Papers by Keyword: Surface Roughness (SR)

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Authors: Yung Kang Shen
Abstract: This paper reports a simple and novel procedure for mold insert of microlens array. The micro injection molding (MIM) and micro injection-compression molding (MICM) are used to replicate the microlens array. The 200×200 arrays of molded microlens, with a diameter of 150 $m, a pitch of 200 $m and a sag height of 11.236 $m have been successfully fabricated. The average surface roughness of the Ni mold insert is 6.916 nm. The average surface roughness of the molded microlens array is 4.608 nm for MIM and 4.555 nm for MICM. The complete fabrication process of mold insert is executed at room temperature and low pressure for this paper.
Authors: K.P. Somashekhar, N. Ramachandran, Jose Mathew
Abstract: This work is on the preparation of microelectrodes for μ-EDM operation using μ-WEDG process. Electrodes of Ø500 μm are fabricated with various discharge energy machining conditions. Effects of gap voltage, capacitance & feed rate on the surface finish of the electrodes and overcut of the thus produced micro holes are investigated. The profile of microelectrodes is measured using surface roughness tester with 2μm stylus interfaced with SURFPAK software. The study demonstrated that for brass electrodes an arithmetic average roughness value as low as 1.7μm and an overcut of 3 µm could be achieved. The significant machining parameters are found using ANOVA. Surface of the produced microelectrodes are examined using Scanning Electron Microscope. μ-WEDG process parameters could be adjusted to achieve good surface integrity on microelectrodes. Experimental results showed that the surface roughness of microelectrodes depended primarily on feed rate of the electrode. The observations showed the clear and quantitative correlation existing between the micrometer level surface quality and process parameters. The resulting microelectrodes are found to be of exceptionally high quality and could be used for μ- EDM operation on different types of work materials.
Authors: Birgit Kallinger, Bernd Thomas, Patrick Berwian, Jochen Friedrich, Gerd Trachta, Arnd Dietrich Weber
Abstract: Homoepitaxial growth on 4° off-axis substrates with different off-cut directions, i.e. [11-20] and [1-100], was investigated using a commercial CVD reactor. The characteristics of the growth process on substrates with different off-cut directions were determined with respect to applicable C/Si ratio, growth rate and n- and p-type doping range. Stable step flow growth was achieved over a broad range of C/Si ratio at growth rates ~ 15 µm/h in both cases. The n-type doping level of epilayers can be controlled at least in the range from 5  1014 cm-3 to 3  1017 cm-3 on both types of substrates. Highly p-type epilayers with p = 2  1019 cm-3 can also be grown on [1-100] off-cut substrates. Hence, the growth process for standard substrates was successfully transferred to [1-100] off-cut substrates resulting in epilayers with similar doping levels. The dislocation content of the grown epilayers was investigated by means of defect selective etching (DSE) in molten KOH. For both off-cut directions of the substrates, similar densities of threading edge dislocations (TED), threading screw dislocations (TSD) and basal plane dislocations (BPD) were found in the epilayers. Epilayers with very low BPD density can be grown on both kinds of substrates. The remaining BPDs in epilayers are inclined along the off-cut direction of the substrate. The surface morphology and roughness was investigated by atomic force microscopy (AFM). The epilayers grown on [1-100] off-cut substrates are smoother than those on standard substrates.
Authors: K.-S. Sim, Yong Sin Lee
Abstract: This paper is concerned with pressure welding, which has been known as a main bonding mechanism during the cold and warm formings such as clad extrusion or bundle extrusion/drawing. Bonding characteristics between the Cu and Al plates by pressure welding are investigated focusing on the weak bonding. Experiments are performed at the cold and warm temperatures ranging from the room temperature to 200°C. The important factors examined in this work are the welding pressure, pressure holding time, surface roughness, and temperature. A bonding map, which can identify the bonding criterion with a weak bonding strength of 1MPa , is proposed in terms of welding pressure and surface roughness for the cold and warm temperature ranges.
