Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jmapro.2023.10.039

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Laser Institute of America  

This study investigated the effects of laser beam intensity distribution on the reduction of dross height in fiber laser cutting of a steel plate with 3.2 mm thickness. A twin-spot beam was produced by splitting a single Gaussian beam into two beams using a special axicon lens, and these beams were set in the scanning direction for cutting experiments. The power ratio of two beams (R:F = Rear power:Front power) was varied to discuss the intensity balance for the effective reduction of dross. After cutting experiments, ray tracing analysis was conducted using an optical analysis to calculate the absorbed power density distributions in the kerf. A smaller dross height of 18 μm can be achieved at a power ratio of R:F = 8:2, and its value is lower than that by a single Gaussian beam. At a power ratio of R:F = 8:2, the front beam of lower power is irradiated at the upper part of the workpiece, and the rear beam of higher power is absorbed at the lower part of the workpiece. Thus, effective heat input to the lower part of the workpiece can contribute to a reduction of the dross height. Variation of power ratio in the rear and the front beams is effective in controlling the cutting front shape, and the uniformity of absorbed power in the thickness direction can be improved by setting the rear beam of about four times higher power to the front beam of lower power to obtain a smaller dross height in the case of a 3.2 mm steel plate.

DOI： 10.2351/7.0001097

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Laser Institute of America  

In order to achieve sustainable development goals, decarbonization and low-carbonization are required. Electric and hybrid vehicles are indispensable for the conservation of natural environment, and the lightweight construction and the effective transfer of electricity become important. Thus, copper and aluminum have been increasingly recognized as important materials because of their excellent materials’ properties. However, in the welding of these materials, it is difficult to obtain strong joints because there are problems in the brittle intermetallic compounds and the welding defects due to different melting points between copper and aluminum. Especially in the joining of copper and aluminum by copper side irradiation, aluminum-rich intermetallic compounds (IMCs) of brittle state result in the decrease of mechanical strength. Therefore, mild heat input from copper to aluminum would be necessary to reduce the brittle IMC. Angled irradiation might result in the mild energy input to aluminum because it can be expected that aluminum would be heated by the reflected light inside the keyhole generated in copper according to its high light reflection. In addition, stable welding can be expected by the superposed irradiation of blue and near-infrared lasers because of high light absorption rate of blue laser to copper. The angled and the superposed irradiation could achieve a stable welding state, and the generation of aluminum-rich IMC becomes smaller. Angled irradiation of a near-infrared laser showed equivalent joining strength to the superposed irradiation of two wavelengths, and the combination of angled and superposed irradiation achieved a remarkable increase of joining strength in a cross tensile test by 80%.

DOI： 10.2351/7.0001096

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Additively manufactured (AMed) titanium products are typically produced by electron beam melting (EBM), since oxidation of titanium alloy surface can be suppressed in vacuum environment. The surface roughness of AMed titanium products becomes more than 200 µm Rz, and the very rough surface would lead to reduction in fatigue strength. Therefore, a post surface finishing process is required. Abrasive blasting is one of the common surface smoothing processes of AMed metal products. Large surface roughness can be decreased, and compressive residual stress can be introduced to the surface. However, there is a limitation to reduction of surface roughness to several µm Rz. On the other hand, it was recently found that AMed metal surface produced by powder bed fusion with laser beam could be smoothed by large-area electron beam (LEB) irradiation. However, it is difficult to smooth surface with large initial surface roughness, and a tensile residual stress may be generated on the surface. In this study, surface smoothing and change in residual stress of AMed titanium alloy (Ti-6Al-4 V) were proposed by combination of grit blasting and LEB irradiation. Surface roughness of AMed Ti-6Al-4 V alloy significantly decreases from 265 to about 2.0 µm Rz by combination of grit blasting and LEB irradiation. Reduction rate of surface roughness by LEB irradiation linearly increases with decreasing mean width of blasted surface. Influence of the mean width on smoothing effect by LEB irradiation can be explained by thermo-fluid analysis. Moreover, tensile residual stress caused by LEB irradiation can be reduced when LEB is irradiated to blasted surface.

