Combination of Metal Shielding and Distance Estimation for Electromagnetic Compatibility Guarantee

In this paper, a solution for electromagnetic compatibility guarantee based on the combination of metal shielding and circuit components distance estimation methods is presented. The electromagnetic noises generated from a working radio-electronic unit can expand into the space and act on other around radio-electronic units. An EMC guaranteed radio-electronic unit by the suitable technique method will not cause the electromagnetic noise to others. In opposition, it will not be under electromagnetic action from another one. Due to the power of electromagnetic noise, the metal shielding, distance estimation or other technique methods should be used to guarantee EMC. Every method has own advantage as so as weakness for detail radio-electronic unit, so it is necessary to choose a suitable method to guarantee EMC for them, the combination of metal shielding and distance estimation is a choice, for example. The proposed solution has been evaluated by using CST (Computer Simulation Technology) software and EMxpertEHX analyzer in oscillator circuit context. The simulated results on CST show that the proposed solution decreases the electromagnetic radiation about of 39.1 dB at frequency 500 MHz in comparison to results when nothing electromagnetic compatibility methods are not used. The experimental results on the oscillator circuit are presented. The electromagnetic radiation reduction of the oscillator circuit is about of (25 - 30) dB. In comparison to individual metal shielding and distance estimation methods, the effectiveness of the proposed solution for electromagnetic compatibility guarantee is significantly increased.

Tensile and Impact Properties of Shielded Metal Arc Welded AISI 409M Ferritic Stainless Steel Joints

The present study is concerned with the effect of filler metals such as austenitic stainless steel, ferritic stainless steel and duplex stainless steel on tensile and impact properties of the ferritic stainless steel conforming to AISI 409M grade. Rolled plates of 4 mm thickness were used as the base material for preparing single pass butt welded joints. Tensile and impact properties, microhardness, microstructure and fracture surface morphology of the joints fabricated by austenitic stainless steel, ferritic stainless steel and duplex stainless steel filler metals were evaluated and the results were reported. From this investigation, it is found that the joints fabricated by duplex stainless steel filler metal showed higher tensile strength and hardness compared to the joints fabricated by austenitic and ferritic stainless steel filler metals. Joints fabricated by austenitic stainless steel filler metal exhibited higher ductility and impact toughness compared with the joints fabricated by ferritic stainless steel and duplex stainless steel filler metals.

A transparent electromagnetic-shielding film based on one-dimensional metal–dielectric periodic structures

In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding medium, which not only transmits visible light but also inhibits the transmission of microwaves, despite the fact that the total thickness of the Ag film is much larger than the skin depth in the visible range and less than that in the microwave region. Theoretical results suggest that a high dielectric/metal thickness ratio can enhance the broadband and improve the transmittance in the optical range. Accordingly, the central wavelength was found to be red-shifted with increasing dielectric/metal thickness ratio. A physical mechanism behind the controlling transmission of visible light is also proposed. Meanwhile, the electromagnetic shielding effectiveness of the prepared structures was found to exceed 40 dB in the range from 0.1 GHz to 18 GHz, even reaching up to 70 dB at 0.1 GHz, which is far higher than that of a single ITO film of the same thickness.

Radiation Shielding Performance of Aggregates Made by Sludge with High Content of Heavy Metal

A new method to prepare radiation shielding functional aggregate is described, and an appropriate mix ratio and a reasonable calcinated condition was engaged. The y-ray shielding capability of both the new functional aggregates and some other nature aggregates had been measured. The linear attenuation coefficients （μ, cm-1） of these aggregates had been calculated at photon energies from 1 keV to 10GeV using XCOM program, and measured at the photon energies of 662 keV, showing good agreement between experimental and calculated results. The results show that the y-ray shielding capacity of the new functional aggregates has been improved substantially compared with basalt, almost equal to serpentine and high-titanium slag, and up to 80% to barite.

