Capillary Property of Entangled Porous Metallic Wire materials and Its Application in Fluid Buffers:Theoretical Analysis and Experimental Study

Strong impact does serious harm to the military industries so it is necessary to choose reasonable cushioning material and design effective buffers to prevent the impact of equipment.Based on the capillary property entangled porous metallic wire materials(EPMWM),this paper designed a composite buffer which uses EPMWM and viscous fluid as cushioning materials under the low-speed impact of the recoil force device of weapon equipment(such as artillery,mortar,etc.).Combined with the capillary model,porosity,hydraulic diameter,maximum pore diameter and pore distribution were used to characterize the pore structure characteristics of EPMWM.The calculation model of the damping force of the composite buffer was established.The low-speed impact test of the composite buffer was conducted.The parameters of the buffer under low-speed impact were identified according to the model,and the nonlinear model of damping force was obtained.The test results show that the composite buffer with EPMWM and viscous fluid can absorb the impact energy from the recoil movement effectively,and provide a new method for the buffer design of weapon equipment(such as artillery,mortar,etc.).

Mechanical behavior of entangled metallic wire materials-polyurethane interpenetrating composites

Composite materials exhibit the impressive mechanical properties of high damping and stiffness,which cannot be attained by employing conventional single materials.Along these lines,a novel material architecture is presented in this work in order to fabricate composites with enhanced mechanical characteristics.More specifically,entangled metallic wire materials were used as the active matrix,whereas polyurethane was employed as the reinforcement elements.As a result,an entangled metallic wire material-polyurethane composite with high damping and stiffness was prepared by enforcing the vacuum infiltration method.On top of that,the mechanical properties(loss factor,energy consumption,and average stiffness)of the proposed composite materials were characterized by performing dynamic tests,and its fatigue characteristics were verified by the micro-interface bonding,as well as the macro-damage factor.The impact of the density,preloading spacing,loading amplitude,and exciting frequency on the mechanical properties of the composites were also thoroughly analyzed.The extracted results indicate that the mechanical properties of the composites were significantly enhanced than those of the pure materials due to the introduction of interface friction.Moreover,the average stiffness of the composites was about 10 times the respective value of the entangled metallic wire material.Interestingly,a rise in the loading period leads to some failure between the composite interfaces,which reduces the stiffness property but enhances the damping dissipation properties.Finally,a comprehensive dynamic mechanical model of the composites was established,while it was experimentally verified.The proposed composites possess higher damping features,i.e.,stiffness characteristics,and maintain better fatigue characteristics,which can broaden the application range of the composites.In addition,we provide a theoretical and experimental framework for the research and applications in the field of metal matrix composites.

Quasi-static and low-velocity impact mechanical behaviors of entangled porous metallic wire material under different temperatures

To improve the defense capability of military equipment under extreme conditions,impact-resistant and high-energy-consuming materials have to be developed.The damping characteristic of entangled porous metallic wire materials(EPMWM)for vibration isolation was previously investigated.In this paper,a study focusing on the impact-resistance of EPMWM with the consideration of ambient temperature is presented.The quasi-static and low-velocity impact mechanical behavior of EPMWM under different temperatures(25℃-300℃)are systematically studied.The results of the static compression test show that the damping energy dissipation of EPMWM increases with temperature while the nonlinear damping characteristics are gradually enhanced.During the impact experiments,the impact energy loss rate of EPMWM was between 65%and 85%,while the temperatures increased from 25℃to 300℃.Moreover,under the same drop impact conditions,the overall deformation of EPMWM decreases in the temperature range of 100℃-200℃.On the other hand,the impact stiffness,energy dissipation,and impact loss factor of EPMWM significantly increase with temperature.This can be attributed to an increase in temperature,which changes the thermal expansion coefficient and contact state of the internal wire helixes.Consequently,the energy dissipation mode(dry friction,air damping,and plastic deformation)of EPMWM is also altered.Therefore,the EPMWM may act as a potential candidate material for superior energy absorption applications.

