CuW复合材料的超声波探伤研究(一)

本文主要研究如何利用超声纵波对CuW复合材料的质量进行检测，第一部分根据CuW复合材料的缺陷特点，分步采用垂直粗探伤法和衰减精探伤法对CuW复合材料进行探伤，对比分析了探伤过程中灵敏度的确定、探头的选择以及不同牌号材料的探伤问题，从而确定了对CuW复合材料进行超声波探伤的最佳方法和参数条件。     

CuW触头着色探伤缺陷的研究

重点研究了CuW触头产品着色探伤缺陷的种类、缺陷材料机械性能、缺陷材料断口形貌宏观分析,提出了CuW触头着色探伤缺陷的判定原则和方法。材料性能试验结果表明,着色探伤缺陷产品中具有CuW疏松、CuW-Cu界面裂纹、Cu端裂纹和Cu端疏松缺陷的材料其抗拉强度、硬度低于无缺陷材料,不符合CuW触头的技术要求;具有CuW-Cu界面气孔缺陷的材料其抗拉强度与无缺陷材料相当,符合CuW触头的技术要求。通过对CuW触头着色探伤缺陷断口组织形貌宏观分析,发现着色探伤缺陷部位是CuW触头的内部缺陷组织,材料缺陷具有一定的深度,在材料受力时预先开裂,产生了应力集中,减少了材料的受力面积,使CuW触头的机械性能降低,这是导致CuW触头着色探伤缺陷机械性能低的原因。     

氮气氛烧结CuW/Cu触头材料结合强度的研究

重点研究了氮气氛烧结方法制造的CuW/Cu高压开关触头材料的结合强度,并比较了不同制造方法对CuW/Cu触头材料结合强度的影响。材料抗拉强度试验结果显示,氮气氛烧结方法制造的CuW/Cu触头材料具有最高抗拉强度,达到275MPa以上,能够满足超高电压GIS的技术要求。通过对断口的扫描电镜分析,发现氮气氛烧结的CuW/Cu触头材料结合面无氧化、无碳化、无杂质析出,材料的组织致密、孔隙少,W颗粒大小分布均匀、被Cu均匀包覆。结合面纯净和Cu端材料的高硬度可能是导致氮气氛烧结CuW/Cu触头材料结合强度高的主要原因。     

CuW/Cu整体触头气孔缺陷的消除

研制了CuW/Cu整体触头的加工工艺,同时探讨改善熔渗质量、消除熔渗气孔的方法,并对采用不同工艺制造CuW/Cu整体触头在性能和显微组织上作了对比分析。结果表明:采用氢气保护熔渗,并真空除气工艺研制的CuW/Cu整体触头密度达到理论密度的99％～100％,硬度、电阻率达到和超过国外相关标准规定的技术指标。在空气断路器、SF_6断路器上得到使用,能满足使用要求。     

铜钨(70)自力型触头的研制

本文对CuW（80）／CrCu与CuW（70）／CrCu两种自力型触头界面结合强度作了比较。研究了不同W粒粒度对CuW（70）硬度、电阻率、抗弯强度及抗电弧烧损性能的影响，用扫描电镜观察了触头烧损后的组织结构。阐述了电子束焊接方法的优点，探讨了焊后的检验手段。制造的CuW（70）／CrCu自力型触头装于ELF．SL2－1Ⅱ断路器上，通过了全部开关试验。     

小径管焊缝超声波探伤应用研究

论述小径管焊缝超声波探伤应用研究及探伤方法,分析小径管焊缝超声波探伤的特点,通过对十二种不同规格(曲率)小径管焊缝的超声波探伤试验,并经过现场实际应用,认为采用小晶片短前沿,大K值探头对小径管焊缝进行超声波探伤是切实可行的,只要探伤方法得当是能够准确检测出焊缝缺陷的,故可作为一种主要手段来检验小径管焊缝的质量。     

热等静压固相烧结CuCr合金的组织与性能研究

采用热等静压固相烧结制备了CuCr(29)Zr(1)和CuCr(28)Zr(1)TiC(1)合金,并对合金的致密度、显微组织、维氏硬度、导电率和力学性能进行了研究。结果表明:热等静压制备的CuCr触头材料组织均匀致密,近等轴状的Cr颗粒均匀分布在Cu基体中;添加TiC明显提高了合金的力学性能,而导电率变化很小。CuCr(29)Zr(1)和CuCr(28)Zr(1)TiC(1)合金的致密度分别为99.3%和99.5%,导电率为39.78%IACS和34.78%IACS,抗拉强度为357.0 MPa和374.3 MPa。材料的断裂机理为Cu基体的韧性断裂,Cr颗粒的解理断裂以及Cu与Cr的界面断裂。     

界面结构对触头可靠性影响的研究

以CuW-CuCr触头为研究对象,采用模拟仿真计算了CuW-CuCr触头不同界面结构时其界面的受力情况,同时验证了不同界面结构的触头的界面强度。结果表明,触头的CuW部分与CuCr界面的结合形式直接决定着界面处受力的大小,可以通过改变界面处的结合结构来改变界面处的受力。     

评电站管道焊缝超声波探伤的可靠性

用超声波进行管道焊缝探伤不少文献从理论和实践的角度对比作了很多论述。本文结合两个工程的实际检测情况,从缺陷检出率和探伤误判率两个方面进行分析,力图对电站管道焊缝超声波探伤的可靠性作一粗浅的评估。     

