Advanced Materials Research Vols. 314-316

Abstract: The mechanism of the elctrochemical mechanical polishing (ECMP) technology for micro tool electrode was investigated. In this paper, suitable major process parameters on the surface quality were evaluated, the major parameters contains electrical parameters, machining gap, the working fluid and other factors. In quantitative analyses, the process of the ECMP technology were conducted. The roughness of the workpiece was reduced from a relatively high value to a mirror effect.

Abstract: The elliptical vibration cutting (EVC) technique has been found to be a promising technique for ultraprecision machining of various materials. Researchers have proved that the EVC technique prevails over both conventional cutting and 1D vibration cutting techniques in most aspects in terms of cutting performances. However, during the EVC process, vibration marks or cusps are generated by the elliptical vibration locus and can result in an increase in the overall roughness of machined surface, which is undesirable for achieving high-quality mirror surface. Although researchers have developed a calculation method for the height of the cusps, only the effects of vibration frequency on surface generation were studied, and the effects of the other vibration and machining parameters have not been investigated in detail by previous researchers. Hence, in the present study, in order to deeply understand surface generation process along nominal cutting direction under the EVC technique, which is critical for its performance improvement and application, an experimental study comprising a series of grooving tests was carried out. The effects of nominal cutting speed on the surface generation at two different thrust-directional vibration amplitudes are investigated. Analysis is given for the comparison between the theoretical and experimental roughness values, showing that there exists a critical nominal cutting speed, below which the measured roughness value is quite small and the vibration marks are almost undetectable.

Abstract: Keywords: Hydrogen, Solar, Hydrogen Production, Electrolysis, Photovoltaic Panel, Simulation Abstract. Hydrogen is regarded as the potential bearer of energy of the future. Solar hydrogen is the hydrogen produced using renewable energy, particularly solar energy [8,3]. The availability of water and hours of sunshine make Algeria a place of choice for solar hydrogen production. In this work, solar hydrogen production by electrolysis of water is considered. The required energy for water dissociation is supplied by a photovoltaic system. A design and operation study of a photovoltaic system has been done for three different regions in Algeria. The production potential is highly significant particularly in the south parts of this country.

Abstract: This thesis makes in-depth study on product assembly costs in the theoretical basis of feature mappings and cost estimation method of concurrent design. It builds up a mathematical model of feature mapping from product design domain to assemble domain, proposes a prototype system framework of assembly cost estimation and also provides theoretical and technical support for design of product cost reduction.

Abstract: The aim of this work was to improve the surface layer properties of the Mg-Al-Zn cast ZM5 magnesium alloys by melting and preplaced Al powder or Al+Y₂O₃ powder on the surface. Laser processing was carried out using high power continuous wave CO₂ laser. The resulting surface layers were examined using metallographic light microscopy, scanning electron microscopy, X-ray diffraction. The corrosion resistance was detected by potendiodynamic polarization test. The morphology of the Al cladding coatings are dendrities. And the coatings have excellent corrosion resistance compared to the untreated ZM5 substrate. The enhanced corrosion resistance coating doped with Y2O3 was attributed to the refined microstructure induced by Y₂ O₃

Abstract: The paper presents a study of renovation of aerial aluminum alloy (LY12CZ) by laser melt casting with Al matrix composite powder. The microstructure of the melt casting zone was investigated, and the fatigue contrast test was carried out between the repaired specimens and the undamaged specimens. It is found that the melt casting zone consists of equiaxed crystals and columnar crystals. The equiaxed crystals distribute in the deposited layer and the crystal size is about 3~4μm. The columnar crystals whose axial direction size comes to 30μm~40μm exist near the interface with its crystallographic axis perpendicular to the interface. The fatigue life of specimens repaired by laser melt casting was shorter than no-damage specimens to a large extant, because of the flaws in the deposited layer engendered the origins of cracks; the columnar shape grains at the bottom of casting zone were easy to split under the tensile stress; the residual stress after the melt casting accelerated the initiation and growth of the cracks.

Abstract: In order to study the dynamic response of metal of laser shock processing, dynamic strain curves of AM60 Magnesium alloy during laser shock processing were measured by resistance strain gauges. Dynamic strain curves of three equiangular rosette near the shock spot and three strain gauges of different distances from the spot center were studied. The results indicated that the strain rate of AM60 Magnesium alloy decreased and plastic deformation increased with increasing impact times. And one dimensional strain hypothesis of laser shock processing was reasonable.

Abstract: The deterioration of continuous-wave green laser-crystallized (CLC) single-grainlike polycrystalline silicon n-channel thin-film transistors (poly-Si n-TFTs) under surface channel hot-carrier (CHC) stress (VDS=16 V and VGS=16 V labeled as a CHC-1 stress) was studied. The electrical properties of trap states containing interface trap states of gate oxide and poly-Si channel and grain boundary trap states were characterized by capacitance-voltage (C-V) measurement. In addition, while a higher stress voltage, CHC-2 stress at VDS=18 V and VGS=18 V, was adopted, the increase of interface trapped charges was obviously observed.

Abstract: Experiment on ablation of silicon wafer on different crystallographic facet planes by single laser pulse irradiation was carried out with a femtosecond pulsed laser operating at a wavelength of 780 nm and a pulse width of 160 fs. The quality and morphology of the laser ablated silicon surface were evaluated by atomic force microscopy. The ablation threshold fluences on different crystallographic facet planes were obtained through the relationship between the squared diameter of the craters and pulse energy. The effects of different crystallographic facet planes of silicon wafer on the process of femtosecond laser ablation of silicon wafer were studied.

Abstract: Distortion is one type of defect in the weld, which is troublesome for some reasons, especially in thin plate welding. Distortion was found in fibre laser welding processing for 0.7mm thickness Ti6Al4V plate. The purpose of this paper is to understand and evaluate the effect of distortion on stress level by FEA and tensile test. A group of 0.7mm Ti6Al4V plates welded using continuous wave fibre laser. FEA models were established for fibre laser welded Ti6Al4V in abaqus 6.7.