Discontinuous Wires Research Articles

Fundamental research on machining performance of diamond wire sawing and diamond wire electrical discharge sawing quartz glass

In reciprocating diamond wire sawing of quartz glass, the reversing and acceleration and deceleration will cause the position change of diamond wire, resulting in the discontinuous wire sawing in the reversing stage, so as to leave residual material on the processing surface and form wire marks. Also, the cutting load will cause diamond wire deformation as bow shape, and affect the machining accuracy. In this paper, the evaluation of DWS machining performance of quartz glass focus on the sawing time, cutting force and vibration, wire tension, machining surface flatness and roughness, surface morphology and wire state. The theoretical analysis of wire mark was carried out, and the simplified wire bow model of quartz glass sawing was established. The existence of wire mark and wire bow were verified by detecting the 3D contour of the slice. In addition, a diamond wire electrical discharge sawing (DWEDS) was performed to find the differences to DWS in the above indicators. Experiments were presented in jet cooling and bath cooling conditions. It was found that the cutting force, vibration, and wire tension of DWEDS are more stable than that of DWS. The DWEDS has been proved helpful to improve machining performance of quartz glass from surface roughness, sawing time, processing state, and wire bow control as it reduces the macro cutting force acting on the diamond wire although the discharge effect is weak. The SEM of slice surface and diamond wire showed no significant difference between DWEDS and DWS. Also, the influence of feed speed and cooling methods on machining performance was investigated.

Experimental investigation of CMT discontinuous wire arc additive manufacturing of Inconel 625

Additive manufacturing (AM) is a progressive technology which holds promise for manufacturing of heat resistant super alloys. One of the most productive methods is wire arc additive manufacturing (WAAM). In this article, an alternative WAAM strategy is investigated. Experimental clads and material tests were performed to evaluate the material properties obtained through a cold metal transfer (CMT) discontinuous WAAM of Inconel 625 alloy. Using the modern terminology of Fronius Gmbh this method is called CMT cycle step. The difference is that it is automatically controlled by the welding source. CMT discontinuous WAAM has lower productivity and a higher consumption of shielding gas. However, it excels in low heat input and precise material cladding in comparison with a standard CMT continuous WAAM. It enables fabrication of finer details even on thin-walled components or in sections with problematic heat dissipation. Samples manufactured using this strategy were also compared with samples manufactured through a standard CMT continuous WAAM. Two sets of manufactured samples were thus tested. The following material tests were performed: (i) metallographic analysis, (ii) x-ray tomography, (iii) SEM analysis, (iv) hardness, (v) tensile strength (20 °C, 650 °C) and (vi) pin-on-disc (20 °C, 650 °C). The results show that the CMT discontinuous WAAM led to improved material properties in the Inconel 625 samples. Ultimate tensile strength improved by 15% at 20 °C and by 4% at 650 °C. Wear resistance at 650 °C was about two times higher. This paper concludes that the CMT discontinuous WAAM for Inconel 625 is definitely suitable for manufacturing of complex shapes, fine details and thin-walled components.

Determination of the elastic properties of randomly oriented shape memory alloy (SMA) discontinuous wires reinforced epoxy resin

A micromechanics modeling based on the equivalent fiber properties for SMA wires is developed for characterizing the elastic properties of randomly oriented SMA reinforced polymer composites using Mori-Tanaka method. The interface effect between the SMA wires and the matrix can be considered using the obtained transversely isotropic equivalent fibers. Representative volume elements (RVEs) with different shapes and sizes are employed in order to predict the elastic modulus of randomly oriented discontinuous SMA reinforced polymer composites. Experimental fiber pull-out and composite specimen tensile tests are performed in order to obtain the interfacial shear strength and validate the micromechanics results, respectively. The effect of some important parameters including aspect ratios of the wires, temperature and the pre-strain levels in the wires are investigated. The results showed that for higher aspect ratios of the wires (l/d=35) there is 20% improvement in elastic modulus of the composite in comparison with the composites reinforced by wires with lower aspect ratio (l/d=5). Moreover, pre-straining the SMA wires in martensite phase by 4%, caused 12% enhancement in the elastic modulus of the composite.

Effects of Gaps between Discontinuous Wire Woven Kagome Cores upon Bending of Sandwich Panels

WBK (Wire-woven Bulk Kagome) is a periodic cellular metal assembled of helical wires. The mechanical behavior under compression or shear, optimal design of a sandwich panel with WBK core, and characteristics of heat dissipation media have been studied, which proves feasibility of WBK as core material with multi-function capability. When WBK is used as the core material in a large scale sandwich panel, gaps between discontinuous cores are inevitable in their fabrication or building even larger scale structures using them. In this study, the effects of the gaps on mechanical behavior of sandwich panels are investigated. Theoretic analysis, experiments with three-point bending, and numerical analyses are performed to predict the strength and to analyze the results

Principles and applications of a controllable electromagnetic band gap material to a conformable spherical radome

This paper presents the principle of two types of conformable and controllable spherical radome based on Electromagnetic Band Gap (EBG) materials operating at around 10 GHz. The EBG structure is composed of a grid of metallic wires conformed on a hollow spherical object. Two switching control configurations are considered: (1) between an EBG structure made of electrically continuous wires and another one made of discontinuous wires, and (2) between two EBG structures made of discontinuous wires where each has a different period of discontinuities. Both switching configurations are simulated and experimentally characterized on passive prototypes. An excellent agreement is observed between simulations and measurements. The radiation patterns of two types of antennas, a horn antenna and a meteorological antenna, are also measured in the presence of the radome.