适用于电建焊接检验的超声波探伤信息处理装置

采用超声波探伤信息处理装置与普通的探伤仪结合，实现对A型探伤信息的数据采集和数据的智能化处理，有效地解决超声波检测的现场数据记录和对缺陷的精确定位问题。解决了高频信号的数据采集和有效信号的区域选择，并可按照《电力建设施工及验收技术规范》的要求打印输出检验记录。     

CuW复合材料的超声波探伤研究(二)

本文承接第一部分，主要研究了在实际超声波检测过程中如何采用对比试块通过多次反射波法和垂直扫查法对材料进行评价的方法。结合检测实际，给出了实际检测的操作方法和评价方法以及相应的参考标准波形和典型的缺陷图形。     

支柱瓷绝缘子超声波检测分析与应用

介绍超声波检测原理及爬波检测和小角度纵波检测的特点,并描述爬波检测法在现场检测中的应用,通过实例证明超声波检测法可及时发现支柱瓷绝缘子内部和表面的缺陷,保证电网安全稳定运行。     

W-Cu复合材料的应用及制造技术

简述了W-Cu复合材料在电触头、电子封装、电加工电极、国防和航空航天等领域的应用现状,介绍了熔渗法、活化液相烧结法、化学共沉淀法等W-Cu复合材料制造技术,展望了W-Cu复合材料应用及制造技术的发展方向。     

电磁声发射技术在无损检测中的应用

电磁声发射技术是通过对导电部件进行电磁加载产生洛仑兹力,进而激发声发射效应,并通过此效应来进行无损检测.它可以定位薄金属板中微小的缺陷或裂缝,而且不需要完全加载,集合了电磁无损检测技术和声发射无损检测技术的优点.建立了电磁声发射的有限元模型,分析了试件在不同加载条件下的形变,对比了几个加载因素对电磁声发射的影响,并对试件进行了温升分析.在数值分析的基础上进行了电磁声发射实验,得到了电磁声发射信号,并对缺陷进行定位.     

冷压成型方向对W-Cu电触头材料性能的影响

针对轴向、径向两种压制方向成型的W—Cu合金,采用烧结熔渗法制备W—Cu／Cu整体电触头材料,测定结合面的抗拉强度及W—Cu合金的电性能、显微组织和抗弯强度。结果表明,轴向压制产品烧结后的结合强度远大于径向压制产品烧结后的结合强度。W—Cu合金的物理性能也是轴向压制的比径向压制的好,但两种压制方法对材料的抗弯强度影响不大。     

Clog detection method in metal tubes using group delay characteristics in electromagnetic waves

In large‐scale factories or power plants metal tube clogging sometimes leads to serious accidents. However, metal tube testing for the detection of foreign objects requires a long testing time and considerable effort. Therefore, we proposed an original inspection method of a single metallic tube using electromagnetic wave reflection in the tube. However, for branched tubes, it is difficult to estimate the position of the clog by electromagnetic wave reflection. To evaluate the position of clog in the branched tubes, we proposed a new detection method using the group delay time in electromagnetic waves. The group delay time in electromagnetic waves is slightly affected by the bifurcation area. To verify the new method, the group delay time characteristics were measured in the branched tubes. The position of clog could be easily detected by the proposed method.     

Eddy current flaw testing probe with high performance in detecting flaws during in‐service inspection of tubing

Eddy current flaw testing that uses changes in the impedance of the test coil as an electromagnetic field interacts with the test material is a nondestructive testing method. It can be used to inspect test material at high speed without bringing the test coil into contact with the test material. Therefore, it is widely used for product inspection. In the inspection of heat exchanger tubing in power plants and chemical plants, eddy current flaw testing is performed by using an inner probe, because of the structural restrictions of such plants. However, high levels of wobble noise and support plate noise occur in the conventional method using a rotating pancake coil. The authors therefore propose new minimal‐noise eddy current inner probes. Two new types of probes have been developed: one for detecting axial flaws and the other for detecting circumference flaws. These probes can detect flaws with a low level of noise. The phase of the flaw signal by the new probes changes according to the flaw depth. As a result, the signal phase by the new probes can be used for evaluating the depth of surface flaws. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(2): 52–61, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20605     

Jitter at High Speed (review of "Jitter, Noise, and Signal Integrity at High-Speed" by Mike Peng Li) [Book Reviews]

This book is an outgrowth of the work its author has done in the past 15 years in the areas of jitter and jitter analysis. It covers the basics of random processes and jitter and builds on these up to systems and testing. While the book places an emphasis on basic probability theory and the mathematics of jitter, there are no problems to aid this book as a text. Despite some flaws with reference and topic coverage, the book largely succeeds at providing one source for jitter information and serves as useful reference.     

Dielectric breakdown of epoxy-based composites: relative influence of physical and chemical aging

The effect of aging on the dielectric strength of epoxy-inorganic particle composites used for insulators in the high voltage industry is reported. A differential scanning calorimetry analysis of an insulator aged twenty years in actual service conditions indicated both a chemical degradation and a structural recovery of the polymer network. This composite exhibited however a breakdown field comparable to that of a fresh sample with the same formulation. An accelerated physical aging was thus performed which lead to a large increase in the high voltage performance of the newly processes composite over time. This improvement was attributed to a densification of the thermoset resin, which impeded tree growth. It was also observed that the choice of the electrode geometry greatly alters the measurements under high electric field. In a quasi-homogeneous field configuration, the breakdown was mainly governed by the major flaws at the sample scale, namely the reinforcing particles. On the contrary, under a divergent field (with a point-plane electrode arrangement), the field was essentially localized at the point electrode tip, and the major flaws might not be reachable by the damage tree. It hence appeared that the measurements performed in a quasi-homogeneous field are not very sensitive to the variations within the polymeric matrix as are the measurements under a divergent field.