Metal Wire Research Articles

Heat and mass transfer in electron beam additive manufacturing

The electron beam wire-feed additive manufacturing (EBAM) technology utilizes a high-energy electron beam as a heat source to bombard a metal wire in the vacuum environment to form a molten pool. The stability and quality of the deposition mainly depend on the transition behavior of the droplet. To conduct this research, a high-fidelity thermo-fluid dynamic simulation model based on the local reconstruction of the 3D model was developed and verified. The model used the Monte-Carlo algorithm to update the scattering trajectories and residual energies of high-energy electrons on the irradiated surface of the wire and molten pool at each time step in the numerical calculation. Quantitatively analyzed the “electron-wire” instantaneous energy coupling mechanism in the droplet transition mode, insertion transition mode, and liquid bridge transition mode, and finally established an energy-matching criterion for maintaining a stable deposited track morphology. The results show that during the initial stage of wire melting, the droplet will climb along the wire feeding direction, grow under gravity, and eventually drop under the combined effects of gravity and recoil pressure. Different forms of molten droplets will form various solidification morphology, with the liquid bridge transition mode being the most desirable. To maintain a stable liquid bridge transition, it is necessary to control the droplet generation height within the range of 0–2.7 mm. The collapse of the deposited track, caused by heat accumulation during the multilayer deposition, would also alter the droplet generation height. Therefore, to maintain the liquid bridge transition mode in the multilayer multi-channel forming process, it is also necessary to ensure that the energy density of the deposited track is slightly greater than 1.16×1010 J/m3 and the energy density of the wire is slightly greater than 2.63×1010 J/m3.

Thermodynamic property of sandwich cylindrical shell structure with metallic wire mesh: Numerical modeling and experimental analysis

As a new addition to lightweight composite structures, the sandwich cylindrical shell with a metallic wire mesh core has emerged as a promising solution for thermodynamic performance analysis at elevated temperatures. The intricate interwoven cellular formations within the metallic wire mesh pose difficulties for thermo-mechanical modeling and property evaluation. First, the constitutive models employed to characterize hysteresis phenomena were presented, comprising isotropic elasticity, Bergstrom-Boyce model, Ogden hyper-elasticity, and parameter identification through mechanical examinations at varying temperatures. Second, the finite element modeling of cylindrical shell structures was determined for modal and steady-state dynamic analyses. Third, the experimental procedures were carried out, including the preparation of the sandwich cylindrical shell and the dynamic testing platform. The first-order natural frequency of the cylindrical shell structure is close to the resonance frequency of the dynamic test results, with a maximum error of 6.5%, demonstrating the accuracy of the simulation model. When compared to the solid-core cylindrical shell, the average insertion loss of the sandwich cylindrical shell structure within the frequency range of 10–1000 Hz at room temperature is up to 11.09 dB. Furthermore, at elevated temperatures, the average insertion loss of the sandwich cylindrical shell decreases but fluctuates as the temperature changes.

РЕШЕНИЕ ВОПРОСА СОВМЕЩЕНИЯ СООСНОСТИ ДВУХ ПЕРЕСЕКАЮЩИХСЯ МЕТАЛЛИЧЕСКИХ ПРОВОЛОК НА ПРИМЕРЕ ИСПЫТАТЕЛЬНОГО СТЕНДА ДЛЯ МЕТАЛЛИЧЕСКОГО НАПЫЛЕНИЯ

In this work, the task was to ensure the alignment of two intersecting metal wires to maintain the welding arc at all times. This need arose as a result of an experiment in cold spray metal plating. It revealed a problem that does not allow maintaining a constant spraying process: the welding arc was unstable, because it did not ensure constant contact of differently charged metal wires. A description of the equipment used in the experiment (including both a real prototype and a three-dimensional model) and modifications of the existing mechanism to solve the identified problem is given. Also presented a general view of the modified design, as well as a separated three-dimensional model to show the fundamental design changes. As a result, a modified model of the housing, where the welding nozzles are located, has been developed. It is capable to ensure the adjustment of the welding nozzle position and, accordingly, to guarantee constant alignment of the two intersecting metal wires.

