Abstract: In this study, nanotwinned surface is fabricated on a Nickel alloy by means of a developed diamond panel with tips array. The diamond panel has an area of 10×10 mm2, and is grown using microwave chemical vapor deposition. The diamond tips are submicron in radius and formed on a silicon substrate with an array full of uniformed inverted pyramid pits. The nanotwinned surface is produced under the pressure of 1 MPa exerted by the diamond panel with tips array. Nanotwins are confirmed using transmission electron microscopy. The nanotwinned surface is generated by indention of diamond panel at room temperature using mechanical force, neither material removal nor chemical reagents. This is different from previous reports, in which high temperature, high pressure, chemical reagents or vacuum conditions are employed usually.
Abstract: KDP (KH2PO4) crystal is a kind of excellent nonlinear optical crystals, which has been widely used in nonlinear optical and Inertial Confinement Fusion (ICF) engineering. KDP crystal with the characteristics of low hardness, high brittleness, easy deliquescence and temperature-sensitive is easy to crack during the crystal growth, taken out from crystallizer, and the process of slicing. Stress concentration caused by the initial internal stress redistribution and the growth defect in KDP crystal is an important reason of KDP crystal cracking during sawing process. The numerical simulation model of the KDP crystal containing spherical cavity defect and sawing with fixed abrasive wire saw is established by finite element method in this paper. The effects of initial internal stress, spherical cavity defect on sawing stress are investigated. The maximum tensile stress near the defect during the sawing process is simulated and analyzed. The results show that sawing stress changes smoothly during sawing process, and the fixed abrasive wire saw slicing belongs to low stress cutting way. The sawing stress at sawing kerf is increased obviously. The crystal defect leads to local stress concentration during sawing process. The coupling effect of sawing stress with initial internal stress and the effect of stress concentration are enhanced when the sawing kerf approaches to the defect.
Abstract: With some conductivity and low grinding affectivity, a hybrid machining process termed electrical discharge diamond grinding (EDDG) is applied to the precision machining of reaction bonded silicon carbide (RB-SiC) ceramic. As there is electrical spark in the hybrid machining process, the electrical parameters are varied to explore their effects on the surface quality of RB-SiC ceramic with EDDG. In this paper, the experiments of different polarity and gap voltage with EEDG were investigated, and the microstructure and surface roughness on the machined surface of RB-SiC ceramic were analyzed. The surface morphology and micro-cracks were examined with a scanning electron microscope, and the surface roughness was measured with a confocal scanning laser microscope. It is found that surface roughness initially increases and then decreases with increase of the gap voltages and is higher with negative polarity than that with positive polarity. The micromorphology Micro-cracks were observed on the surface machined and are outstanding in re-solidified zone with EDDG.
Abstract: Wire sawing with diamond tools is a highly flexible cut-off grinding process with regard to machinable component structure and composition. Nowadays, it is deployed in many fields of application e.g. the dismantling of nuclear or industrial plants. Here, steel has to be cut which results in lower productivity and tool life compared to the conventional processing of natural stone. To ensure a properly designed process the mechanical and thermal tool loads have to be known in advance. This paper presents an analytical model that predicts the mechanical load as a function of the process parameters.
Abstract: The grinding of riblets with multiple profiled grinding wheels is an efficient method to minimize the fluid friction on surfaces. In turbo machinery components, like pump impellers or compressor blades, the riblets must be ground with a curved tool path since the flow is rarely linear on such surfaces. This leads to angular errors in the generated riblet profiles and therefore requires the use of grinding wheels with smaller diameters. The tool wear increases due to lateral strain on the peaks of the grinding wheel. Consequently, the increased wear and the need of smaller tool diameters decrease the efficiency of the process. In this paper a structuring process with dicing blades was investigated in order to increase the economic viability of this process. A dressing operation for such tools is not necessary and thus reduces the non-productive time of the manufacturing process. Furthermore, profile tip wear has no negative effects on the aspect ratio of the generated riblets since the riblet geometry is determined by the thickness of the dicing blades.
Abstract: With the ever-growing demand for further increase in the integration density of semiconductor devices, silicon wafers as the substrates for most devices are required to be extremely flat. In particular, it is strongly required to suppress edge roll-off, which seriously deteriorates the surface flatness near the wafer edge during polishing process in the final stage of the wafer manufacturing. In this study, we investigate the properties of polishing pads required for decreasing edge roll-off and propose the evaluation method of the properties. Polishing experiments with silicon wafers and evaluation tests for polishing pads reveal that the proposed method can estimate the obtained edge surface flatness.
Abstract: Currently, 3D printing has been attracting attention as a new method of prototyping and manufacturing. However, in the case of molding of the shell shaped resin, products by the additive manufacturing method has low strength of the interlayer adhesion and low stiffness of the light curing resin. For these reasons it is difficult to achieve the equivalent strength to injection-molded products.In study, in order to improve the strength of shell shape 3D printing, the authors propose a novel forming method by means of CFRTP and a forming system based on CAD data with local heating system, which can maintain the target formable temperature by a feedback control system was developed.
Abstract: As titanium alloys have a high strength-to-weight ratio and superior corrosion resistance, they are widely used in the aerospace, biomedical, and automotive industries. However, these alloys exhibit very poor machinability, which results in problems such as short tool life. This study investigates the effect of the cutting atmosphere on tool wear during high-speed end milling of the titanium alloy Ti6Al4V. Dry cutting, cold air jet cutting, cutting fluid mist jet cutting, and cutting fluid flush cutting were considered in order to determine the optimum cutting atmosphere and conditions. For down-cutting speeds of 200−300 m/min, the cutting atmosphere and cutting speed were adopted as experimental parameters. Down-cutting was performed in order to measure the width of the tool flank wear land as the cutting length was increased. The results indicated that the optimum cutting method was cold air jet cutting. For a cutting length of 500 mm, this method produced a narrower flank wear land than dry cutting. In addition, for longer cutting lengths of up to 4000 mm, the wear rate for cold air jet cutting was less than or equal to that for dry cutting, and no chipping or excessive wear was observed.
Abstract: Drill flute has a great influence on the drilling performance of micro-drill, and its profile largely depends on the grinding parameters, wheel profile and position. It is promising to obtain a desired flute profile with a standard wheel by adjusting the wheel position parameters. To investigate the influence of wheel position parameters on the flute profile, the micro-drill flute is simulated by MATLAB software considering the wheel installation angle and the offset distance from wheel origin to the drill blank origin, and the radial rake angle, flute width and chip evacuation capacity are quantitatively calculated to evaluate the flute profile. The simulated results show that the wheel installation angle has an obvious effect on the three performance parameters of flute profile, and the wheel offset distance only influences a parameter, i.e., the flute width evidently. The radial rake angle of drill flute increases obviously with the increased wheel installation angle, and decreases slightly with the increased wheel offset distance. With the decreased wheel installation angle, the flute width of drill flute increases causing the reduction of micro-drill strength but improvement of the chip evacuation capacity. With the increased wheel offset distance, the flute width also increases resulting in the reduction of micro-drill strength but no obvious change on chip evacuation capacity. Thus the wheel installation angle can be used as a main factor among the wheel position parameters to obtain the desired flute profile.