Applied Mechanics and Materials Vols. 217-219

Abstract: This study presents a novel approach for using a micro rotary wire Electrical Discharge Machining (micro w-EDM) to thin the grinding-edge of a wheel-tool made from boron-doped polycrystalline composite diamond (PCD). For thinning the PCD, two discharge circuits (a Resistance-Capacitance (RC) circuit and a transistor) were used as power sources to obtain a grinding-edge of less than 10 µm in thickness and high surface quality. The wheel-blank is vertically mounted on a spindle and while rotating is thinned by micro w-EDM along a planned computer numerically controlled path. Experimental results verify that boron-doped PCD can be successfully thinned down to 5 µm in edge-thickness. The study shows it is possible to break (cut) diamonds of 10-µm grain size, leaving smooth surface-exposed diamonds at the cutting edge of the wheel tool. The dimensional and geometrical accuracy of the wheel-tool can be exactly controlled. Raman analysis reveals graphitizing of the PCD caused by local high temperature spark erosion at a peak of 1593 cm^-1 in RC discharge circuit machining. The peak at 1332 cm^-1 for the transistor circuit method indicates diamond sp3 structure. The surface degenerating layer produced by transistor circuit machining gives a suitably thin grinding edge with exposed diamond grains.

Abstract: This paper collects the main methodologies and tools employed for predicting the surface roughness. The goal of this work is to provide compact and adequate information that could be useful in metal cutting industries to select the techniques and optimization tools that best suit to their needs and particular requirements. Each approach, with its advantages and disadvantages, is outlined and the present and future trends are discussed. As result, a quick guide for using practitioners of mentioned industrial sector is provided in form of tables that relate: machining parameters, cutting tool properties, workpiece properties and cutting phenomena with the different techniques and optimization tools usually employed to analyze the different parameters and phenomena involved in the process of surface roughness generation.

Abstract: The robust design of chemical etching parameters is dealing with the optimization of the through-silicon via (TSV) roundness error and TSV lateral etching depth in the etching of silicon for laser drilled TSVs. The considered wet chemical etching parameters comprise the HNO₃ molarity, HF molarity, and etching time. Grey-Taguchi method is combining the orthogonal array design of experiments with Grey relational analysis (GRA), which enables the determination of the optimal combination of wet chemical etching parameters for multiple process responses. The concept of Grey relational analysis is to find a Grey relational grade, which can be used for the optimization conversion from a multiple objective case to a single objective case. Also, GRG is used to investigate the parameter effects to the overall quality targets.

Abstract: This paper presents the vibration and surface roughness issue of poly methyl methacrylate (PMMA) workpiece produced by micro end milling using integrated multi-process machine tools DT 110 (Mikrotools Inc., Singapore) with control parameter; spindle speed, feed rate, and depth of cut. The vibration was measured using accelerometer, DYTRAN Instrument and the average surface roughness Ra was measured using Wyko NT1100. The optimum solution for minimum average vibration is 64.3 Hz with spindle speed 3000 rpm, feed rate 2 mm/min, and depth of cut 1.5 μm. However, the optimum solution for minimum average surface roughness, Ra is 0.352 μm with spindle speed 2000 rpm, feed rate 2 mm/min, and depth of cut 1.5 μm. The micro end milling parameters are suitable to machine PMMA to get good precision surface roughness. The analysis revealed that the feed rate and depth of cut is the most influential parameter on vibration during machining process meanwhile for average surface roughness, Ra spindle speed is the most influential parameter.

Abstract: Abstract. Soft-contact electromagnetic continuous casting is a new technology to improve the surface quality of billet. The soft-contact electromagnetic continuous casting mold heat transfer mechanism was discussed through the molten steel heat transfer process in the mold in this paper. The aspect that previous studies have not designed in the heat transfer process has been pointed out in the last. The researchers did not add the flux film as a heat transfer medium,but the slag in the mold is a very important thermal resistance actually.

Abstract: Friction welding is a welding technique that has been studied and developed continuously. This is due to its advantages, such as it provides high quality of joint, high strength of joint. It can make welded zone through the whole section without bubble. However, there is heat generated in the welding process that can change the phase of materials. Hence, the hardness and strength of joint are affected. This paper is aimed to investigate the microstructure at the joint, which is called heat affected zone. The experiment was conducted with a number of steel rods of 10 mm. diameter. The welded specimens were tested for strength, hardness and microstructure. The temperature gradient of specimen under welding process was also recorded. It was revealed that the strength of welded element is higher but the hardness is lower. The photo of thermo scan revealed that heat is generated around the lip of interface, resulting high temperature in heat affected zone. This causes some change in microstructure composition as well as joint property.

Abstract: This article presents the results of experiments that concerned on the tool wear and tool wear mechanisms by drilling of a new Extra Low Carbon (ELC) austenitic stainless steel X02Cr16Ni10MoTiN. This article presents conclusions of machinability tests on new austenitic stainless steels X02Cr16Ni10MoTiN. The results of cutting zone evaluation under cutting conditions (cutting speed in interval vc=30-50 m/min, depth of cut ap=4.0 mm and feed f=0.02-0.08 mm per rev.).

Abstract: Chatter is defined as the self-excited violent relative dynamic motion between the cutting tool and work piece. Chatter is detrimental to all machining operations. In metal turning operations it leads to inferior surface topography, reduced productivity, and shortened tool life. Avoidance of chatter has mostly been through reliance on heuristics such as: limiting material removal rates (to stay within the dynamic stability boundary) or selecting low spindle speeds and shallow depth of cuts. However, the correct understanding of the mechanism of chatter formation in metal cutting reveals that chip morphology and segmentation play a predominant role in chatter formation during machining. Chatter is found to appear as a resonance phenomenon when the frequency of chip serration is equal to or integer multiple of the prominent natural frequency/frequencies of the system component(s). Hence, it is important to study the chip serration frequency. At lower cutting speeds the chip is often discontinuous, while it becomes serrated as the cutting speed is increased. It has been identified that the chip formation process at higher speeds also has a discrete nature, associated with the periodic shearing process of the chip. In this paper a statistical technique is proposed to predict the frequency of chip serration as a function of cutting parameters for two different tool overhang values in turning of stainless steel AISI 304 using Response Surface Methodology (RSM).

Abstract: In this paper, high quality grooves were fabricated by femtosecond laser pulse on sapphire surface. Grooves were fabricated under different experimental conditions. The lateral and vertical machining precision was evaluated by scanning electron microscopy and profilometer. High quality grooves could be obtained at the condition of low pulse energy, high scanning-speed and increasing the number of laser scans. The relationship between the width and depth of the groove and the key parameters of femtosecond laser micromachining system was studied. Several samples of the high quality grooves were obtained by femtosecond laser pulses. High quality grooves have a potential application of the fabrication of sapphire-based devices.

Abstract: To obtain complex shape alumina ceramic parts, a composite powder of epoxy resin binder E-06 and alumina powder are laser sintered combined with cold isostatic pressing(CIP). An orthogonal experiment is carried out to probe the influencing factors of selective laser sintering (SLS) alumina green parts. When preheating temperature, laser power, scan speed, scan spacing and layer thickness are, respectively, 60°C,14 w, 2000 mm/s, 0.10 mm/s and 0.10 mm, the density and bending strength of alumina parts are relatively high. Then, airproof canning prepared for CIP is manufactured in the vacuum environment. Finally, the optimized SLS/CIP alumina parts are degreased and sintered in 1600 °C to produce crack-free alumina parts. The sintered relative density of the parts however is limited to only 57% but the forming integrity during SLS and CIP remains after sintering.