Stress Analysis of Printed Circuit Board with Different Thickness and Composite Materials Under Shock Loading

In this study,the deformation and stress distribution of printed circuit board(PCB)with different thickness and composite materials under a shock loading were analyzed by the finite element analysis.The standard 8-layer PCB subjected to a shock loading 1500 g was evaluated first.Moreover,the finite element models of the PCB with different thickness by stacking various number of layers were discussed.In addition to changing thickness,the core material of PCB was replaced from woven E-glass/epoxy to woven carbon fiber/epoxy for structural enhancement.The non-linear material property of copper foil was considered in the analysis.The results indicated that a thicker PCB has lower stress in the copper foil in PCBs under the shock loading.The stress difference between the thicker PCB(2.6 mm)and thinner PCB(0.6 mm)is around 5%.Using woven carbon fiber/epoxy as core material could lower the stress of copper foil around 6.6%under the shock loading 1500 g for the PCB with 0.6 mm thickness.On the other hand,the stress level is under the failure strength of PCBs with carbon fiber/epoxy core layers and thickness 2.6 mm when the peak acceleration changes from 1500 g to 5000 g.This study could provide a reference for the design and proper applications of the PCB with different thickness and composite materials.

Material Photos of IJO/IES Editorial Board Meeting

Date:Sept.18,2014 Venue:Xi’an,ChinaWelcome to IJO Editorial Board Meeting and IJO ReceptionSpecial Members Attending the IJO Meeting Prof.Bruce Spivey,Immediate Past President of ICO Prof.Mark Tso,Former Vice President of ICO Prof.Rajvardhan Azad,President of APAO Prof.Chi-Chao Chan,NEI of the U.S.National Institutes of Health Prof.William Smiddy,Bascom Palmer Eye Institute,USA

Material Photos of IJO/IES Editorial Board Meeting

Date:Sept.18,2014Venue:Xi’an,China Special Members Attending the IJO Meeting Prof.Bruce Spivey,Immediate Past President of ICO Prof.Mark Tso,Former Vice President of ICO Prof.Rajvardhan Azad,President of APAO Prof.Chi-Chao Chan,NEI of the U.S.National Institutes of Health Prof.William Smiddy,Bascom Palmer Eye Institute,USA Academician Li-Xin Xie,Honorary President of Chinese Ophthalmology Society Prof.Hao Cui,President of Ophthalmological Society,Chinese Association of Intergative Medicine

Developments and Prospects of Long-Span High-Speed Railway Bridge Technologies in China

With the rapid developments of the high-speed railway in China, a great number of long-span bridges have been constructed in order to cross rivers and gorges. At present, the longest main span of a constructed high-speed railway bridge is only 630 m. The main span of Hutong Yangtze River Bridge and of Wufengshan Yangtze River Bridge, which are under construction, will be much longer, at 1092 m each. In order to overcome the technical issues that originate from the extremely large dead loading and the relatively small structural stiffness of long-span high-speed railway bridges, many new technologies in bridge construction, design, materials, and so forth have been developed. This paper carefully reviews progress in the construction technologies of multi-function combined bridges in China, including com- bined highway and railway bridges and multi-track railway bridges. Innovations and practices regarding new types of bridge and composite bridge structures, such as bridges with three cable planes and three main trusses, inclined main trusses, slab-truss composite sections, and steel-concrete composite sections, are introduced. In addition, investigations into high-performance materials and integral fabrication and erection techniques for long-span railway bridges are summarized. At the end of the paper, prospects for the future development of long-span high-speed railwav bridges are provided.

Development of High-Speed On-Of Valves and Their Applications

With the widespread application of the computer and microelectronic technology in the industry,digitization becomes the inevitable developing trend of the hydraulic technology.Digitization of the hydraulic components is critical in the digital hydraulic technology.High-speed on-of valves(HSVs)which convert a train of input pulses into the fast and accurate switching between the on and of states belong to widely used basic digital hydraulic elements.In some ways,the characteristics of the HSVs determine the performance of the digital hydraulic systems.This paper discusses the development of HSVs and their applications.First,the HSVs with innovative structures which is classifed into direct drive valves and pilot operated valves are discussed,with the emphasis on their performance.Then,an overview of HSVs with intelligent materials is presented with considering of the switching frequency and fow capacity.Finally,the applications of the HSVs are reviewed,including digital hydraulic components with the integration of the HSVs and digital hydraulic systems controlled by the HSVs.