DOI： 10.1007/s00170-023-11857-5

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Other Link： https://link.springer.com/article/10.1007/s00170-023-11857-5/fulltext.html

Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Titanium alloy Ti6Al4V has been widely applied to medical, automotive, and aerospace industries due to its excellent properties such as high strength and excellent corrosion resistance. On the other hand, additive manufacturing (AM) technology can give the freedom of design of the products. In order to spread the AMed products, the joining of AMed and wrought products are required, and it is important to understand the joint characteristics. In this study, butt welding of Ti6Al4V plate was conducted by fiber laser in argon shielding, and the joint characteristics of laser weld wrought/wrought, AMed/AMed, and AMed/wrought Ti6Al4V plates were experimentally investigated. The AMed plate has higher tensile strength than wrought plate but the elongation of AMed plate is smaller, since AMed plate has α’ martensite due to rapid cooling during laser irradiation in AM process. Then, the laser weld joint of AMed/AMed plates has higher tensile strength, but smaller elongation than that of wrought/wrought plates. The weld joint of AMed/wrought plates shows good welding state, since small heat input leads to formation of small weld bead with higher hardness between wrought and AMed plates.

DOI： 10.1007/s40194-023-01533-3

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Other Link： https://link.springer.com/article/10.1007/s40194-023-01533-3/fulltext.html

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jmatprotec.2023.117866

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jmatprotec.2022.117813

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier BV  

DOI： 10.1016/j.procir.2022.09.152

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DOI： 10.1016/j.procir.2022.09.153

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier BV  

DOI： 10.1016/j.procir.2022.09.123

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DOI： 10.1016/j.procir.2022.09.184

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier BV  

DOI： 10.1016/j.procir.2022.09.109

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DOI： 10.2351/7.0000740

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

<title>Abstract</title>
The flat plane of small surface roughness below 0.1 µm average roughness could be obtained for monocrystalline diamond by nanosecond pulsed laser irradiation of 1060 nm and post-process of acid cleaning, at the laser fluence around the threshold value of material removal. The glossy and flat plane at the bottom of micro-groove was parallel to the top surface of specimen, although the round beam of Gaussian-mode was irradiated in the direction perpendicular to the top surface of specimen. The square beam of top-hat mode could obtain shallower micro-groove with wide flat bottom in comparison with the round beam of Gaussian mode, and then the creation method of flat plane with small surface roughness was discussed in the arrangement strategy of linear micro-grooving by the square beam of top-hat mode. Normal side-by-side repetition of linear micro-grooving could not create the flat plane of a constant depth. Therefore, two-step scanning method was proposed in order to overcome the problem in the normal side-by-side repetition of liner micro-grooving. Non-removal areas were partly retained between the processing lines in the first step, and the laser scanning was conducted on the retained area in the second step. Newly proposed two-step scanning method was practical and useful to create a wide flat plane with small surface roughness, and the controllability of micro-groove depth could be improved by the two-step scanning method. This proposed method can reduce the surface roughness in addition to the shape creation of monocrystalline diamond, and it can be used as the high-quality micro-shape fabrication method of monocrystalline diamond.

DOI： 10.1088/2631-7990/ac5a6a

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Other Link： https://iopscience.iop.org/article/10.1088/2631-7990/ac5a6a/pdf

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Electrical Machining Engineers  

DOI： 10.2526/ijem.27.22

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jmatprotec.2021.117388

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Laser Institute of America  

DOI： 10.2351/7.0000470

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Laser Processing Society  

DOI： 10.2961/jlmn.2021.02.2006

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications  

This study investigated the effect of boron-doped and undoped diamond coatings on the cutting performance of cobalt cemented tungsten carbide (WC-Co) drills when drilling CFRP. Three types of diamond coating, as boron-doped microcrystalline (B-MCD), boron-doped nanocrystalline (B-NCD), and undoped nanocrystalline (NCD), were deposited on specially designed for drilling of CFRP one-shot drills by the hot filament chemical vapor deposition (HFCVD) method. The coating characteristics, such as surface morphology, roughness, carbon structure, and interfacial adhesion, were investigated. Then cutting tests were carried out, and the tool’s flank wear, thrust force, and torque were evaluated. For comparison of cutting performance, non-coated WC-Co drills were used in the tests as well. Furthermore, drilled holes were inspected in terms of peel-up and push-out delamination. According to the results, the B-MCD coated drill presented advantages in tool life, and quality of drilled holes over the NCD and B-NCD coated drills. Also, the results confirmed the adhesion enhanced effect of diamond coating to WC-Co substrate through boron doping of the layer.

