Abstract: In the drilling of forging materials, exit burrs are produced on the end of hole and had some undesirable characters leading to assembly quality problem. Deburring is one of the practical techniques used to solve this problem. However, this technique is a time consuming and causes high operation cost. Hence this work presented an experimental study in drilling forging brass using special tungsten carbide drilling tools. The exit burr size was evaluated at various spindle speeds and lot size. Effect of spindle speed on exit burr height was investigated using analysis of variance (ANOVA). The results of ANOVA indicated that the spindle speed of 415 rpm gave lowest exit burr height and produced higher quantity and quality of products.
Abstract: The conventional grinding wheels employment is an economically viable alternative on Austempered ductile iron (ADI) grinding. The machining of this iron is in most cases performed with superabrasive grinding wheels, requiring machine tools with higher costs. The ADI grinding with conventional grinding wheels can produce work results comparable to the superabrasive grinding wheels, followed by lower costs and flexibility in profile grinding, since these wheels can be easily re-profiled. The aim of this work is to verify the work results of grinding ADI Grade 3 employing conventional grinding wheels. The approach is based on the influence evaluation of different abrasive microcrystalline Al2O3 percentage in these tools on the force results and roughness values in the ADI grinding. The findings show a correlation between the grinding forces and the microcrystalline abrasive percentage of microcrystalline Al2O3, since lower forces were demanded for wheels with higher percentages. Regarding the surface parameters, there was a decrease in roughness values by employing less percentages. The originality of this research is reflected in the fact that it is the first time that the influence of the composition of conventional grinding wheels is investigated on ADI Grade 3 grinding. The results present in this research will contribute to the most appropriate conventional grinding wheel specification for the ADI Grade 3 grinding.
Abstract: In this paper, the effect of addition of some grain refiners namely: molybdenum, titanium and titanium+boron to zinc-aluminum 22%, ZA22, alloy on its microstructure and mechanical characteristics is investigated in two conditions one in the cast condition and the other after pressing by the equal channel angular pressing, ECAP. Recently the ECAP process has been used to produce severe plastic deformation. It was found that addition of any of these elements to ZA22 alloy resulted in grain refinement of its structure both in the cast and after pressing by the ECAP conditions, being more pronounced after pressing by ECAP. The maximum decrease was %. Furthermore, it resulted in enhancement of its mechanical strength at, indicating softening of the alloy. Regarding the effect on its hardness, it decreased by th addition of either Mo or Ti+B. at any rate of Mo addition.
Abstract: Aluminum-Copper-Lithium alloys are used as substitute for conventional aerospace Al alloys in cryogenic tank of liquid rocket engines, aircraft wing box and satellite systems due to their high specific modulus and specific strength. For this reason they are currently under consideration for one of the potential choices for a large structure of Korea Space Launch Vehicle. In this study, friction stir welding and electron beam welding were conducted on AA2195 sheets, in butt joint configuration in order to compare the two processes and to evaluate mechanical properties. The results provide valuable information for the optimal condition of joining AA2195 sheets for a large tankage structure of the space launcher.
Abstract: Al-4% Cu alloys are now widely used in many engineering applications especially in robotic, aerospace and vibration control area. The main problem arises from the weakness of their mechanical characteristics. Therefore, this study is directed towards enhancing the mechanical properties through severe plastic deformation, hence it is anticipated that cold direct extrusion process may enhance their mechanical behavior. This was performed through using three different cross sectional dies namely; circular, square, and rectangular that have the same cross sectional area. The general microstructure, microhardness, and compression tests were performed on each specimen produced before and after extrusion for Al and Al-4% Cu alloy. It was found that the maximum enhancement in mechanical behavior was achieved after extrusion through the rectangular shape for both Al and Al-4% Cu alloy at 0.2 strain by 143% for Al and 134.8% for Al-4%Cu wt.; similarly the hardness of both of them was improved where a maximum of 141.8 % was obtained for Al-4% Cu wt. in case of rectangular cross sectional die.