Fracture Analysis of Composites in High-speed Tension

In this paper the results of a high-speed tension experiment of the SiC_w/Al composite have been reported and a simplified theoretical model has been developed to study the fracture mechanism of composites in high-speed tension. This theoretical model provides a new explanation for the increase of dynamic fracture strength of composites in high-speed tension.

Investigation of insulation layer dynamic characteristics for high-speed railway

Dynamic performance of insulation is one of the key parameters during the insulation application for high-speed railway subgrade. This paper conducted laboratory and field tests for the materials and dynamic load, especially for thermal performance, elastic deformation, and accumulated deformation of insulation materials. Experiment results show that mechanical properties of insulation layer structure are stable, which satisfies the requirements of the high speed railway.

Development and Characterization of Particle Boards Based on Sorghum Husk

This study tackles current environmental challenges by developing innovative and eco-friendly particle boards utilizing sorghum husk, combined with recycled expanded polystyrene (EPS). This dual eco-responsible approach valorizes sorghum husk, often deemed agricultural waste, and repurposes EPS, a plastic waste, thus contributing to CO2 emission reduction and effective waste management. The manufacturing process involves dissolving recycled polystyrene within a solvent to create a binder, which is then mixed with sorghum husk and cold-pressed into composite boards. The study explores the impact of two particle sizes (fine and coarse) and two different concentrations of the recycled EPS binder. Results demonstrate significant variations in the boards’ mechanical properties, displaying a range of Modulus of Rupture (MOR) from 0.84 MPa to 3.85 MPa, and Modulus of Elasticity (MOE) spanning from 658.13 MPa to 1313.25 MPa, influenced by the binder concentration and particle size. These characteristics suggest that the boards can be effectively used in various construction applications, including interior decoration, false ceilings, and potentially for furniture and door manufacturing when combined with appropriate coatings. This study not only exemplifies the valorization of plastic and agricultural wastes but also offers a practical, localized solution to global climate change challenges by promoting sustainable construction materials.

建筑节能材料在室内装饰工程中的应用研究

随着人们环境保护意识的提升和节能减排政策的推动,建筑节能材料在室内装饰工程中的应用日益广泛。文章研究了常见建筑节能材料的类型、特性以及在室内装饰工程中的具体应用方法,包括聚苯乙烯泡沫板、挤塑聚苯乙烯泡沫板、矿物棉、聚氨酯泡沫和膨胀珍珠岩等常见材料在实际工程中的安装流程和技术要点,同时分析了这些材料对环境的影响和经济效益,以供参考。

建筑屋面防水节能保温系统用材优化与结构设计

以重庆等南方地区为例,探讨建筑用真空绝热复合保温防水胶材料工程应用技术与实践。选择保温板粘贴的薄抹灰系统,保证基层墙体和真空绝热板粘贴面积必须在80%以上,以提高基层墙体和该系统板材表面拉伸粘接强度。应用保温浆料真空绝热板建筑外墙外保温系统,组成成分包括抹面胶浆、粘接砂浆、保温浆料、真空绝热板和饰面材料等,应用在建筑物外墙外侧。真空绝热板必须借助密封性才能实现其低导热与真空性能,钻孔裁切后,会降低其真空度,进而对绝热板保温性能产生影响。采用硅钙板夹芯绝热板+现浇混凝土保温系统、钢丝网框保温抗裂浆料夹芯绝热板及钢板网夹芯真空绝热板墙体保温系统结构设计。结果显示:复合绝热板可有效改善保温系统构件的拉伸粘接性能,大大提升系统的抗冲击性及节能保温效果。

Energy field-assisted high-speed dry milling green machining technology for difficult-to-machine metal materials