Numerical and experimental evaluation for density-related thermal insulation capability of entangled porous metallic wire material

Entangled porous metallic wire material(EPMWM)has the potential as a thermal insulation material in defence and engineering.In order to optimize its thermophysical properties at the design stage,it is of great significance to reveal the thermal response mechanism of EPMWM based on its complex structural effects.In the present work,virtual manufacturing technology(VMT)was developed to restore the physics-based 3D model of EPMWM.On this basis,the transient thermal analysis is carried out to explore the contact-relevant thermal behavior of EPMWM,and then the spiral unit containing unique structural information are further extracted and counted.In particular,the thermal resistance network is numerically constructed based on the spiral unit through the thermoelectric analogy method to accurately predict the effective thermal conductivity(ETC)of EPMWM.Finally,the thermal diffusivity and specific heat of the samples were obtained by the laser thermal analyzer to calculate the ETC and thermal insulation factor of interest.The results show that the ETC of EPMWM increases with increasing temperature or reducing density under the experimental conditions.The numerical prediction is consistent with the experimental result and the average error is less than 4%.

Analysis of metal transfer during electron beam welding with filler wire

The metal transfer mode of electron beam welding （EBW） with filler wire was studied experimentally. The spatial position between the electron beam and the filler wire was defined. Basing on the charge coupled device （CCD） visual sensing system, the metal transfer mode of filler wire was investigated. The results showed that there were five transfer modes during EBW process due to different wire feed rates and spatial positions between beam and filler wire, such as short-circuiting mode, molten metal bridge mode, small droplet mode, big droplet mode and mixed mode. By comparing the weld appearance of different transfer modes, the molten metal bridge transfer was proved to be the best transfer mode.

Wire and arc additive manufacturing of 4043 Al alloy using a cold metal transfer method

Cold metal transfer plus pulse(C+P)arc was applied in the additive manufacturing of 4043 Al alloy parts.Parameters in the manufacturing of the parts were investigated.The properties and microstructure of the parts were also characterized.Experimental results showed that welding at a speed of 8 mm/s and a wire feeding speed of 4.0 m/min was suitable to manufacture thin-walled parts,and the reciprocating scanning method could be adopted to manufacture thick-walled parts.The thin-walled parts of the C+P mode had fewer pores than those of the cold metal transfer(CMT)mode.The thin-and thick-walled parts of the C+P mode showed maximum tensile strengths of 172 and 178 MPa,respectively.Hardness decreased at the interface and in the coarse dendrite and increased in the refined grain area.

Surface plasmon wave propagation along single metal wire

Recently, the single metal wire （SW） has become attractive for its potential applications in the terahertz and higher frequency range. However, as the most simple and typical surface plasmon polariton （SPP） transmission line, its study seems far from enough. Many important transmission behaviours have not been explained satisfactorily from the viewpoint of physics. In this paper, making use of the modified Drude model （MDM） based on the Sommerfeld theory, the transmission behaviours of SPPs along SW are systemically investigated theoretically. Some important physical phenomena such as the mode transformation, the lifetime of the radiative mode and the resonance frequency are revealed, and their mechanisms are explored. The results obtained in the paper will facilitate a general understanding of the features and the physical essence of the SPP transmission, not only for SW itself but also for other SPP transmission lines.

Inclusion behavior and microstructure of weld metal with Ce in twin wire high heat input submerged-arc welding

In this study,the welding thermal cycle curve exhibited two temperature peaks in high heat-input twin-wire separate-pool submerged-arc welding and coarse-grained heat affected zone existed in the welded joint. The inclusions of primary weld metal and coarse-grained heat affected zone of Ce-added SAW should be Al_2O_3,MnO,SiO_2,TiO,Ce_2S_3,CeS,Ce_2O_2S and Ce_2O_3. Under the effect of welding thermal cycle,oxy-sulfides inclusions of Ce,the diameter of which was less than 2. 0 μm,slightly grew larger,but the composition and type of the inclusions didn't change. The microstructure of the large heat input weld metal had acicular ferrite that Ce oxide sulphide particles induced nucleation and proeutectoid ferrite. In the coarse-grained heat affected zone of weld metal,home-position precipitation of acicular ferrite and sympathetic acicular ferrite were both observed. It was supposed that previous crystal cells of acicular ferrite in austenite grain promoted home-position precipitation of acicular ferrite. Meanwhile,sympathetic acicular ferrite tended to nucleate at the primary acicular ferrite grain boundaries,where high dislocation density was located,and grew inside the neighboring carbon-depleted austenitic regions. The granular bainite nucleated in the austenitic zone with high carbon content close to acicular ferrite and sympathetic acicular ferrite.