DOI： 10.1177/09544054211040624

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Other Link： http://journals.sagepub.com/doi/full-xml/10.1177/09544054211040624

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

DOI： 10.1117/12.2584895

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Electrical Machining Engineers  

DOI： 10.2526/ijem.26.54

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier BV  

DOI： 10.1016/j.procir.2020.02.280

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DOI： 10.1016/j.procir.2020.02.282

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DOI： 10.1016/j.procir.2020.02.283

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J-GLOBAL

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

With recent improvements in adhesive performance, adhesive joints are being increasingly used in various industrial fields. Despite their advantage of joining dissimilar adherends, adhesive joints are considered unsuitable for key components of mechanical structures due to their large variation in joint strengths. There are many factors that affect the strength of adhesive joints. However, the general bonding mechanisms are (1) mechanical, (2) physical, and (3) chemical bonding. The adhesion mechanism is complex because these phenomena occur simultaneously. Thus, it is necessary to consider these factors separately. Moreover, it is important to understand the bonding mechanism of interfaces in adhesive joints and to improve the reliability of the joint strength. In this study, the tensile strengths of single lap joints were measured to investigate the influence of large-area EB irradiation on strength characterization of adhesive joints. Aluminum alloy plates (A6061) were used as the adherend. Other surface treatments, which were sanding by emery paper, shot blast, and plasma irradiation, were also conducted for comparisons. Each treated surface of the adhered was examined with respect to the surface profile, wettability, and surface analysis by XPS. Results showed that the wettability of treated surfaces of adherend improved, and tensile strength of surface treated adhesive joints was also improved compared with that of the non-treated specimen. Specifically, the strength of the joint with EB irradiation was 1.9 times larger than that of the non-treated specimen. Finally, the effect of large-area EB irradiation on adhesive characterization was discussed.

DOI： 10.1299/jamdsm.2021jamdsm0052

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Authorship：Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/transjsme.20-00205

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/transjsme.20-00213

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J-GLOBAL

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/transjsme.20-00213

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Precision Engineering  

DOI： 10.2493/jjspe.85.359

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Electrical Machining Engineers  

DOI： 10.2526/ijem.24.21

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In micro machining of monocrystalline diamond by pulsed laser, unique processing characteristics appeared only under a few ten picosecond pulse duration and a certain overlap rate of laser shot. Cracks mostly propagate in parallel direction to top surface of workpiece, although the laser beam axis is perpendicular to the surface. This processed area can keep diamond structure, and its surface roughness is smaller than R-a = 0.2 mu M. New laser micro machining method to keep diamond structure and small surface roughness is proposed. This method can contribute to reduce the polishing process in micro machining of diamond. (C) 2019 Published by Elsevier Ltd on behalf of CIRP.

DOI： 10.1016/j.cirp.2019.04.119

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J-GLOBAL

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

In large-area electron beam (EB) irradiation method developed recently, high energy density EB can be obtained without focusing the beam. Therefore, large-area EB of 60 mm in diameter can be used for instant melting and evaporation of the wide area material surface, and high efficient surface finishing is possible. However, if the workpiece has a hole shape, the EB concentrates in the entrance edge or inside wall of the hole. Thus, it is difficult to smooth the hole bottom surface. Previous study showed that the surface smoothing and micro-deburring effects for non-magnetic workpiece could be improved by setting a magnetic block under the workpiece, since the electrons tend to concentrate the magnetic block along magnetic lines. In this study, smoothing of hole bottom surface was experimentally investigated by setting a magnetic block under a workpiece in large-area EB irradiation. Expansion of smoothing area of the bottom surface was also tried by setting a through hole at the center of the magnetic block. It was clarified that wide area of hole bottom surface could be smoothed by large- area EB irradiation by setting the magnetic block under workpiece. The surface roughness decreased to less than 3.0 μmRz at the area of hole bottom surface. When the hole diameter was 20 mm and hole depth was less than 40 mm, smoothing area of 10 mm in diameter was obtained by using the magnetic block. Moreover, the smoothing area was sufficiently expanded by setting a through hole with an appropriate diameter in magnetic block.