3D SRAM Macro Design in 3D Nanofabric Process Technology

In this paper, we introduce a novel design of a 3D static random-access memory (SRAM) macro in a 3D Nanofabric process technology. The 3D Nanofabric technology is based on enabling the processing of N stack of identical layers simultaneously regardless of the number of stacked layers which consequently reduces the fabrication cost as well as the footprint of SRAM macros. To enable simultaneous patterning of stacked layers, 3D Nanofabric requires circuit topology and layout that rely on a single layer where the device channel, poly, and metal wires are all embedded without any other crossing than the gate on top of the device channel. Accordingly, we modify the layouts of the conventional SRAM bit-cell and periphery circuits which are complex and contain several metal crossings. Furthermore, we propose a new overall organization of the 3D SRAM macro that incorporates a stack of multiple identical layers each consisting of an equal size 2D array of bit-cells and the periphery circuits. We show that the proposed 3D Nanofabric SRAM macro offers 71.2% footprint gain and 36.3% read access speed improvement compared to equal size 2D SRAM macro in 3 nm FinFET.

Experimental Investigation of Wave Propagation Characteristics in Entangled Metallic Wire Materials by Acoustic Emission.

In this paper, the response characteristics of wave propagation in entangled metallic wire materials (EMWMs) are investigated by acoustic emission. The frequency, amplitude of wave emission, and the pre-compression force of the specimen can be adjusted in the experimental setup. EMWM specimens fabricated from stainless steel wires and with different design parameters are tested in this work. The results show that waves of different amplitudes propagate in EMWMs with approximate linear characteristics and the fluctuation coefficient of wave passing ratios is calculated below 15%. The response spectrum of passing waves shows a distinct single-peak characteristic, with the peak response at approximately 14 kHz. The parameters of pre-compression force, porosity, wire diameter, helix diameter, specimen height, and the layered structure of specimens have no significant effect on the frequency characteristics but moderately affect the wave passing ratios. Notably, EMWMs exhibit a lower wave passing ratio (ranging from 0.01 to 0.18) compared to aluminum alloy and natural rubber. The characteristics of response spectrums can be successfully reproduced by the finite element simulation. This work demonstrates EMWMs' potential as an acoustic frequency vibration isolation material, offering excellent performance and engineering design convenience.

Separated Liquid–Vapor Flow Analysis in a Mini-Channel with Mesh Walls in the Closed-Loop Two-Phase Wicked Thermosyphon (CLTPWT)

A metallic wire mesh screen, wire diameter of approximately 50 μm, is folded into ~80 “accordion-shaped” mini-channels and placed inside the evaporator package of a novel passive thermal management device for cooling overhead light-emitting diodes (LEDs) used in factory floors and high-bay facilities. The thermal power dissipated via these devices ranges between 75 W and 171 W. The channel walls (screen) wick liquid water from the porous wick (located centrally above the screen) and facilitate its evaporation. The closed-loop tests on this device confirm that the two-phase mixture quality exiting the evaporator is approximately 0.2. This paper presents a steady-state numerical model of this separated liquid–vapor flow in a single mini-rectangular channel (900 μm × 2000 μm, 4 cm long) with wire mesh-screen walls. The primary objective of the model is to estimate the pressure drops occurring in this two-phase flow. The model initially assumes a flat liquid–vapor interface along the channel and uses an iterative approach to estimate its final meniscus shape (curvature). In addition to the temperature distribution along the screen walls, this paper also discusses the velocity and pressure distributions in both liquid and vapor regions. It also helps understand the liquid–vapor interfacial shear in this flow configuration and proposes a flow-limiting condition for the device by predicting flow reversal in the channel.