Abstract: Electrospun gelatin fiber bundles were successfully prepared by self-bundling electrospinning process. A solvent mixture of 80:20 v/v acetic acid: N,N-dimethylacetamide was used as solvent for gelatin. Self-bundling was achieved by using of a grounded needle tip at the beginning of electrospinning process. Gelatin fiber bundles were fabricated from 30% w/v gelatin solutions with addition of pyridinium formate (PF) at concentrations of 3 and 5% w/v. The averaged diameters of single fiber were 452 and 410 nm, respectively; whereas, the averaged diameter of bundles were 17.2 and 22.3 μm, respectively. Viscosity and electrical conductivity of solutions were important parameters for achieving self-bundling electrospinning. Gelatin solutions with optimum electrical conductivity and viscosity could yield bundles by self-bundling electrospinning.
Abstract: The high critical current density of YBCO-coated conductors prepared by rolling assisted biaxially textured substrate technic is mostly based on the high quality cube-textured substrates. In this paper, the effect of initial grain size of ingot on the microstructure and texture evolutions during cold rolling has been investigated in high alloyed Ni8W ingots, which can affect the cube texture formation in Ni8W alloy substrates subsequently. Finally, high quality cube texture had been obtained in Ni8W alloy substrate with fine initial grain size prepared by advanced SPS technology.
Abstract: In this study, a series of poly (vinyl alcohol) (PVA)/chitosan (CS) hydrogels with different weight ratio of PVA to CS were prepared by freezing-thawing (F-T) method. The structure, morphology, and crystallinity of hydrogels were investigated by Fourier Transform Infrared (FT-IR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). FTIR demonstrated the presence of strong intermolecular hydrogen bonds between CS and PVA molecules. SEM images showed that the higher the chitosan, the greater the porous size of the hydrogel and DSC confirmed that crystallinity is higher when PVA is more in hydrogel. The mechanical properties of these hydrogels were studied by rheometry. The study of swelling ability demonstrated that the hydrogel developed with PVA and Cs was more swellable than that with PVA only because of its cross-linking interaction with PVA.
Abstract: Metal matrix composites are regarded to be one of the most predominant classifications in composites. The thermal characterization of metal matrix composites using Differential Scanning Calorimetry is a resourceful technique for the determination of heat flow distribution, specific heat capacity and enthalpy. The measurement of the thermal properties of materials is fundamental for the better understanding of the thermal design. Differential Scanning Calorimeter (DSC) is a technique that measures the difference in the heat flow to a sample and to a reference sample as a direct function of time or temperature under heating, cooling or isothermal conditions. In the present research, evaluation of specific heat capacity and enthalpy are accomplished for Al 6061, Silicon Carbide and Graphite hybrid metal matrix composites from room temperature to 300°C based on heat flow response. Based on endothermic and exothermic processes, the heat flow can be shown clearly depending on heating rate and gradual variation in temperature. The heat flow and heating rate are beneficial in the estimation of specific heat capacity for different percentage compositions of the hybrid composites.
Abstract: The reaction of polyoxovanadate and metal-Schiff base complex resulted in the formation of a new organic-inorganic hybrid compounds with the formula Na2[Mn (Salen)(H2O)2]4[V10O28]·9H2O (1) (salen=N,N’-ethylene-bis (salicylideneiminate). Compound 1 have been structurally characterized by IR, UV-vis spectroscopy and single crystal X-ray diffraction. Crystal data for 1: Triclinic, P-1, a=14.1123(3)Å, b=13.9397(7) Å, c=14.2564(5)Å, α=65.4160(9)°, β=81.3920(6)°, γ=89.5740(7) °. Structural analyses revealed that compound 1 represent a rare example of isopolyoxovanadate based metal-Schiff-base complexes, moreover, this is the first POM based metal Schiff-base complex isolated in aqueous solution medium, which may also propose a green chemical way to the synthesis of POM based hybrid. Compare with isopolyoxovanadate precusor Na6 [V10O28], compound 1 exhibit higher antimicrobial activities against human cancer cell, the phenomenon can be explained by the synergetic effect between POM and Schiff-base complex.