CHEN Yong
,
JI Cheng
,
ZHU Miaoyong
,
WU Guorong
钢铁研究学报(英文版)
There are significant effects of process parameters on internal qualities of bloom, and these process parameters are as follows: position and reduction amount, reduction distribution, reduction rate, and so on. Developing a control model is the key to apply soft reduction technology successfully. As the research object, 360 mm×450 mm bloom caster in PISCO (Panzhihua Iron and Steel Co) has been studied, and the research method for control model of dynamic soft reduction has been proposed. On the basis of solidification and heat transfer model, the position of soft reduction and reduction distribution of each frame are determined according to the bloom temperature distribution and solid fraction in bloom center calculated. Production practice shows that the ratio of center porosity which is less than or equal to 10, increased to 9727%, ratio of central segregation which is less than or equal to 05, increased to 8091%, and ratio of central carbon segregation index which is more than or equal to 110, decreased to 4% with the applying model of dynamic soft reduction.
关键词:
bloom continuous casting;dynamic soft reduction;control model;center porosity;central segregation
H.P. Chen and Z.J. Deng (State Key Lab. for Mechanical Behavior of Materials
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China)
金属学报(英文版)
The effect of specimen thinkness on JR resistance curve has been investigated using low and middle strength steels. As the J dominance regime is reached, the initial J-integral values, J(i), are definite even if the elastic component Ji(e) and plastic component Ji(p)vary with the thinkness of specimen. The wider the specimen width, the larger the Ji(e)/Ji and the smaller the Ji(p)/Ji. The crack propagation resistance, dJR/da and dJp/da, decreases, while dJe/da increases linearly with increasing specimen thinness.Based on the above experimental results, an empirical formula dJ/da = α+β. B is given, which can be used to evaluate the safety of practical structural components.A modified J-integral is presented, upon which a new view is Put forward that the increase in crack growth resistance is induced mainly by the increase in the plastic J-integral component with the crack propagation,
关键词:
: fracture mechanics
,
null
,
null
,
null
张淑佳
,
卢炎麟
,
任立义
,
洪起超
金属学报
对20 g钢高温断裂韧性随加载速率的变化规律进行了实验研究.在400℃和500℃下,分别测量了几种加载速率下20 g钢的Ji值.实验结果表明:Ji值随应变速率的增大而有较大幅度的降低;在同一应变速率下,400℃时的Ji值小于500℃时的Ji值;400℃时裂纹扩展比500℃时更快.因此,当温度在400℃附近时更应注意避免超载.
关键词:
断裂韧性
,
null
,
null
周兰花
,
陶东平
,
曾富洪
稀有金属
doi:10.3969/j.issn.0258-7076.2011.04.011
在求解分子相互作用体积模型(MIVM)中的分子对位能参数B(ij),B(ji)时,为避免出现计算超量问题,基于遗传算法,提出了一种新算法--多个体参与交叉遗传算法,并给出了新算法的实现方案.在新算法中,采用了轮盘选种法与优秀个体保存、多个体参与交叉和多点变异等策略;选择B(ij),B(ji)个体时,按照适应度函数值愈大,个体被选中的概率愈大的原则,选择二元合金溶液中一组元活度的计算值与实验测定值之间偏差(σ)建立的适应度函数f(x)最大为优化目标.采用Matlab软件编制新算法下的B(ij),B(ji)计算程序,并分别求算了Cd-Bi,Cd-Pb,Cd-Sn,Bi-Pb,Bi-Sn,Pb-Sn等6组二元合金溶液在773 K下合金溶液的参数B(ij),B(ji)优化值.由B(ij),B(ji)计算优化值和其他一些资料数据,使用MIVM进一步预测773 K下Cd-Bi-Pb,Cd-Bi-Sn,Cd-Pb-Sn,Cd-Bi-Pb-Sn多元合金溶液中组元Cd的活度,模型预测值与实验测定值之间的相对误差低于4.6%,偏差低于0.022,两者吻合很好.结果表明,所提出的多个体参与交叉遗传算法为求解MIVM中的参数B(ij),B(ji)提供了一种有力工具,从而也能提高MIVM对多元合金溶液中组元活度的预测效果.
关键词:
MIVM模型
,
分子对位能参数Bij
,
Bji
,
遗传算法
,
活度
程开甲
,
程漱玉
稀有金属材料与工程
应用Cheng-Born能带对称破缺理论和TFDC(Thomas-Fermi-Dirac-Cheng)电子理论研究了薄膜层内电子的特性.对金属铂上的TiO2膜层来说,TFDC理论指出电子(或空穴)将由金属与膜的间界面一侧迁移到另一侧.根据Cheng-Born对称破缺理论,当能带中只有很少的电子时,则只有极少的角区中存在电子,动量空间即产生对称破缺,从而导致超导电性,并由热力学估算出薄膜超导体的转变温度.结果显示薄膜超导体的转变温度至少比块材超导体的转变温度高一个量级.作者还设计了一个研究薄膜超导电性的实验.
关键词:
超导电性
,
薄膜
,
对称破缺
,
TFDC
李翔宇
,
赵霄龙
,
郭向勇
,
曹力强
材料导报
在Cheng-Vachon模型的基础上提出了一种针对由连续相和分散相组成的两相复合材料的新导热系数模型.通过引入一个新的参数,即分散相的修正体积含量来改进Cheng-Vachon模型不适用于分散相体积含量较大的缺点.使用新的导热系数模型预测泡沫混凝土的导热系数,与实验结果的对比表明,新的模型可以准确预测泡沫混凝土的导热系数.
关键词:
泡沫混凝土
,
复合材料
,
导热系数
,
无机材料