Free and Wire-Guided Spark Discharges in Water: Pre-Breakdown Energy Losses and Generated Pressure Impulses

Impulsive underwater discharges have been investigated for many decades, yet the complex pre-breakdown processes that underpin their development are not fully understood. Higher pre-breakdown energy losses may lead to significant reduction in the magnitude and intensity of the pressure waves generated by expanding post-breakdown plasma channels. Thus, it is important to characterize these losses for different discharge types and to identify approaches to their reduction. The present paper analyses thermal pre-breakdown processes in the case of free path and wire-guided discharges in water: fast joule heating of a small volume of water at the high-voltage electrode and joule heating and the melting of the wire, respectively. The energy required for joule heating of the water and metallic wire have been obtained from thermal models, analysed and compared with the experimental pre-breakdown energy losses. Pressure impulses generated by free path and by wire-guided underwater discharges have also been investigated. It was shown that wire-guided discharges support the formation of longer plasma channels better than free path underwater discharges for the same energy available per discharge. This results in stronger pressure impulses developed by underwater wire-guided discharges. It has been shown that the pressure magnitude in the case of both discharge types is inversely proportional to the observation distance which is a characteristic of a spherical acoustic wave.

Effect of Heat Input on the Wire-Arc Additive Manufactured Steel Structures

Wire arc additive manufacturing (WAAM) is one of the less-explored metal 3D printing technologies that hold up a huge potential for large-scale product manufacturing across multiple industries. The low-cost AM uses arc energy as a heat source and metallic wire as a feedstock material. The process is sustainable and supports green manufacturing. However, the major challenge associated with the WAAM is that heat management leads to the development of residual stress causing dimensional inaccuracy and poor surface finish. Therefore, four-layer straight wall structures are fabricated by depositing material layer-upon-layer with nine distinct heat inputs (HI). The prime focus of the work is to study the effect of HI on the dimensional accuracy and the quality of deposited structures. The influence of deposition height on the surface topography is investigated. Furthermore, the effect of HI on the mechanical properties of the WAAM-printed thin wall is examined. The results show that with increase in the number of depositing layers, surface roughness values get increased under the similar process parameter used for the part fabrication. Therefore, it is recommended to re-adjust the process parameter after certain layers of deposition with proper monitoring of the thermal condition in the deposited layers while fabricating medium to large WAAM components. The outcomes from the studies show that increases in the HI while fabricating the WAAM component deteriorates the surface quality of the deposited layer and are responsible for reducing the mechanical properties of the WAAM-printed component.

Improving of Paraffin Wax Properties by Adding of Low Density Polyethylene (LDPE)

Petroleum wax is a polymer completely similar to ethylene with a high degree of crystalline and linearity. The method of mixing polymer with wax is one of the most common methods used in the field of improving the specifications of polymeric materials and making them widely used in various industrial fields. By mixing wax with different proportions of the polymer, to obtain better specifications in terms of solubility, hardness, thermal stability, and chemical resistance. Thus, it can be used in the electrical industries. This study examines some characteristics of the prepared wax such hardness, melting point, ash percentage, and electrical conductivity. The process of mixing with different percentages of wax, polyethylene and nano silver led to a clear increase in the electrical conductivity property, as the increase in the proportion of nano silver led to an increase in electrical conductivity. The polymer worked to prevent silver nanoparticles from clumping and making them cover the surface of the polymer, and thus an electrical circuit was made without metal wires.

Modeling on the size of the pre-breaking molten droplet in plasma atomization for controlling the size of the produced powders

In two-phase flow atomization, e.g., Electrode Induction Gas Atomization (EIGA) and Plasma Atomization (PA), the size of the produced powder is greatly affected by the size of the large droplet fed into the atomization zone, which is named the pre-breaking molten droplet (PbMD). In EIGA, the size of the PbMD can be quantitatively modeled as its generation from a rod by induction melting is relatively simple. While in PA, the generation of PbMD from a metal wire involves complex heat and mass transfer behavior, and there currently lacks of any quantitative model on the size of the PbMD in PA, resulting in unpredictable production of metal powders. Therefore, modeling on the size of the PbMD in PA was carried out in this study. Firstly, new phenomenological models were established to show the change in the state of the molten metal during the generation of PbMD in PA. Based on the phenomenological models, a theoretical equation for calculating the size of the PbMD with two unknown error variables was successfully deduced. Observation experiments were conducted using a high-speed camera to obtain the size of the PbMD in PA, which was used to determine the unknown error variables and verify the proposed calculation equation. The verification experiments showed that the error between the calculated and experimental results was within 10%. Moreover, it was found that the size of the PbMD in PA was much smaller than that in EIGA, which makes PA easier to produce fine powders. It was also observed that the average size of the PbMD and its variance increased with the increasing arc current of the plasma generator while decreasing with the increasing gas flow rate. With the proposed model, the size of the PbMD in PA can be predicted, and the size of the produced powders can be controlled.