Energy field-assisted machining technology has the potential to overcome the limitations of machining difficult-to-machine metal materials,such as poor machinability,low cutting efficiency,and high energy consumption.High-speed dry milling has emerged as a typical green processing technology due to its high processing efficiency and avoidance of cutting fluids.However,the lack of necessary cooling and lubrication in high-speed dry milling makes it difficult to meet the continuous milling requirements for difficult-to-machine metal materials.The introduction of advanced energy-field-assisted green processing technology can improve the machinability of such metallic materials and achieve efficient precision manufacturing,making it a focus of academic and industrial research.In this review,the characteristics and limitations of high-speed dry milling of difficult-to-machine metal materials,including titanium alloys,nickel-based alloys,and high-strength steel,are systematically explored.The laser energy field,ultrasonic energy field,and cryogenic minimum quantity lubrication energy fields are introduced.By analyzing the effects of changing the energy field and cutting parameters on tool wear,chip morphology,cutting force,temperature,and surface quality of the workpiece during milling,the superiority of energy-field-assisted milling of difficult-to-machine metal materials is demonstrated.Finally,the shortcomings and technical challenges of energy-field-assisted milling are summarized in detail,providing feasible ideas for realizing multi-energy field collaborative green machining of difficult-to-machine metal materials in the future.

High-speed imaging observation on molten bridges of AgNi10 electrical contact material

The electrical contact-high-speed imaging experimental system was developed to investigate the molten bridge phenomena of AgNi10 electrical contact material.The dimension of molten bridges was measured along with the measurement of waveforms in the contact voltage under the load of direct current(DC) 6 V(8-20 A)and breaking speed of 50.0 mm·s^(-1).A part of the observed results was presented as well as surface morphology of the contacts after electrical contact behavior,which shows some interesting and new phenomena.Molten bridges and arc could exist simultaneously.The stable molten bridge looks like cylindrical shape and then becomes needle tip at its rupture,the diameter and length of molten bridges both increase with the increase in current and the growth gradient of the diameter is larger than that of the length.The morphology and elemental distribution of the contact surface are changed by the behavior of electrical contact.

Modeling of Micropores Drilling Force for Printed Circuit Board Micro-holes Based on Energy Method

The quality of printed circuit board(PCB)micro-hole processing directly determines the stability of the inner and outer circuit connections.Micro-hole drilling technology is a typical method for PCB micro-hole processing.The problem of optimal control of its drilling force is one of the main factors affecting the quality of micro-hole machining.To address this problem,the thrust forces and torques in PCB drilling were first modeled and analyzed,and the corresponding prediction models were established.The drilling force analysis was carried out through the micro-hole drilling experiment,the specific cutting energy under different feed rates was calculated,the influence of the size effect was clarified,and the accuracy of the prediction model was verified.The result shows that during the drilling of glass fiber cloth,changes in the material removal mechanism are induced as the feed per revolution is varied.When the feed per revolution is less than the tool edge radius,the glass fiber is not cut by the main cutting edge,but is crushed and broken.When the feed per revolution is greater than the radius of the tool edge,the glass fiber is cut by the main cutting edge.At the same time,the established analytical model can accurately reflect the influence of the size effect on the drilling torque in PCB micro-hole drilling,and the error is within 10%.This method has certain practical application value in controlling PCB micro hole processing quality.

六水合氯化钙基相变材料对岩棉保温板储能和保温性能的影响

以岩棉板为载体,将自主研制的六水合氯化钙基相变储能材料均匀渗入到岩棉板,制备了六水合氯化钙基相变材料改性的岩棉/六水合氯化钙基保温墙板,研究了六水合氯化钙基相变材料对岩棉板储能隔热能力及其力学强度的影响.结果表明:相变材料加入赋予了岩棉吸热储能性能,使岩棉板保温性能得到提高.岩棉板对六水合氯化钙基相变材料的最大吸附量为30 wt.%,且该吸附量下的保温岩棉墙板显示出最大的比热容0.7001 MJ/(m^(3)·K).尽管该吸附量下复合板显示较大的导热系数0.0891 W/(m·K),但其相应热扩散率却最小,为0.1273 mm^(2)/s.热温度测试表明该吸附量下室内最高温度降幅达到3.4℃,表明导热系数不是影响岩棉板保温性能的唯一因素,采用热扩散率评估其保温性能更为合理.SEM显示六水合氯化钙基相变材料黏附于岩棉纤维之间且形成了稳定的空间网格架构,有效提高了岩棉板的抗压强度.