Technique for Reducing the Power Supply in Reconfigurable Cylindrical Electromagnetic Bandgap Structures

In this letter, a new design of cylindrical electromagnetic bandgap (CEBG) structures is proposed in order to reduce the power supply used to control active elements in EBG-based reconfigurable antennas. The proposed configuration uses structures of discontinuous wires with defects consisting of continuous wires. To examine its performances, numerical simulations were carried out using a finite-difference time-domain (FDTD) code, for the structure without active elements. The obtained results show that the new configuration allows to obtain a directive beam in the pass-band of the all continuous-wires structure. This work has potential application for designing an antenna with a directive pattern able to turn over 360deg range

Simultaneous deposition of Ni nanoparticles and wires on a tubular halloysite template: A novel metallized ceramic microstructure

Tubular halloysite can be used as a template to fabricate a novel metallized ceramic microstructure through electroless plating. Reduction of Pd ions by methanol is conducted to initiate Ni plating. There is a simultaneous deposition of Ni nanoparticles on the outer surface and discontinuous wires in the lumen site of the halloysite template obtained. The different deposition could be caused by the different composition distribution of ferric oxide impurity in the wall due to the isomorphic substitution during the formation of halloysite template. Its magnetic property is mainly attributed to the Ni nanoparticles, not the wires. The metallized ceramic microstructure has the potential to be utilized as a novel magnetic material.

Self-aligned Split Gate Electrodes Fabricated on Suspended Carbon Nanotubes

ABSTRACTWe describe the fabrication of self-aligned split gate electrodes on suspended multiwalled carbon nanotube structures. A suspended multiwalled carbon nanotube structure was used as an evaporation mask for the deposition of metal electrodes resulting in the formation of discontinuous wire deposition. The metal deposits on the nanotubes are removed with lift-off due to the poor adhesion of metal to the nanotube surface. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gaped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems.

Self-aligned Split Gate Electrodes Fabricated on Suspended Carbon Nanotubes

ABSTRACTWe describe the fabrication of self-aligned split gate electrodes on suspended multiwalled carbon nanotube structures. A suspended multiwalled carbon nanotube structure was used as an evaporation mask for the deposition of metal electrodes resulting in the formation of discontinuous wire deposition. The metal deposits on the nanotubes are removed with lift-off due to the poor adhesion of metal to the nanotube surface. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gaped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems.

Fabrication and mechanical properties of steel–steel composites

Metal matrix composites based on a low carbon steel matrix reinforced with high carbon steel wires have been fabricated by a combined cold and hot rolling process. Both continuously and discontinuously aligned composites have been produced. A subsequent heat treatment allowed the formation of martenisitc, bainitic or pearlitic wires in a ferrite predominantly matrix. The optimum wire microstructure giving a composite with high strength and reasonable ductility was found to be bainitic — martensitic wires were found to contain microcracks that gave poor composite strengths and ductilities. The discontinuous wire composites produced similar strengths to the continuous composites only when they were deformed to give a wire aspect ratio greater than 20. The strengths of both types of composites showed a good fit to the rule of mixtures as the volume fraction of fibers was increased.

Active metallic photonic band-gap materials (MPBG): experimental results on beam shaper

We focus our attention on the possibilities to control the beam radiated by antennas, which are initially omnidirectional using active metallic photonic band-gap materials (AMPBG). In fact, MPBG composed of continuous or discontinuous wires present different and interesting characteristics when they are used as an antenna reflector or a radome. Adding active components on wires allows one to switch from continuous to discontinuous structures. Wires with active elements on can then be placed inside a structure, which shapes the beam radiated by a dipole antenna. Experimental results show that it allows one to switch on/off the beam or to change its shape.

Tensile properties of fibre reinforced metals—II. Creep of silver-tungsten

Measurements of the strain-time curve have been made on silver specimens containing 40 per cent by volume of aligned tungsten wires at temperatures between 400°C and 600°C. The wires greatly reduce the rate of creep of the matrix. The rate of creep of composites containing discontinuous wires appears to be governed by the rate of creep of the matrix under the action of the shear stresses which arise close to the fibre-matrix interface.

Tensile properties of fibre-reinforced metals: Copper/tungsten and copper/molybdenum

T ensile tests at a variety of temperatures have been carried out on composites consisting of tungsten or molybdenum wires, uniaxially aligned in a copper matrix. Both continuous and discontinuous wires have been used, and both brittle and ductile tungsten wires. It is found that the breaking strength is a linear function of the wire content. A simple theory to explain this is developed and auxiliary experiments to check the theory are described. Some simple predictions about the behaviour of fibre reinforced metals are made from the results.