形状记忆合金增强复合材料连接件模型的实验研究

本文对形状记忆合金（ＳＭＡ）增强复合材料连接件模型进行了初步的实验分析和计算,结果表明：ＮｉＴｉＳＭＡ丝产生的回复应力对连接件模型孔应变有明显的影响,埋入ＮｉＴｉ丝的复合材料连接件模型的拉伸破坏载荷有所提高,本研究为改善复合材料连接的强度问题作了有益的探索。     

Determination of C54 nucleation site density in narrow stripes by sheet resistance measurements and μ-Raman spectroscopy

The kinetic of the C49–C54 phase transformation at 730°C in TiSi₂ narrow strips for width in the 0.5–1.3-μm range was investigated by resistance measurements and μ-Raman spectroscopy. With this last technique a growth rate of 0.15 μm/s and a nucleation density of about 0.035 sites/μm² were obtained. The fraction of the transformed material as measured by resistance follows the Johnson–Mehl–Avrami equation, with an exponent equal to 1 for all of the analysed linewidths. Nucleation site saturation occurs and the growth is one-dimensional along the length of the strip. The characteristic time increases as 1/W, W being the width of the strip, and, taking into account the growth rate obtained by μ-Raman spectroscopy, the nucleation density resulted 0.034 sites/μm² in excellent agreement with the μ-Raman results.     

Study on the soldering in partial melting state (1) analysis of surface tension and wettability

This paper introduces the partial melting process for solder application and characterization of its feasibility using Pb-Sn, Ag-Sn, Sn-Cu, Sn-In and Sn-Bi alloys. In order to show that the liquid phase in the semi-liquid state maintains the similar wettability as the single-phase liquid, the wetting balance tests are conducted with varying temperatures and compositions. The results are then compared with the surface tension of liquid, both measured and calculated, to examine the correlation. The results from this investigation indicate that the partial melting can yield satisfactory solder joints as long as the liquid phase acquires sufficient chemical activity. At a condition where the partial melting is effective, a direct correlation between the wettability and the surface tension is found to exist. All alloys except two, Sn-Bi and Sn-In, are found to show a reasonable wettability in semi-liquid state.     

Interfacial reactions between liquid indium and Au-deposited substrates

The morphology and growth kinetics of intermetallic compounds formed during the soldering reactions of liquid indium on Au-deposited substrates in the temperature range of 225°C and 350°C have been investigated. The results show that two types of AuIn₂ intermetallic compounds make their appearance: the continuous-wavy-crystalline type, and the floating-island type. The growth of this intermetallic compound follows the parabolic law, which indicates that the growth is diffusion-controlled. The activation energy of the reaction calculated form the Arrhenius plot of growth reaction constants is 39.42 kJ/mol. Also, the wettability of liquid indium on the surface of the gold-deposited substrate is determined from contact angle measurements. Finally, a mechanism for the interpretation of the wetting behavior of the said Au/In system is proposed, which can be ascertained by SEM observations.     

免清洗焊接技术的印刷模板设计及制造技术

印刷模板的合理设计和制造是免清洗焊接技术中的关键 ,也是SMT工艺质量的保证     

扩展电阻技术在硅,硅基材料测试中的应用

本文利用扩展电阻技术对半导体硅、硅基材料进行测试分析 ,从而用以开发新材料和评估材料的质量。     

Three-Dimensional Variational Analysis of Composite Structures Using Bernstein Polynomial Approximations. Report 1

The paper overviews the previous 3D variational analysis approaches and the numerical results obtained with the use of piecewise polynomial splines. A recently developed 3D displacement-assumed variational analysis approach is also described, where the Bernstein approximation polynomials of arbitrary degree are used as the shape functions for a 3D hexahedral discrete element of a composite body.     

Control Al/Mg intermetallic compound formation during ultrasonic-assisted soldering Mg to Al

To prevent the formation of Al/Mg intermetallic compounds (IMCs) of Al₃Mg₂ and Al₁₂Mg₁₇, dissimilar Al/Mg were ultrasonic-assisted soldered using Sn-based filler metals. A new IMC of Mg₂Sn formed in the soldered joints during this process and it was prone to crack at large thickness. The thickness of Mg₂Sn was reduced to 22 μm at 285 °C when using Sn-3Cu as the filler metal. Cracks were still observed inside the blocky Mg₂Sn. The thickness of Mg₂Sn was significantly reduced when using Sn-9Zn as the filler metal. A 17 μm Mg₂Sn layer without crack was obtained at a temperature of 200 °C, ultrasonic power of Mode I, and ultrasonic time of 2 s. The shear strengths of the joints using Sn-9Zn was much higher than those using Sn-3Cu because of the thinner Mg₂Sn layer in the former joints. Sn whiskers were prevented by using Sn-9Zn. A cavitation model during ultrasonic assisted soldering was proposed.     

Electric-pulse-induced local conducting area and joule heating effect in VO2/Al2O3 films

We investigated the effect of an electric-pulse on the insulator–metal phase transition of VO₂/Al₂O₃ films using synchrotron-based infrared microspectroscopy. By monitoring the time-resolved optical response, we could demonstrate that local conducting areas are formed under the influence of the electric-pulse, and the Joule heat generated from the local current flow drives a consecutive thermal phase transition in the adjacent sample area.     

欧洲近海结构用钢研究计划的进展

欧洲近海结构用钢研究计划在第一阶段(1975—80年)关于海洋焊接结构在疲劳载荷下工作性能的研究基础上,于1981—87年继续进行了第二阶段的研究工作。参加国家有欧洲经济共同体6国及挪威、加拿大等。本文综合报道第二阶段研究情况与主要成果,内容包括:板厚对疲劳强度的影响,焊后改进技术与腐蚀疲劳,疲劳载荷及变幅疲劳试验,疲劳分析的断裂力学方法,某些管节点的应力分析等;并对研究计划的背景及今后研究工作的方向作了介绍。