Influence of shielding gas on the mechanical and metallurgical properties of DP-GMA-welded 5083-H321 aluminum alloy

In the present research, 6-mm-thick 5083-H321 aluminum alloy was joined by the double-pulsed gas metal arc welding （DP-GMAW） process. The objective was to investigate the influence of the shielding gas composition on the microstructure and properties of GMA welds. A macrostructural study indicated that the addition of nitrogen and oxygen to the argon shielding gas resulted in better weld penetration. Furthermore, the tensile strength and bending strength of the welds were improved when oxygen and nitrogen （at concentrations as high as approximately 0. 1vol%） were added to the shielding gas; however, these properties were adversely affected when the oxygen and nitrogen contents were increased further. This behavior was attributed to the formation of excessive brown and black oxide films on the bead surface, the formation of intermetallic compounds in the weld metal, and the formation of thicker oxide layers on the bead surface with increasing nitrogen and oxygen contents in the argon-based shielding gas. Analysis by energy-dispersive X-ray spectroscopy revealed that most of these compounds are nitrides or oxides.

Microstructure and pitting corrosion of shielded metal arc welded high nitrogen stainless steel

The present work is aimed at studying the microstructure and pitting corrosion behaviour of shielded metal arc welded high nitrogen steel made of Cromang-N electrode. Basis for selecting this electrode is to increase the solubility of nitrogen in weld metal due to high chromium and manganese content. Microscopic studies were carried out using optical microscopy(OM) and field emission scanning electron microscopy(FESEM). Energy back scattered diffraction(EBSD) method was used to determine the phase analysis, grain size and orientation image mapping. Potentio-dynamic polarization testing was carried out to study the pitting corrosion resistance in aerated 3.5% NaCl environment using a GillAC electrochemical system. The investigation results showed that the selected Cr-Mn-N type electrode resulted in a maximum reduction in delta-ferrite and improvement in pitting corrosion resistance of the weld zone was attributed to the coarse austenite grains owing to the reduction in active sites of the austenite/delta ferrite interface and the decrease in galvanic interaction between austenite and delta-ferrite.

Shielded metal arc welding of cemented carbide to carbon steel

Electrode ENiFe-C1 and E4303 were selected to join the cemented carbide WC-20Co and carbon steel 45 by shielded metal arc welding process. Microstructure and bending property of the corresponding joints were analyzed. The results showed that the carbon steel electrode E4303 had no proper metallurgy condition for the arc welding of cemented carbide and carbon steel. The C and Ni content of the cast iron electrode ENiFe-C1 could meet the condition of preventing the formation ofη carbide,which was suit to the arc welding of cemented carbide and carbon steel,but the operation parameters needed to be optimized to minimize the slag inclusion. The alloy WC-20Co which did not fit for cold arc welding,by adopting the measure of being preheated at 723 K for 1 h before welding,and being kept at 723 K for 3 h after welding then followed furnace cooling could avoid the happening of crack in the WC-20Co base metal.

STUDY ON METAL TRANSFER MODES OF SELF-SHIELDED FLUX-CORED WELDING WIRE

Metal transfer behavior of six kinds of self shielded flux cored wire(SSFCW) is studied using the apparatus of SSFCW high speed photography self made. Six kinds of metal transfer modes of SSFCW were obtained through observation for high speed photograph film and analysis. It is believed that the research is of magnificent for improving operative performance and mechanical properties of SSFCW and dynamics characteristic of welding power.

双氢氧化物修饰镍金属网提升电磁屏蔽性能

针对镍金属网在电磁屏蔽中的低吸收效能(SE_(A))和较高反射(SE_(R))问题,通过电沉积方法在镍金属网(NM)表面负载镍铁双氢氧化物(NiFe LDH)纳米片,旨在提升材料的以吸收为主的屏蔽性能。处理后材料的微观结构和电磁特性得到显著改善,尤其是在X波段内实现了优异的56 dB的SE_(A)和2 dB的SE_(R)。同时,NiFe LDH纳米片优化了介电常数、磁导率、衰减常数和阻抗匹配,证明其在电磁屏蔽领域的广泛应用前景,合成简单且成本效益高。