Effect of the wire preheating transfer in GMAW temperature on the metal with thick wire

A hot-wire gas metal arc welding （GMAIV） method using a TIG arc to preheat the wire was proposed and a corresponding experimental system was developed. The images of molten metal droplets in GMA W with thick-wire diameter of 3.2 mm were captured by a high-speed camera, and the influence of the wire temperature on metal transfer was analyzed by measurements of droplet radius and transfer frequency. Two metal transfer modes were mentioned in this paper： the short- circuit transfer and the globular transfer mode. The results demonstrate that the wire temperature significantly impacts the metal transfer mode, droplet size and transfer rate at a certain welding current range. And with the increasing wire temperature, the change of metal transfer mode was observed. By increasing the temperature of the welding wire, the droplet size decreases and the droplet transfer frequency increases accordingly. In addition, it is important that the drop spray mode, which hardly occurs in GMAW with steel wire, was obtained by means of increasing the wire temperature.

Measurement of electrical conductivity of micron-scale metallic wires

Electrical conductivities of micron-scale aluminum wires were quantitatively measured by a four-point atomic force microscope (AFM) probe. This technique is a combination of the principles of the four-point probe method and standard AFM. This technique was applied to the 99.999% aluminum wires with 350 nm thickness and different widths of 5.0, 25.0 and 50.0μm. Since the small dimensions of the wires, the geometrical effects were discussed in details. Experiment results show that the four-point AFM probe is mechanically flexible and robust. The four-point AFM probe technique is capable of measuring surface topography together with local electrical conductivity simultaneously. The repeatable measurements indicate that this technique could be used for fast in-situ electrical properties characterization of sensors and microelectromechanical system devices.

Study on response of metal wire in thermoacoustic imaging

Thermoacoustic imaging(TAI)is an emerging high-resolution and high-contrast imaging technology.In recent years,metal wires have been used in TAI experiments to quantitatively evaluate the spatial resolution of different systems.However,there is still a lack of analysis of the response characteristics and principles of metal wires in TAI.Through theoretical and simulation analyses,this paper proposes that the response of metal(copper)wires during TAI is equivalent to the response of antennas.More critically,the response of the copper wire is equivalent to the response of a half-wave dipole antenna.When its length is close to half the wavelength of the incident electromagnetic wave,it obtains the best response.In simulation,when the microwave excitation frequencies are 1.3 GHz,3.0 GHz,and 5.3 GHz,and the lengths of copper wires are separately set to 11 cm,5 cm,and 2.5 cm,the maximum SAR distribution and energy coupling effciency are obtained.This result is connected with the best response of half-wave dipole antennas with lengths of 11 cm,4.77 cm,and 2.7 cm under the theoretical design,respectively.Regarding the further application,TAI can be used to conduct guided minimally invasive surgery on surgical instrument imaging.Thus,this paper indicated that results can also guide the design of metal surgical instruments utilized in different microwave frequencies.

Empirical Model for Evaluating Covered Effect on Polyimide/Metal Wire Cowrapped Yarn by Response Surface Methodology

To accurately evaluate and predict the covered effect of cowrapped yarn,a novel characterization is performed by covered ratio and fineness. Polyimide / metal wire co-wrapped yarn which was designed for applications in aerospace and composites was developed through hollow spindle spinning process. Core yarn speed,hollow spindle rotating speed,and wrapping yarn twist were selected as three main factors that affected spinning process. An empirical model indicating relationship between spinning parameters and covered effect was established based on response surface methodology( RSM). The results show that wrapping yarn twist contributes greatly to smooth wrapping process. Core yarn speed and spindle rotating speed are significant impact factors of covered effect and they interact significantly in covered ratio, but indistinctively in fineness.

The Effect of Nanometer Size Effect on the Optical Property of Metallic Wire Grid

We mainly investigated the effect of metallic wire grid on its optical property. At first, we give one simple model to deduce an expression which can describe the relationship of the optical property with the width of metallic wire grid. This expression could be used to calculate the reflectance of the metallic wire grid. We also give the corresponding computer simulation. Our simulation shows that the reflectance would increase when the width of metallic wire grid increase. The wider the metallic wire grid is, the higher the reflectance is. The reflectance would reach the maximum value only when the width is over the free path of electronic.