Custom-made flow phantoms for quantitative ultrasound microvessel imaging

Morphologically realistic flow phantoms are essential experimental tools for quantitative ultrasound-based microvessel imaging. As new quantitative flow imaging tools are developed, the need for more complex vessel-mimicking phantoms is indisputable. In this article, we propose a method for fabricating phantoms with sub-millimeter channels consisting of branches and curvatures in various shapes and sizes suitable for quantifying vessel morphological features. We used different tissue-mimicking materials (TMMs) compatible with ultrasound imaging as the base and metal wires of different diameters (0.15–1.25 mm) to create wall-less channels. The TMMs used are silicone rubber, plastisol, conventional gelatin, and medical gelatin. Mother channels in these phantoms were made in diameters of 1.25 mm or 0.3 mm and the daughter channels in diameters 0.3 mm or 0.15 mm. Bifurcations were created by soldering wires together at branch points. Quantitative parameters were assessed, and accuracy of measurements from the ground truth were determined. Channel diameters were seen to have increased (76–270%) compared to the initial state in the power Doppler images, partly due to blood mimicking fluid pressure. Amongst the microflow phantoms made from the different TMMs, the medical gelatin phantom was selected as the best option for microflow imaging, fulfilling the objective of being easy to fabricate with high transmittance while having a speed of sound and acoustic attenuation close to human tissue. A flow velocity of 0.85 ± 0.01 mm/s, comparable to physiological flow velocity was observed in the smallest diameter phantom (medical gelatin branch) presented here. We successfully constructed more complex geometries, including tortuous and multibranch channels using the medical gelatin as the TMM. We anticipate this will create new avenues for validating quantitative ultrasound microvessel imaging techniques.

Specularly-Reflected Wave Guidance of Terahertz Plasmonic Metamaterial Based on the Metal-Wire-Woven Hole Arrays: Functional Design and Application of Transmission Spectral Dips.

Terahertz (THz) plasmonic metamaterial, based on a metal-wire-woven hole array (MWW-HA), is investigated for the distinct power depletion in the transmittance spectrum of 0.1-2 THz, including the reflected waves from metal holes and woven metal wires. Woven metal wires have four orders of power depletion, which perform sharp dips in a transmittance spectrum. However, only the first-order dip at the metal-hole-reflection band dominates specular reflection with a phase retardation of approximately π. The optical path length and metal surface conductivity are modified to study MWW-HA specular reflection. This experimental modification shows that the first order of MWW-HA power depletion is sustainable and sensitively correlated with a bending angle of the woven metal wire. Specularly reflected THz waves are successfully presented in hollow-core pipe wave guidance specified from MWW-HA pipe wall reflectivity.

Effect of oral exposure on chemical, physical, mechanical, and morphologic properties of clear orthodontic aligners

The dental industry is heavily committed to developing more esthetic solutions for orthodontic treatments. Invisalign is a system of transparent orthodontic aligners introduced as an alternative to conventional orthodontic fittings with brackets and metal wires. This study aimed to assess the chemical, physical, mechanical and morphologic changes in these polymeric aligners after exposure to the oral environment. Twenty-four Invisalign orthodontic aligners were equally divided into 2 groups: an invivo aged group in which patients used aligners for 14 days and the reference group, unexposed to the oral environment. Different experimental techniques were used to study the chemical structure, the color changes and translucency, the density and subsequent volume of the aligners, mechanical properties, surface roughness, morphology and elemental composition. The data were subjected to several statistical analyses. Clear orthodontic aligners exhibit chemical stability but undergo a statistically significant optical change in color and translucency. There was a gradual increase in the water absorption rate and the dimensional variation of the polymer, indicating a strong correlation among these factors. The mechanical properties of the polymer showed a statistically significant decrease in its elastic modulus and hardness. There was a slight tendency toward increased surface roughness of the material, but no statistical differences were found between reference and aged groups. The surface morphology of the used aligners demonstrates microcracks, distortions and biofilm formation. Intraoral aging adversely affected the physical, mechanical, and morphologic properties of the Invisalign appliance.