DOI： 10.1016/j.jmatprotec.2017.11.024

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

In large-area electron beam (EB) irradiation method developed recently, high energy density of EB can be obtained without focusing the beam. Therefore, the wide area of material surface can be melted instantly, and high efficient surface finishing is possible. Moreover, surface functions such as corrosion resistance and water repellency of the metal molds were improved by the large-area EB irradiation, since thin resolidified layer was formed on the metal surface. It is expected that thick modified layer is effective to maintain their surface functions for long-term. Therefore, control and prediction of the modified layer thickness are important in order to obtain appropriate modified layer thickness on metals with different material properties. In this study, variations of modified layer thickness on metals with different material property are experimentally investigated. Furthermore, electron behavior during large-area EB irradiation is simulated by using an electron track analysis, and prediction of the modified layer thickness is tried with temperature distributions by using an unsteady heat conduction analysis. Experimental results show that the modified layer thickness increases with increasing energy density. The thickness with high relative permeability is larger than that with low one. Analytical results of the modified layer thickness in unsteady heat conduction analysis show quantitative agreement with experimental ones. Furthermore, the modified layer thickness on the metals with different thermal property and density is also discussed. Then, the modified layer thickness of metals with different material property can be predicted by using our unsteady heat conduction analysis model. (C) 2018 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.procir.2017.12.043

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Fuji Technology Press  

In recent years, one common cure for losses in joint function caused by osteoarthritis or rheumatoid arthritis is replacement with an artificial joint. For this reason, it is necessary to add osteoconductivity to artificial joint component surfaces that make contact with bone, thereby reducing the period of time necessary to fixate the bone tissue and the artificial joint component. With the intent of efficiently machining the joint shape by electrical discharge machining (EDM) and simultaneously formation of a surface with osteoconductivity, this study discusses the possibility of adding osteoconductivity to a titanium EDMed surface.

DOI： 10.20965/ijat.2017.p0869

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In laser processing of silver nanowire transparent conductive film covered with an acrylic resin layer, effects of pulse duration on electrical insulation and surface quality were experimentally investigated by using nanosecond pulsed laser. The minimum laser fluence to achieve the stable electrical insulation by removal of silver nanowire became small with decreasing the pulse duration, but shorter pulse duration showed drastic change of removal trace area of silver nanowires at the boundary region of laser fluence to change conductive state to insulation one. In contrast, longer pulse duration around 200 ns indicated almost constant small removal trace area of silver nanowires, and wide processing window to perform the stable electrical insulation with small removal trace area of silver nanowires can be expected by using a proper long pulse duration in nanosecond pulsed laser processing. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2016.10.004

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Small-diameter curved hole EDM drilling method using a metal ball electrode suspended with flexible thin foil has been studied using zinc alloy with low melting point as workpiece material. In order to improve the drilling performance and to extend drillable hole depth for practical materials, such as aluminium alloy and steel, curved hole drilling with workpiece vibration was proposed in this study. The influences of discharge conditions and vibration amplitude on the machining characteristics were experimentally investigated. Various types of curved holes were successfully drilled in practical materials by EDM using the suspended ball electrode with workpiece vibration. (C) 2017 Published by Elsevier Ltd on behalf of CIRP.

DOI： 10.1016/j.cirp.2017.04.125

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

In large-Area electron beam (EB) irradiation method, uniformly high energy density can be obtained without focusing the beam. Large-Area EB can be used for melting and evaporating metal surface instantly. It was clarified that high efficient surface finishing of metal mold steels, ceramics and cemented carbides was possible by the large-Area EB irradiation. Furthermore, the tip of convex shape was often rounded after large-Area EB irradiation with remarkable material removal at the tip. This phenomenon is probably caused due to the heat accumulation and electrons concentration at the tip. However, electrons behavior near the workpiece surface during large-Area EB irradiation has not yet been clarified. In this study, electron track analysis was conducted in order to clarify electrons behavior during large-Area EB irradiation. At first, analytical model of the large-Area EB irradiation apparatus was built. Then, the EB diameter on the workpiece surface was experimentally measured with different energy density in order to evaluate the accuracy of our analytical model. The calculated results of EB diameter were in good agreement with the experimental ones. In addition, the electrons concentration phenomenon at the tip of convex shape was clarified by calculating energy density distribution on the surface obtained with electron track analysis. The analytical results indicated that the energy density increased from edge to tip of convex shape, while the energy density was constant in the case of planar shape. Experimented results also showed that removal thickness increases with high relative permeability. These results were similar tendency to the energy density distribution. Therefore, electrons concentration on the tip could be simulated by the electron track analysis.