基于液态金属的纤维复合材料应用研究进展

液态金属(LM)是一种兼具导电性与流动性的功能材料,因其优异的电导率以及形变能力而获得广泛关注。纤维材料作为常见的柔性基底,因其良好的可拉伸性、透气性以及可编织等特点,已在众多领域展现出广阔的应用潜力。为了解决电子元器件柔性差,难以满足可穿戴、智能化要求,从基体和导电材料出发,利用纤维材料的可拉伸变形、柔性等优势与LM的高导电、室温流动性等特点,制备的LM基纤维复合材料已广泛用于人体运动监测、储能等领域。该文从化学稳定性、电性能及热性能方面总结了液态金属基纤维性能调控策略;重点阐述了LM基纤维复合材料在柔性传感、电磁屏蔽、能量收集与存储方面的研究进展;最后,对其性能改善及当前研究中存在的问题提出了建议,并对未来发展方向进行了展望。

电磁屏蔽镀层及涂层织物的屏蔽机制与研究进展

为了阐明电磁屏蔽镀涂层织物的最新研究成果及难点问题,总结了目前金属镀层与导电涂层方法在织物基电磁屏蔽材料中的应用概况。从电磁屏蔽的基本原理出发,阐述表面金属镀层织物和表面导电涂层织物的制备方法、性能特点及其在实际应用中存在的问题,分析织物表面镀层/涂层的成分和结构对屏蔽反射和屏蔽吸收的影响,概括低反射电磁屏蔽镀涂层织物的设计原则与研究现状,并对其未来发展趋势进行展望,以期为电磁屏蔽织物的研究提供借鉴和参考。

钛型气保护药芯焊丝工艺质量影响因素综述

综述了涉及钛型气保护药芯焊丝工艺质量的影响因素。结果表明,合理选用药芯添加物,严格控制熔敷金属中主要强化元素C、Mn、Si的含量,可以改善焊丝熔滴过渡形态,获得焊丝熔敷金属满意的力学性能。在Ar+CO_(2)二元混合保护气体中,随着CO_(2)含量增大,熔滴过渡形态从轴向变为非轴向滴状排斥过渡,接头的抗拉强度几乎没有影响,但熔敷金属的冲击吸收能明显下降。热输入较大时,焊丝工艺性变差;热输入居中时,焊丝工艺性较好。热输入对焊丝熔敷金属韧性的影响出现了对热输入敏感和不敏感两种情况。钛型气保护药芯焊丝工艺质量的三个影响因素控制原理各具特色。

玻璃基中子及γ射线屏蔽材料研究进展

玻璃材料具备高化学稳定性和高辐照稳定性,同时还具备高折射率以及高透光性的光学特性,这使玻璃基中子及γ射线屏蔽材料有望成为同时实现辐射屏蔽以及视觉监控的独特材料。本文从中子辐射及γ射线辐射屏蔽机理入手,结合蒙特卡罗法介绍了屏蔽材料设计思路及手段,以及多种玻璃基屏蔽材料研究现状。铅玻璃由于高毒性正逐步被淘汰,而硅酸盐、硼酸盐、硼硅酸盐等无铅玻璃已成为工业市场的主流。通过向玻璃中掺入重金属化合物(如Bi_(2)O_(3)、BaO)和稀土元素(如La、Gd),可以有效增加质量衰减系数并降低半值层,从而显著提升其屏蔽效果,但是这种掺杂方式可能会对材料的机械性能产生不利影响。此外,本文还比较了玻璃基屏蔽材料与其他类型屏蔽材料的优劣。进一步提升玻璃基屏蔽材料的综合性能,以及开发既环保又智能的新型屏蔽材料,对于推动屏蔽技术的进步与应用具有重大意义。