Synthesis mechanism and ‘orthodoxy’ test based field emission analysis of hybrid and pristine graphene nanowalls deposited on thin Kovar wires

Graphene nanowalls (GNWs) also known as carbon nanowalls (CNWs) and GNWs‑carbon nanofibers (CNFs) hybrid nanostrucrures are grown on metallic wires using a two-step microwave plasma enhanced chemical vapour deposition (MW-PECVD) process. Here, plasma is generated in two steps (first at lower pressure and then at higher operating pressure) to avoid arcing on the metallic wire during the growth. Combination of Raman and transmission electron microscopy studies revealed presence of herringbone CNFs in the hybrid nanostructures that are grown with −100 V bias compared to pristine GNWs that are grown without any bias. A new approach for field emission (FE) analysis is created by combining FN equation with ‘orthodoxy test’ in a modified approach to avoid spurious results. Here, hybrid nanostructures exhibited higher current and more repeatable field emission characteristics over 4 cycles of operation. Post FE investigations indicate that while pristine GNWs underwent many deformities and structural changes, hybrid structures remain almost unscathed. These investigations point out that a novel synthesis mechanism can be used to grow GNW based hybrid nanostructures for different applications like X-ray sources which involves FE at the core.

Microstructures and Phases in Electron Beam Additively Manufactured Ti-Al-Mo-Zr-V/CuAl9Mn2 Alloy.

Electron beam additive manufacturing from dissimilar metal wires was used to intermix 5, 10 and 15 vol.% of Ti-Al-Mo-Z-V titanium alloy with CuAl9Mn2 bronze on a stainless steel substrate. The resulting alloys were subjected to investigations into their microstructural, phase and mechanical characteristics. It was shown that different microstructures were formed in an alloy containing 5 vol.% titanium alloy, as well as others containing 10 and 15 vol.%. The first was characterized by structural components such as solid solution, eutectic intermetallic compound TiCu2Al and coarse grains of γ1-Al4Cu9. It had enhanced strength and demonstrated steady oxidation wear in sliding tests. The other two alloys also contained large flower-like Ti(Cu,Al)2 dendrites that appeared due to the thermal decomposition of γ1-Al4Cu9. This structural transformation resulted in catastrophic embrittlement of the composite and changing of wear mechanism from oxidative to abrasive.

Experimental analysis of enhanced solar still operating with induced turbulence.

This work experimentally investigates the performance of solar still with induced turbulence (SWIT) which operates with a novel approach for improved productivity. A metal wire net has been submerged in basin water of still and direct current vibration micro motor has been used to develop small intensity vibrations in wire net. These vibrations serve to induce turbulence in basin water and also break the thermal boundary layer between still surface and water to enhance the evaporation. The energy-exergy-economic-environment analysis of SWIT has been performed and compared with conventional solar still (CS) of identical size. The overall heat transfer coefficient of SWIT is found to be 66% more in comparison of CS. The SWIT provided 53% increase in yield and it is 55% more thermally efficient than CS. The average exergy efficiency of the SWIT is found to be 76% higher than that of CS. The cost of water from SWIT is 0.028 $ with a payback period of 0.74years and the carbon credit gained by SWIT is found to be 105 $. The productivity of SWIT has also been compared for intervals of 5, 10, and 15min between the induced turbulence to find suitable interval duration.

