材料期刊网，材料期刊，材料类期刊，材料期刊投稿

Gas tungsten arc (GTA) welding was performed both in a microgravity environment and in a terrestrial environment, and the arc shapes in both environments were compared. A microgravity condition was obtained using the free fall system at the Japan Microgravity Center. The system can maintain a 10 s microgravity of less than 10-5 g. A water-cooled Cu plate was used to simplify the arc phenomenon. The electric arc current was between 15 and 80 A, and the shielding and atmospheric gas was 99.9995% Ar and its flowing rate was 10 l/min. The polarity was a direct current electrode negative (DCEN). The arc gap was 3 mm and careful attention was also paid to the arc gap in both the terrestrial and microgravity environments being the same. As a result, it was found that no effect of gravity on the arc shape is observed under general welding conditions (over 60 A). When the electric arc current is lower than 25 A, the arc shape is determined by the initial position of the arc root and is constant with time. Accordingly, it can not be judged whether or not the arc shape is affected by gravity for this range. When the electric arc current is between 25 A and 60 A, it is estimated that the arc shape is not affected by gravity though it is occasionally affected by other minor effects.

关键词: Microgravity , null , null , null

考虑周期微结构分布特征的Mori-Tanaka方法

严鹏 , 蒋持平

复合材料学报 doi:10.3321/j.issn:1000-3851.2007.04.031

利用两点间应变Green函数张量概念所建立的应变场积分方程,推导了两相复合材料中夹杂的应变集中张量.该张量较之传统Mori-Tanaka(MT)法采用的由稀疏法导出的应变集中张量,增加了一个与夹杂体积分数和分布相关的项,并由此发展了考虑周期微结构分布特征的MT法.传统的MT法虽然能很好地预测正六角形分布圆截面纤维增强复合材料等的有效模量,但不能反映正方形分布时的四方对称性特征,本文作者所发展的方法弥补了这方面的不足,并且所预报的有效刚度和柔度仍然保持了原MT方法所具有的自洽特性.最后通过与双周期有限元计算结果的对照验证了本文方法的精度.

关键词: 双周期 , Mori-Tanaka方法 , 有效模量 , 细观力学 , 复合材料

A relation between multiple-scattering theory and micromechanical models of effective thermoelastic properties

Ceramics International

A relation between multiple-scattering theory and micromechanical models of effective elastic material properties of heterogeneous materials has been established within a unified theoretical framework, and exemplified on three important approximations. the average t-matrix (or Mori-Tanaka), symmetric self-consistency (coherent potential), and asymmetric self-consistency approximations. (C) 1996 Elsevier Science Limited and Techna S.r.l.

关键词: elastic properties;polycrystals;inclusions;matrix

N-层涂层夹杂体复合材料有效模量显示表达

戴兰宏 , 黄筑平 , 王仁

高分子材料科学与工程

利用Green函数及积分方程技术,在夹杂应变均匀的近似假定下,将Hill界面条件应用于整个二相体内,从而得到一种可以预报任意椭球夹杂体复合材料有效模量的广义自洽Mori-Tanaka方法.采用一种逐步渐进的均匀化技术将该模型推广至N层涂层夹杂问题,得到了N层涂层夹杂体复合材料的显式表达.与有的实验和理论结果比较表明,本文模型准确可靠,便于应用.同时本文还证实,采用夹杂均匀应变假定并利用Hill界面条件于两相体内可导出Mori-Tanaka平均场近似.

关键词: 涂层夹杂 , 有效模量 , 广义自洽 , 复合材料

形状记忆合金的本构模型

朱国 , 吕和祥 , 杨大智

材料研究学报 doi:10.3321/j.issn:1005-3093.2001.03.001

借助Tanaka用一维形核动力学方程导出的指数形式的相变分数,建立了一个新的形状记忆合金本构模型.提出在不同相变条件下可恢复形状记忆应变的表达式,考虑了材料在变形过程中马氏体的择优取向作用,克服了Tanaka系列模型不能描述材料处于完全马氏体状态时的力学行为的缺点.本模型比现有的形状记忆合金本构模型简单,其正确性已得到实验的检验.

关键词: 形状记忆 , 本构模型 , 伪弹性

镧与Sn-Pb合金体系中组元的相互作用关系

薛松柏 , 马鑫 , 钱乙余 ,

中国稀土学报

采用二元系Miedema生成热模型及其Tanaka过剩熵修正和三元系Chou几何模型, 分析了稀土元素La与Sn-Pb软钎料合金体系中组元元素的相互作用关系. 热力学计算表明, 在Sn-Pb合金体系中, La具有"亲Sn"倾向. 这是添加稀土元素改变Sn-Pb软钎料合金金属学性能的一个基本前提.

关键词: 稀土 , 镧 , Sn-Pb合金 , 热力学

多元合金熔体组元活度系数计算方法的改进

蒋光锐 , 刘源 , 李言祥 , 苏彦庆 , 郭景杰

金属学报

基于Miedema模型和Tanaka关系，提出了计算MIVM模型参数的新方法，开辟了计算多元合金熔体活度系数的新途径。分别计算了Ti-6Al-4V和Ti-5Al-2.5Sn在不同温度下组元活度系数的变化，计算了Zn-Sn-Pb-Cd-Bi合金活度系数与组元配比的关系，并与Wilson模型比较，计算值与实验值吻合较好。

关键词: 多元合金 , activity coefficient , Miedema model