稀土铝酸锶发光材料与刨花热压成型工艺研究

采用定向刨花板生产工艺,把稀土铝酸锶长余辉发光材料按不同方式、不同比例加入刨花中,通过热压成型,测试加入稀土铝酸锶发光材料的刨花板材发光性能、力学性能,研究刨花-稀土铝酸锶复合发光材料的成型技术。结果表明:稀土铝酸锶与刨花最优混合比例为1∶15;测试成型后的稀土铝酸锶发光刨花板物理力学性能优于GB/T41715—2022中干燥状态下非承载型定向刨花板;稀土铝酸锶发光刨花板的发光强度在黑暗环境下由高到低再到稳定状态,初步余晖试验在日照3小时后在黑暗环境下余晖效应能达到12小时以上,满足稀土铝酸锶发光刨花板在室内外建筑及各使用领域中的应用效果。

High-Speed Rubbing Behavior of Abrasive Coating Coated on Titanium Alloy Blade Tips

In aero-engines, abrasive coatings are typically utilized to protect the blade tip from excessive wear caused by the harder abradable sealing coating and thereby improve the sealing performance of engines. Therefore, a Ni/cBN abrasive coating was prepared on titanium alloy using electrodeposition. The high-speed rubbing tests with a linear velocity of 350 m/s and different incursion rates were performed to investigate the effect of the Ni/cBN abrasive coating on the wear behavior against NiCrAl/diatomite seal coating. Results showed that melting wear and adhesive transfer occurred on the bare blades, causing the bare blade to suffer excessive wear. While the Ni/cBN abrasive coating exhibited superior wear resistance and cutting performance. The cBN grits pullout, the abrasion of Ni matrix and transfer of seal coating to the cBN grits were the main wear mechanism of the Ni/cBN abrasive coating. Additionally, it was found that the relationship between the incursion rate and high-speed rubbing behavior is quite different for the bare blade and Ni/cBN coating. The reason for the difference in wear behavior of bare blade and Ni/cBN coating at different incursion rates was discussed in detail.

移动通讯用低介电塑料基材的研究进展

纵观移动通讯的发展史,从最开始的有线、低频低速通讯到如今的无线、高频高速通讯,随着通讯行业的发展,对移动通讯的关键元件—印制电路板(PCB)的要求也逐渐提高。因此,开发低介电常数,低介电损耗,良好的耐热、尺寸稳定性的高分子PCB板尤为重要。本文主要介绍市场上的应用高频PCB低介电高分子材料,并重点阐述环氧树脂(EP),聚酰亚胺(PI),聚四氟乙烯(PTFE),液晶聚合物(LCP)用作PCB的优缺点及对其改性的研究情况。

雷达隐身措施对Caret进气道性能影响的数值计算

针对S弯Caret进气道气动与电磁散射特性研究,采用多层快速多极子(MLFMM)数值计算方法,对比分析了转子叶片转动相位角变化对进气道雷达散射截面(RCS)的影响。采用剪切应力输运(SST) k-ω湍流模型求解N-S方程,计算黏性流场并分析进气道气动性能,对比分析了扩压段的构型和吸波导流板的安装方式对进气道气动与雷达隐身性能的影响。结果表明:转子叶片相位角的变化会导致进气道RCS在同一雷达波入射角度下出现变动,但不会改变RCS随雷达波入射角度的变化规律;采用双S弯扩压段可以有效降低进气道出口畸变和提升Caret进气道的雷达隐身性能,使其在2种工况下平均RCS均小于-2 dB,由叶片旋转导致的RCS最大差值均小于-3.5 dB,但也会导致进气道临界压力的降低;安装合适的吸波导流板可以有效提升进气道的雷达隐身性能,但会造成进气道出口畸变的增加。