Key Engineering Materials Vol. 825

Abstract: This research proposes surface roughening of silicon wafer solar cell by electrochemical discharge machining (ECDM). The stainless steel was used as negative electrode. The graphite was used as the positive electrode acting as the auxiliary electrode. The potassium hydroxide was used as the electrolyte. The processing parameters include the machining voltage, the processing time, the machining gap, the electrolyte concentration, the additive agent concentration, pulse frequency and duty factor, etc. The result of experiments reveals that appropriate concentrations of ethanol can expand the size of the pores and enhance surface roughening effect. The appropriate processing parameters are a machining gap of 200μm, voltage of 48V, concentration of potassium hydroxide of 3M, concentration of ethanol of 4%. The electrochemical discharge machined surface roughness was increased from 0.417μm to 0.915μm using one minute processing time. The average reflectance rate of the textured surface was decreased from 29.6% to 12.7%. This study reveals that ECDM method has the advantage of short processing time and can generate a higher surface roughness and the porous structure.

Abstract: Diamond crystals are successfully synthesized by irradiating DC arc plasma jet to the substrate set in a methanol solution. It is the important procedure to preheat the substrate by inert Ar plasma jet before introducing the methanol solution gas to the plasma jet gun. The effects of two experimental conditions, the incident power and the substrates, are investigated. In the case of the Si substrate, cubic crystalline diamond grains of same size are synthesized at the plasma power of 470W. High speed hetero epitaxy is expected by using this method. In the case of the tungsten carbide substrate, diamond crystals and carbon nanotubes are simultaneously synthesized at the plasma power of 260W. The catalytic effect of Co binder in the substrate may cause the chemical reaction of the nanotube synthesis.

Abstract: A relationship between diamond synthesis and hydrogen production in in-liquid plasma method have been investigated. Approximately 60 % energy can be recovered by collecting hydrogen gas made by ingredient solution decomposition. The relationship is trade-off. When higher energy is used to maintain the substrate temperature, the hydrogen production rate gets faster, but the diamond synthesis rate gets slower. To increase diamond synthesis rate, a method should be established which maintains the substrate temperature by lower energy and generates less hydrogen gas.

Abstract: The objective of this paper is to clarify the effect of the difference of grinding fluid supply method on grinding surface characteristics during the curved surface machining of titanium alloy. The convex and concave type workpieces were machined by internal coolant supply and external coolant supply, and the surface characteristics were compared. The internal coolant supply could supply the grinding fluid directly to the machining point through the grinding wheel pores. One nozzle or seven nozzles were used for external coolant supply. As a result, the surface roughness of the concave surface decreased by about 10 % compared with the one nozzle was used when the grinding fluid was supplied from the inner side of the grinding wheel. In the case of the convex surface, the surface roughness decreased about 20 % compared with the single nozzle was used, and it decreased about 9 % compared with the seven nozzles were used.

Abstract: The objective of this paper is to clarify the effect of grinding surface characteristics in the grinding of a titanium alloy with a coolant supply from the inner side of the grinding wheel. In this paper, we selected a white aluminum oxide (WA) vitrified bonded grinding wheel and a green silicon carbide (GC) vitrified bonded grinding wheel, and compared their grinding characteristics. As a result, in the case of the GC vitrified bonded grinding wheel, the surface roughness decreased by about 54% and the compressive residual stress increased by about 128%.

Abstract: This study was performed to improve the adhesiveness of a diamond-like carbon (DLC, a-C:H) layer film with an a-SiC interlayer. In previous studies, an a-SiC/DLC layer film was formed and changes in the DLC film structure and hardness caused by the thickness of the a-SiC layer were examined. After the a-SiC interlayer thickness increased and the G-peak position shifted to a lower frequency, the peak began shifting to higher frequencies. The G-peak position reached a minimum frequency at a film thickness of approximately 0.3 μm. In contrast, as the thickness of the a-SiC interlayer increased, the FWHM of the G-peak position increased almost monotonically and the number of sp³ bonds also increased. As the interlayer thickness increased, the hydrogen content in the DLC film increased, and then began decreasing, with the interlayer film thickness exhibiting a local maximum at approximately 0.3 μm. As for the DLC film hardness, a correlation between the hydrogen content and half width of the G-peak position was observed. When the hydrogen content was ≤40 at%, a positive correlation with the FWHM (G) was observed, and when the hydrogen content was 40 at% or above, a negative correlation with FWHM (G) was found. The adhesiveness of the DLC film and substrate was improved by forming an a-SiC thin film as an interlayer. The effects of the a-SiC thin film on DLC film quality were determined.

Abstract: Cycloid planetary gear drives are widely used in power and precision motion transmission because of high gear-ratio and good shock absorbability. The aim of the paper is to propose a synthesis approach to generate necessary profiles for manufacturing with thread-wheel type tools based on a given cycloid tooth profile. Two different cases are illustrated in the paper to calculate these profiles, the profiles of thread wheel on normal or axial section, the equivalent rack profile, as well as the profile of dressing or grinding wheel for grinding or hobbing.

Abstract: With the evolution of modern science and technology, composite material is widely used in more and more fields. Its related fabrication and technology have become the important issue of development of science and engineering. Especially for fibrillar composite material, since the fiber’s orientation and distribution affect the properties of product, how the orientation and distribution are controlled is an important key to improve its properties. In this study, the external magnetic field is applied to injection molding for controlling the orientated behavior of metal fiber during the filling process. In addition, the fiber’s orientation and conductivity will be investigated by means of different process conditions (melt temperature, mold temperature, injection speed, and so on) with or without external magnetic field.

Abstract: In this study, the transition of cutting force in the tangential and radial direction during one cut was investigated in milling of AISI-1045, AISI-304, and Ti-6Al-4V with a TiN coated carbide throw-away insert. In the case of 1045 and Ti-6Al-4V, there was not obvious difference in tangential forces between up-cut and down-cut. However, up-cut showed larger radial force than down-cut in any material. In down-cut, tangential force showed almost the same regardless of radial depth of cut. 304 and Ti-6Al-4V caused larger radial force with the increase of radial depth of cut at the same cut chip thickness.

Abstract: Nowadays, Single Point Incremental Forming (SPIF) has become popular for metal sheet forming technology in industry in many advanced countries. In the recent decade, many relative studies have concentrated on this new technology of forming sheet by Finite Element Method (FEM) as well as by empirical way. There were very rare studies by pure analytical computing and P.A.F. Martins et al. under a title “Theory of single point incremental forming” performed almost all these researches were based on the analytical framework of SPIF in 2008. After careful studying on this research, we found out its light illogical result: the stresses inside of a random point in the workpiece sheet are constant and not related to the coordinate of the formed point of the sheet. Therefore, it cannot explain the mechanism of rupture and tear of the sheet that is really a serious restriction of the SPIF technology nowadays. This paper dedicates to suggest a new version of pure analytical computing the normal stresses at a random formed point in the sheet that could explain the tear mechanism and a FEM simulation was also carried out also to prove the conviction of the recommended formula.