冻结型无力场的基本方程组出发,不仅仅考虑旋转的环形流场,更考虑子午流场之间的相互作用,并具体推算了非定常的时间演化过程。

关于漩涡星系密度波的演化

<正> 由林家翘及其合作者在六十年代发展起来的漩涡星系密度波理论,在解释天文观测事实上取得了不少成绩。这个理论的基本观点是认为典型的漩涡星系是一种准稳态的结构,有确定的不随时间变化的图样旋转速度和幅度分布。按这样的假设提炼的数学问题是否严格有解,现在并不清楚。而由于星系的特征时间很长,也难于直接从观测上证实这种假设。从辩

Local exponential divergence plot and optimal embedding of a chaotic time-series

we propose here a local exponential divergence plot which is capable of providing a new means of characterizing chaotic time series. The suggested plot defines a time dependent exponent LAMBDA and a ''plus'' exponent LAMBDA+ which serves as a criterion for estimating simultaneously the minimal acceptable embedding dimension, the proper delay time and the largest Lyapunov exponent.

不可压缩流体三维Rayleigh-Taylor不稳定性的大涡模拟

对不可压缩流体三维Rayleigh-Taylor不稳定性问题建立被动标量输运模型，用大涡模拟方法计算了正弦初始扰动和随机初始扰动下不稳定性发展各个阶段的瞬时速度度场和标量场，以及混合过程中计算尺度和亚格子尺度上的平均湍流脉动能、平均剪切应力和被动标量通量；分析了 界面形状、被动标量浓度分布的演化规律及气泡、尖钉速度和混合层宽度随时间的变化规律，计算结果与其他数值模拟和实验结果相吻合，验证了大涡模拟方法应用于该问题的可行性。

中国力学学会学术大会’2005(CCTAM’2005)会议简介

<正>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。