透明可开关的超宽带频率选择表面电磁屏蔽研究

高频电磁波主要通过玻璃门窗进入建筑物内部,设计具有光学透明且屏蔽功能可开关的超宽带电磁屏蔽体,对同时需要电磁安全和采光的特定场所具有重要工程应用价值.本文利用液态金属的流动性,提出了一种透明可开关电磁屏蔽体的设计新思路.利用液态金属流动性作为电磁屏蔽的切换开关,利用其导电性及Ω型频率选择表面(FSS)结构设计实现超宽带电磁屏蔽.该FSS结构由三层透明材料构成,中间层为聚甲基丙烯酸甲酯(PMMA),顶层和底层为聚二甲基硅氧烷(PDMS),且其中嵌有正交排列的Ω型微通道.通过对微通道中注入液态金属,可将该FSS结构的频率响应从全通状态切换到带阻状态.双层Ω型微通道设计可增强液态金属的流动性并减半其用量,同时实现18.1 GHz以下(覆盖P,L,S,C,X和Ku波段)超宽带电磁干扰抑制,且具有高达80°的极化角度稳定性.所设计的FSS电磁屏蔽结构单元81%的面积未覆盖金属,可获得良好的光学透明性.通过仿真计算TE和TM两种极化方式下的反射系数和吸收率,深入分析了所设计结构的超宽阻带和高角度稳定性机理.对所设计结构进行制备和实验测试,测试结果与仿真结果基本吻合,验证了所设计FSS结构的超宽带电磁屏蔽性能.

压力管道工程中有关焊接诸多认知误区和盲区浅析(二)——焊接工艺和焊接材料

结合国内工业压力管道焊接的现实情况,对焊接工艺评定、焊接方法、焊接材料、保护气体,预热和层间温度控制、焊后热处理以及焊补的补充规定。两大类异种金属焊接的特点和规律,以及P No.1~PNo.5与奥氏体不锈钢和镍基合金之间的异类异种钢坡口对接焊缝的焊接。

电磁屏蔽材料的耐腐蚀研究进展

在恶劣的工作环境中,电磁屏蔽材料的腐蚀问题是制约其服役寿命和服役安全性的关键因素。本文综述了近年来电磁屏蔽材料的耐腐蚀研究现状,主要包括用于电磁屏蔽的金属材料、导电聚合物材料以及柔性材料。首先概述了金属合金和金属镀层的制备方法和防腐机理。其次,在导电聚合物材料方面,主要探讨了掺杂型和本征导电型聚合物电磁屏蔽材料的制备工艺、存在的问题及防腐设计方案。此外,介绍了柔性织物和柔性薄膜作为耐腐蚀电磁屏蔽材料的主要研究成果。最后,对电磁屏蔽材料的耐腐蚀研究前景进行了展望。

液态金属/硅橡胶复合材料的应用研究进展

综述了三种功能化液态金属/硅橡胶复合材料包括导热复合材料、电磁屏蔽复合材料和柔性导电复合材料,介绍了复合材料的制备方法以及导热、导电、电磁屏蔽和力学性能,阐述了该复合材料在柔性导热界面材料、电磁屏蔽系统和可穿戴电子产品等方面的应用,并展望了其发展方向。

超薄金属基电磁屏蔽玻璃研究进展

电磁屏蔽玻璃是国防、民生等领域的重要应用材料,但是电磁性能和光学性能往往难以兼顾提升。超薄金属基透明电磁屏蔽薄膜是电磁屏蔽玻璃领域常用的功能性材料。本文对超薄金属基电磁屏蔽玻璃的屏蔽设计原理进行了详细阐述,重点综述了降低超薄金属薄膜阈值厚度的方法,回顾了近年来不同结构的超薄金属基电磁屏蔽玻璃的光学及电磁屏蔽性能,并对电磁屏蔽玻璃的未来发展趋势进行了讨论。

中压电力电缆金属屏蔽层截面积的计算方法探析

中压电力电缆金属屏蔽的实施方式分为铜带绕包屏蔽和铜丝疏绕屏蔽,其截面积的大小是根据故障电流容量要求设定的,不同金属屏蔽的截面积的计算方法不一样,按照国家标准中计算出的金属屏蔽的实际截面跟要求设定的数据存在偏差,可能会造成安全隐患或质量过剩。通过实例比较得出了两种屏蔽方式截面积合理的计算方法,为中压电力电缆金属屏蔽的工艺设计提供参考依据。