Experimental verification of magnetic near-field channeling using a helical-shaped wire medium lens

We experimentally verify that a magnetic uniaxial wire medium lens consisting of a racemic array of helical-shaped metallic wires may enable channeling the normal component of the magnetic field of near-field sources with resolution well below the diffraction limit over a broad bandwidth. It is experimentally demonstrated that the helical-shaped wire medium lens can be regarded as the magnetic counterpart of the usual wire medium lenses formed by straight metallic wires. The experimental results are validated with full-wave numerical simulations. We envision that the proposed metamaterial lens may have potential applications in magnetic resonance imaging, near-field wireless power transfer, and sensing.

Optically Transparent and Thermally Efficient 2D MoS2 Heaters Integrated with Silicon Microring Resonators

Thermal tuning of the optical refractive index in the waveguides to control light phase accumulation is essential in photonic-integrated systems and applications. In silicon photonics, microheaters are mainly realized by metal wires or highly doped silicon lines, placed at a safe distance (∼1 μm) from the waveguide to avoid considerable optical loss. However, this poses a significant limitation for heating efficiency because of the excessive free-carrier loss when a heater is brought closer to the optical path. In this work, we present a new concept of using optically transparent 2D semiconductors (e.g., MoS2) for realizing highly efficient waveguide-integrated heaters operating at telecom wavelengths. We demonstrate that a single-layer MoS2 heater with negligible optical absorption in the infrared can be placed in close proximity (only 30 nm) to the waveguide and show the best-reported power consumption of Pπ ∼ 7.5 mW for waveguide-integrated heaters (no thermal insulations) without sacrificing the optical insertion loss. The heater’s response time is ∼25 μs, which is limited by the Au/1L-MoS2 Schottky contact. Both the efficiency and response time can be further significantly improved by realizing 2D MoS2 heaters with Ohmic contacts. Our work shows clear advantages of employing 2D semiconductors for heater applications and paves the way for developing novel energy-efficient loss-less 2D heaters for on-chip photonic-integrated circuits.

High-Tolerance Thin-Film Solder Joints for Electrical Interconnection in Harsh Environments

This paper presents a pioneering use of thin-film solder joint in the electrical interconnection of high-temperature thin-film sensors, which aims to improve the low tolerance of traditional soldered balls in extreme environments. The structure of the thin-film solder joint, composed of silver foil, solder joint paste, and metal wire, has a negligible mass compared to traditional soldered balls. As a result, the inertia force on the solder joint/substrate interface during vibration and force impact is greatly reduced, improving the reliability of the solder joint under thermal-mechanical coupling impacts. The thin-film solder joint has been verified using both metal (AgPd paste) and ceramic (TiB2/SiCNO paste) solders, and can withstand extreme environments such as thermal shock and high "g" loading. The designed thin-film solder joint can withstand impact energy of up to 3 J at 1000 °C without failure, which is 6 times higher than that of traditional soldered balls (with a statistical failure rate of up to 67% under 0.5 J impact). The thin-film solder joint was successfully used for electrical interconnection of high-temperature thin-film strain gauges, demonstrating excellent reliability under thermal-mechanical coupling impacts at 1000 °C. Our high-tolerance thin-film solder joints show promising potential for use in electrical interconnection in harsh environments.

Industrial Graphene Coating of Low-Voltage Copper Wires for Power Distribution.

Copper (Cu) is the electrical conductor of choice in many categories of electrical wiring, with household and building installation being the major market of this metal. This work demonstrates the coating of Cu wires-with diameters relevant for low-voltage (LV) applications-with graphene. The chemical vapor deposition (CVD) coating process is rapid, safe, scalable, and industrially compatible. Graphene-coated Cu wires display good oxidation resistance and increased electrical conductivity (up to 1% immediately after coating and up to 3% after 24 months), allowing for wire diameter reduction and thus significant savings in wire production costs. Combined spectroscopic and diffraction analysis indicates that the conductivity increase is due to a change in Cu crystallinity induced by the coating process conditions, while electrical testing of aged wires shows that graphene plays a major role in maintaining improved electrical performances over long periods of time. Finally, graphene coating of Cu wires using an ambient-pressure roll-to-roll (R2R) CVD reactor is demonstrated. This enables the in-line production of graphene-coated metallic wires as required for industrial scale-up.