Jing HAN
,
Hongtao CHEN
,
Mingyu LI
金属学报(英文版)
A small Pb-free solder joint exhibits an extremely strong anisotropy due to the body-centered tetragonal (BCT) lattice structure of β-Sn. Grain orientations can significantly influence the failure mode of Pb-free solder joints under thermomechanical fatigue (TMF) due to the coefficient of thermal expansion (CTE) mismatch of β-Sn grains. The research work in this paper focused on the microstructure and damage evolution of Sn3.0Ag0.5Cu BGA packages as well as individual Sn3.5Ag solder joints without constraints introduced by the package structure under TMF tests. The microstructure and damage evolution in cross-sections of solder joints under thermomechanical shock tests were characterized using optical microscopy with cross-polarized light and scanning electron microscopy (SEM), and orientations of Sn grains were determined by orientation imaging microscopy (OIM). During TMF, obvious recrystallization regions were observed with different thermomechanical responses depending on Sn grain orientations. It indicates that substantial stresses can build up at grain boundaries, leading to significant grain boundary sliding. The results show that recrystallized grains prefer to nucleate along pre-existing high-angle grain boundaries and fatigue cracks tend to propagate intergranularly in recrystallized regions, leading to an accelerated damage after recrystallization.
关键词:
Pb-free solder
,
null
,
null
,
null
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null
李开明
,
李亚洲
,
冯维贵
,
林长
量子电子学报
doi:10.3969/j.issn.1007-5461.2007.05.014
采用非线性反馈控制,用附加了带参数的正弦项对Chen系统进行了有效的控制.随着参数k的逐渐增大,系统的动力学行为呈现出一系列的变化.数值研究结果表明:随控制参数的增大,驱动信号的强度渐大,混沌系统由混沌运动到周期轨道,最终到一相点.
关键词:
混沌
,
Chen系统
,
不动点
,
Lyapunov指数
,
反馈控制
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
金属学报
Volu扣ne 27SeriesB1991AUTHOR INDEX CCAO Guanghan(曹光旱)············……6一B科6CAo weijie(曹卫恋)..················……5一B32oCAO Yilin(曹益林)··················……6一B443CHANG Xin(常听)···············……1一B48CHE Guang邻n(车广灿)·············一6一B科0CHEN Erbao(陈二保)···············……6一B410CHEN Jia....
关键词:
高诚
,
胥蕊娜
,
陈黎
,
姜培学
工程热物理学报
格子Boltzmann方法(LBM)在计算复杂结构物理模型时具有独特优势并在模拟两相流动过程中能够高效清晰捕捉相界面.本文介绍了基于Shan-Chen多相模型的格子Boltzmann方法的理论成果以及基于二氧化碳封存的超临界两相流的模拟研究.结果表明,Shan-Chen模型在模拟两相流时符合Laplace定律,且两相层流时的速度分布和相渗曲线均与理论值吻合.二氧化碳封存过程中,较大的注入速率在提高二氧化碳残余俘获量的同时会降低其化学俘获量.
关键词:
二氧化碳封存
,
超临界两相流
,
Shan-Chen模型
中国腐蚀与防护学报
N。1Atmospheric Corrosivlty for Steels………………………………………………… .LIANG Caideng HO[I i。-tat（6）Caustic Stress Corrosion Cr。king of Alloy 800 Part 2.The Effect of Thiosul执e……………………………………… KONG De-sheng YANG Wu ZHAO Guo-zheng HUANG De.ltL。ZHANG Yu。。he CHEN She。g-bac（13）SERS slid E16CttOCh6iniC81 Stlldy Of Illhibit1Oli M6ch＆tllsth Of ThlollY68 Oil ITOll ID H....
关键词:
李国辉
量子电子学报
doi:10.3969/j.issn.1007-5461.2008.04.015
结合反向同步和延迟同步,提出一种新颖的反相延迟同步,基于状态观测器构造响应系统,并利用极点配置技术得到误差系统在原点处渐近稳定,实现了反相延迟同步.用Chen's混沌系统和Chua's电路为例进行数值仿真,在预先设定特征值的基础上,经极点配置可得到同步的响应系统,实验结果显示该方案简单有效.
关键词:
混沌
,
反相延迟同步
,
状态观测器
,
Chen's系统
,
Chua's电路
Journal of Nanoscience and Nanotechnology
Structural changes of Au clusters respectively containing 603 and 675 atoms with their (100) facts supported on MgO(010) surfaces at 5 K have been investigated by molecular-dynamics simulations on the atomic interchange potentials of the metal/MgO interface, which parameters are from the Ab initio energies using Chen-Mobius inversion method. As the interaction time evolves, the structural changes accompanying with atom movements are determined by decomposing peaks of pair distribution functions (PDFs) according to the pair analysis (PA) technique, and local structure patterns are identified for the supported clusters. It is shown that there exist deformation processes of the two Au clusters to adjust their atom distances owing to atom misfits among the clusters and the MgO support. Concerning these supported clusters, the obtained results reveal how the cluster size and the interaction affect the structural changes in the interaction between the supported cluster and the MgO support.
关键词:
Cluster;Molecular Dynamics;Computer Simulation;Surface;Nanostructure;molecular-dynamics;mgo(001) surface;au atoms;adsorption;dimers;mgo(100);models;dft