Authors: H. Dalai, S. Dewangan, Saurav Datta, S.K. Patel, S.S. Mahapatra
Abstract: Quality and productivity are two important aspects have become great concerns in todays competitive global market. Every manufacturing/ production unit mainly focuses on these areas in relation to the process as well as product developed. Achieving high quality necessarily requires higher degree of skill, sophisticated machine/ tools, advanced technology, precise control, immense attention-inspection and considerable time. Improvement of quality results reduction in productivity and vice versa. Thus, optimality must be maintained between quality as well as productivity. The case study highlights EDM of stainless steel in which best process environment (optimal) has been determined to satisfy productivity and quality requirements simultaneously. Material Removal Rate (MRR) during the process has been considered as productivity estimate with the aim to maximize it; whereas surface roughness i.e. (Ra value) of the machined surface has been chosen as surface quality estimate with the requirement to minimize it. These two contradicting requirements have been simultaneously satisfied by selecting an optimal process environment (optimal parameter setting). Desirability Function (DF) approach coupled with Taguchi method has been used to solve the problem.
Authors: Jian Guo Yao, Li Jie Ma, Su Fang Fu, Zhan Kui Wang, Jian Xiu Su
Abstract: In this study, according to physic-chemical characteristic of the SiC crystals, we analyzed and researched the role of pH modifier in SiC crystal substrate chemical mechanical polishing and the surface after polishing. We used different polish agents which was made up with inorganic and organic bases to experiment, and then analyzed the results. The parameters of the polishing specimen, such as the removal rate of material, surface scanning and the roughness, were analyzed and used to determine the different pH modifiers played different roles in the stability of polish agents and surface quality of the specimen.
Authors: Ashish Selokar, D.B. Goel, Ujjwal Prakash
Abstract: Abstract: Hydroturbine blades in hydroelectric power plants are subjected to erosion. Currently these blades are made of 13/4 martensitic stainless steel (ASTM grade A743). This steel suffers from several maintenance and welding related problems. Nitronic steels are being considered as an alternative to martensitic stainless steels since they have good weldability. In present work, erosive behaviour of 13/4 Martensitic and Nitrogen alloyed austenitic stainless steel (23/8N steel) has been studied. Cavitation erosion tests were carried out in distilled water at 20 KHz frequency at constant amplitude. Microstructure of eroded surface, mechanical properties and erosion rate were characterized. It was observed that 23/8N steel possesses excellent resistance to erosion in comparison to 13/4 martensitic steels. 23/8N steel showed good hardness coupled with high tensile toughness and work hardening ability, leading to improved erosion resistance.
Authors: G. Sınmazışık, D. Şen, B. Tunçelli, E. Poyrazoğlu, Burak Özkal, M. Lutfy Öveçoğlu
Authors: Jian Guang Li, Jin Guang Du, Ying Xue Yao
Abstract: This paper explains and demonstrates the machinability of dry and wet machining of SiC particle-reinforced aluminum metal matrix composites based on the experiments. The plunge surface experiments with mill-grinding method under wheel peripheral speed of up to 14.13m/s, feed rate 80mm/min and depth of cutting 50μm were carried out on a vertical CNC milling machine. The comparisons of dry and wet machining on the force composites and surface roughness (Ra) versus material removal volume were studied. The material removal volume was gained with the same machining parameters after an equal period of time. In most cases, the tangential mill-grinding force values are greater in wet machining condition than that in dry condition. But for normal mill-grinding force, the Fn values are much greater in dry machining condition than that in wet condition. And the normal mill-grinding force in wet machining increased quickly with increasing material removal volume. A better surface finish can be produced in dry machining than that produced by wet machining. The surface roughness decreased slowly with the increasing material removal volume and the surface roughness shows an insignificant decreasing trend in wet machining.
Authors: N.A.H. Jasni, Mohd Amri Lajis
Abstract: Hard milling of hardened steel has wide application in mould and die industries. However, milling induced surface finish has received little attention. An experimental investigation is conducted to comprehensively characterize the surface roughness of AISI D2 hardened steel (58-62 HRC) in end milling operation using TiAlN/AlCrN multilayer coated carbide. Surface roughness (Ra) was examined at different cutting speed (v) and radial depth of cut (dr) while the measurement was taken in feed speed, Vf and cutting speed, Vc directions. The experimental results show that the milled surface is anisotropic in nature. Surface roughness values in feed speed direction do not appear to correspond to any definite pattern in relation to cutting speed, while it increases with radial depth-of-cut within the range 0.13-0.24 µm. In cutting speed direction, surface roughness value decreases in the high speed range, while it increases in the high radial depth of cut. Radial depth of cut is the most influencing parameter in surface roughness followed by cutting speed.
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