ZHANG Cheng
,
WANG Yongzhong
,
JIANG Ming
,
ZENG Dechang
,
TANG Hong
,
LI Zhongrun
,
QIAO Guiwen
,
CHUANG Yuzhi(Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang
,
ChinaManuscript received on 20 April 1995)
金属学报(英文版)
Bi-2212 superconductive oxides with nanometer grains have been prepared by means of crystallization from amorphous materials.The structure and grain-size of samples were examined by.X-ray.diffraction,scanning electron microscopy.and high resolution electron microscopy.The temperature dependence of the resistivity.and a.c.susceptibility was measured by the standard four-probe method and the standard mutual-induction measurement,respectively.With the decrease of temperature,the resistivity of the Bi-2212 phase with grain size in nanometer was found to diminish to zero without sudden drop.No diamagnetic transition was detected from room temperature to 4.2 K.The formation of the nanocrystalline 2212 phase and the effect of grain size on the superconductivity were discussed.
关键词:
:Bi-2212
,
null
,
null
,
null
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
倪永中
,
徐鸿
材料科学与工程学报
本文提出了一种基于粒子群算法和有限元方法的弹塑性本构方程参数的确定方法,并在此基础上开发了参数自动优化系统CMPI(Constitutive Material Parameter Identification).通过使最小二乘形式的目标函数达到极小值,实现参数的动态寻优;模型参数作为粒子群优化模块的输入,采用应变(应力)控制方法,调用材料非线性有限元模块计算特定参数时的应力(应变)响应,并计算与实验数据的误差,从而实现优化过程.CMPI目前适用于A-F类模型(Chaboehe、Ohno-Wang、Jiang-Sehitoglu)的参数优化,以此为基础,不难扩展到其他材料模型.
关键词:
粒子群
,
材料非线性
,
有限元
,
Ohno-Wang 模型
张剑
,
周储伟
,
雷笑
,
叶见曙
,
卓家寿
复合材料学报
对于混杂CFRP/GFRP筋高性能混凝土(HPC)梁,研究一种新的三维非线性梁壳组合单元,对HPC梁进行了全过程分析.引入实体退化壳单元理论,利用空间梁单元模拟预应力CFRP筋,并根据CFRP筋单元节点线位移和转角位移的协调性,推导CFRP筋单元对梁壳组合单元刚度矩阵的贡献,同时对GFRP筋和HPC梁采用分层壳单元模拟.并运用Jiang屈服准则、Madrid强化准则等描述混凝土的材料非线性,提出一种新的非线性梁壳组合单元,研制相应的三维非线性计算程序.计算结果与试验数据吻合良好,说明本文构造的非线性梁壳组合单元的正确性和研制程序的可靠性,以及混凝土材料非线性描述的合理性;采用组合单元能准确模拟CFRP筋的几何构形,能综合考虑其拉压弯剪性能,利于全面地反映配筋对结构的增强作用.
关键词:
CFRP筋
,
GFRP筋
,
梁壳组合单元
,
HPC梁
,
材料非线性
