Papers by Keyword: Thin Wire

Abstract: solidification, process shortening and energy saving. A twin-wheel caster equipped with two additional horizontal wheels was proposed to cast thin aluminum alloy wire at higher speed. In the proposed twin-wheel caster, a groove was machined on the lower wheel. Two small horizontal wheels were positioned between the molten-metal-pouring launder and the upper wheel to assist the solidification of poured molten metal and to prevent burr formation. The alignment of the horizontal wheel sensitively affected the occurrence of wire defects. An Al-1.2%Fe wire with a cross section of 6.2 mm² was cast at 15 m/min. Thinner wires without burring could be cast at a speed higher than that of the twin-wheel caster without the horizontal wheels. The surface condition of the as-cast wire cast by the twin-wheel caster equipped with horizontal wheels was worse than that of the casting using the twin-wheel caster without horizontal wheels.

Abstract: A twin-wheel caster for casting thin aluminum alloy wire was designed, assembled, and tested. Molten metal was ejected from the nozzle (cross-sectional area: 4 mm²) of a crucible into a triangular groove that was machined on the outer surface of the lower wheel. The metal was solidified by the upper and lower wheels. Wire made of Al-1.2%Fe or 6061 aluminum alloy, whose cross-sectional area was smaller than 20 mm², could be cast at a speed of 6 or 7 m/min. The upper and lower wheels were made of copper to increase the cooling rate. The diameter of the upper and lower wheels was 200 and 600 mm, respectively. The thickness of the wheels was 10 mm.

Abstract: Dripping of polymer insulations is a different type of hazardous behaviors in wire fire, which has a potential risk of igniting adjacent combustible material and causing the dramatic growth and spread of fire in buildings, aircraft, spacecraft and nuclear power plant. To improve the fire-safety strategy, bench scale tests are conducted to study the dripping phenomenon using thin wire sample under various atmosphere pressure and electric current. The results show that the variation of flame front has a slight fluctuation during molten dripping, while the flame size (especially flame height) changes significantly. Moreover, dripping frequency (f) decreases with pressure (Ρ) due to a sufficient burning effect, but it increases with electric current (Ι) because of a stronger accumulating effect.

Abstract: Fatigue crack propagation is studied in thin wires of about 1 mm in diameter of an ultrahigh strength steel (σ_max> 2400MPa) in ambient air and in air with controlled residual humidity. A specific equipment is developed based on an electro-dynamic testing machine equipped with an environmental chamber for air humidity control. Threshold tests are run using a load shedding procedure specifically adapted to the specimen size. The relation between load ratio and crack closure is evaluated from constant K_max tests. The results are discussed on the basis of fracture surface observations and of existing modelling for environmentally assisted fatigue crack propagation.

Abstract: Recently, construction methods using gunpowder have been widely used to crush bedrock, concrete, etc. However, when these methods are used in urban areas, there can be negative safety and environmental effects. Therefore, there has been a growing demand for electric discharge shock crush, which is a static, non-blasting crush method that does not use gunpowder. This research aims to develop a method of controlling the crack direction during electric discharge shock crush. For the experiment, we used test pieces with a water-cement ratio of 55%, a height of 200 mm, and a diameter of 100 mm. Then, we created four types of wedge shape to use on the test pieces, including a two-way wedge shape, a three-way wedge shape (a downward wedge is added), a lateral disc wedge shape, and a four-way wedge shape (decahedron). For the discharge characteristics, the current and voltage waveforms had little difference between the test pieces, and it was confirmed that a larger waveform resulted from an increase in the charging voltage. Also, the two-way wedge shape could not control the crack direction. However, the three-way wedge shape could control a crack in the vertical direction and divide the test piece into two pieces. Thus, it is important to have a downward wedge (three-way wedge) to control the crack in the vertical direction. In addition, the lateral disc wedge shape generates a crack in the horizontal direction, and as a result, the test piece was sliced horizontally like a disc. Also, the four-way wedge shape cracked the test piece in the vertical and horizontal directions along the edges of the wedge. In conclusion, it was found that the wedge shape controls the crack directions.

Abstract: It is well known that the ultra grain refinement can be achieved by sever cold rolling, followed by reversion treatment in metastable austenitic stainless steel plate. In this study, the cold rolling was replaced by cold drawing. This procedure was applied to a metastable austenitic steel (Fe-16Cr-10Ni alloy) thin wire, and then the microstructure development during cold drawing and annealing was investigated. The austenite phase transformed to martensite during the drawing. Vickers hardness of the wire markedly increased with increasing the drawing strain. When the drawing strain reached about 4.5, the wire exhibited martensite single structure and had high hardness of Hv4.4GPa. Annealing of the heavily drawn wire at around 900K for 0.6ks leads to the formation of reversed austenite with the diffusional reversion mechanism. As a result, ultra fine-grained austenitic single structure with the grain size of about 0.6μm was obtained. It was also found that the wire has an excellent combination of a strength and ductility.

Abstract: A new method to investigate thin wires has been tested, which is based on a special sample holder and on a high energy X-rays. Due to the high penetration power of high energy Xrays quantitative texture data will be obtained without any additional corrections such as constant volume correction and absorption correction. The measurements have been carried out at the high energy beam line BW5 at HASYLAB – DESY (Hamburg). In order to overcome grain statistics problems on the investigated Cu-wire of 122µm thickness a special scanning routine together with the sample preparation allows to average over a wire length between 1mm and up to 240 mm.