Difference in particle characteristics and coating properties between spraying metallic and ceramic powder cored wires

The sprayed particles of metallic and cermet wires were collected to analyze the atomization state of the particles in arc spraying forming, the microstructure and properties of metallic and ceramic coatings were investigated and compared. Particle size analyzer was used for quantifying particle size. The XRD, SEM and optical microscope(OM) were used to analyze the phase composition and microstructure of the particles and coatings. From the experimental results, some difference of particle characteristics was established between the spraying metallic and ceramic cored wires, and the microstructure and properties of coatings depend strongly on the particles behaviors. The result shows that Fe-TiB2/Al2O3 composite coating has a high potential for abrasive wear applications.

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.

大型双板导波天线对核电磁脉冲传输损耗和畸变特性

大型导波核电磁脉冲模拟器可为系统级装备试验提供自由空间辐照环境。针对此类模拟器常用的双板导波天线可能存在的传输损耗和波形畸变问题,以电磁仿真软件和算例对比分析研究了3种主要的影响因素,包括土壤的介电损耗及其抑制、前锥板向平行板转折的结构不连续、线栅阵列代替金属板的缝隙泄漏。研究结果表明:对上下极板等宽的情形,土壤损耗可使电压传输效率降低25%以上;适当展开下极板宽度可屏蔽土壤损耗;上极板转折处的结构不连续可导致平行段试验空间内电场呈现双峰交叠、幅度降低、波形畸变等特征;最大线间距0.3 m不会导致前沿显著变化。作为工程应用案例,设计了前锥长度60 m、顶高15 m、下极板拓宽3 m、由100根线栅阵列构成上极板的导波天线,试验空间超过20 m×20 m×10 m,实现了前沿2.5~3.0 ns双指数脉冲的无损耗、无畸变传输。

基于工程应用的CW-GMAW熔滴过渡形态表征

综述了涉及工程应用的冷丝熔化极气体保护焊(Cold wire gas metal arc welding,CW-GMAW)熔滴过渡形态特征。结果表明,在大电流、强规范、富氩混合气体保护下,CW-GMAW工艺的熔滴过渡形态呈喷射过渡;当电流较小、电弧电压较低时,可能为滴状过渡,甚至在弧压很低时,呈现短路过渡形态。该工艺电弧发生偏向冷丝的位移,弧长变短甚至发生短路,与冷丝送进速率比增高及冷丝在电弧中产生大量金属蒸气时弧柱电阻下降有关。在具有富氩混合保护气体的相同工艺参数下,CWGMAW转变电流比GMAW降低了4%~7%。焊接工艺参数对CW-GMAW和GMAW工艺熔滴过渡形态的影响规律大致相近,但前者因涉及冷丝送进速率比和电极焊丝送进速度,以及它们的匹配等,使焊接电流的影响更为复杂。

金属橡胶复合隔振器的动静态性能

设计一种对称式金属橡胶与线弹簧复合的隔振器,基于整体隔振,考虑安装板的柔性因素,建立相应的等效线性动力学模型.通过准静态力学试验,分析线弹簧刚度、金属橡胶密度和加载位移对金属橡胶复合隔振器准静态性能的影响.同时,进行随机振动试验,研究金属橡胶复合隔振器在整体隔振中的隔振性能.试验结果表明,复合样件的刚度特性趋向于线性效果.金属橡胶复合隔振器在谐振点处的峰值衰减是线弹簧隔振器的5倍以上,且系统的随机振动响应在频段0.12~2.00 kHz内都有较大程度的衰减.

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。

金属橡胶-聚氨酯复合材料减振性能研究

针对单一减振材料无法兼具高阻尼与高刚度的弊端,本工作提出了一种新的复合材料,即将三维空间网状结构的金属橡胶(EMWM)作为基体,聚氨酯(PU)作为增强体,并采用真空渗流的方式制备了具有高阻尼与高刚度的金属橡胶-聚氨酯(EMWM-PU)复合材料。通过EMWM与EMWM-PU复合材料的准静态压缩试验,发现界面摩擦的引入使得EMWM-PU复合材料的耗能与刚度特性得到显著提升。此外搭建了复合材料管路减振测试平台,以平均振动加速度级和插入损失作为评价指标,研究了EMWM密度、激振量级、安装时的预紧间距对管路减振性能的影响。结果表明,EMWM-PU复合材料在5~1 000 Hz频段范围内均具有优异的减振效果,且复合材料中基体材料EMEM的密度越小、安装时的预紧间距越大,减振效果越好。本研究有效拓宽了复合材料的应用范围,也为金属橡胶复合材料的设计和应用提供了有效的指导。