DOI： 10.4028/www.scientific.net/KEM.749.118

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

In wire EDM (electrical discharge machining) process, it is important to smoothly exclude debris and bubbles generated in the working gap for keeping stable performance. Much debris stagnation in the gap would cause frequent occurrence of discharge concentration and secondary discharge, which results in unstable machining performance, such as frequent wire breakage, low removal rate, and low shape accuracy. Therefore, a jet flushing of working fluid using upper and lower jet nozzles has been conventionally applied for excluding the debris and bubbles from the machined kerf. Nevertheless, it is well known that the wire often breaks when the machined kerf length is a few mm from the start hole in 1st-cut wire EDM. The influence of machined kerf length on the flow field, the debris exclusion, and the wire behavior caused with hydrodynamic force by the jet flushing should be made clear. In this study, variations of flow field in the kerf, the debris accumulation state and the wire deflection caused jet flushing with machined length were analytically investigated by CFD (computational fluid dynamics) and structural analysis when 1st-cut wire EDM was done from a small start hole. Moreover, the effects of machined kerf length on the wire deflection and wire breakage were discussed. Wire breakage frequency experiments showed that wire tended to frequently break at a certain machined kerf length, where the wire deflection rapidly increased and the debris residence time in the gap became long.

DOI： 10.4028/www.scientific.net/KEM.749.130

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Fuji Technology Press  

In laser cutting and drilling process, molten material was scattered as spatter, which deteriorates the surface integrity of a workpiece because of the thermal damage. It is expected that the control of assist gas flow can reduce the adhesion of spatter. In order to investigate the improvement method of thermal damage due to the adhesion of spatter, it is required to clarify characteristics of spatter. Therefore, a method was developed to collect and analyze spatter based on the use of high-speed video cameras in the lasermicro-drilling process, and the characteristics of spatter movement were numerically investigated by CFD analysis. The scattering velocity and angle of the spatter were investigated by recognizing and tracking spatter with the high-speed video observation. The movement of spatter was observed by using two high-speed video cameras, and analyzed by using a two-direction tracking method, in which the 3D tracking lines of spatter particles were reconstructed in the forward and backward frames, and the actual trajectory of individual spatter particle was obtained by averaging those tracking lines. These measurements revealed that the initial velocity of spatter was mainly distributed from 52 m/s to 200 m/s with an average velocity of 129 m/s. The initial angle of spatter was mainly distributed between 0 and 30 degrees from the workpiece surface in the upward direction. There was little correlation between the initial velocity and angle of spatter. The diameter of spatter was mainly distributed from 1 µm to 4 µm with an average diameter of 3.7 µm. It is important to use the processing conditions achieving the smaller spatter diameter in order to reduce the thermal damage caused by spatter. Although coaxial assist gas flow has an influence on the spatter behavior, that time period is very short. Therefore, it is important to control the spatter behavior outside of the coaxial assist gas flow by using an additional gas flow to prevent the thermal damage to the workpiece surface.

DOI： 10.20965/ijat.2016.p0874

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

In large-area electron beam (EB) irradiation method, corner tip of workpiece is generally rounded since removal of material at the tip is done preferentially. Investigation of the shape change is necessary to clarify rounding phenomenon with irradiation of EB. In this study, the shape changes of corner tips were experimentally investigated by Scanning Electron Microscope (SEM) observation of the cross sections. Then, electron track analysis in the EB irradiation was conducted to clarify an electron concentration at the tip. Unsteady heat conduction analysis at the tip was also done with considering the EB concentration at the tip and an electron penetration effect into the surface. The shape changes were estimated by simulation of temperature distribution at the tips. Experimental results show that the curvature radius increases with shot number of EB. The estimated shape changes show quantitatively good agreement with the experimental ones. These results indicate that the rounding phenomenon at the tips by large area EB irradiation can be predicted by our electron track and unsteady heat conduction analysis model. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijmachtools.2016.08.002

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The characteristics of the molten area are attributed not only by laser energy condition but also the focusing condition. In this study, a picosecond pulsed laser of 1064 nm in wavelength and 12.5 ps in pulse duration was used as a laser source for joining glass material. Influence of focusing condition on micro-welding of glasses was experimentally investigated by using an objective lens with and without spherical aberration correction, and its molten area was characterized. The usage of objective lens with spherical aberration correction led to a larger molten area inside the bulk material of glass even under the same pulse energy, which related to the efficient micro-welding of glass materials. In addition, an optical system with the spherical aberration correction led to a stable absorption of laser energy inside the bulk glass material, stabilizing the shape of molten area, which resulted in the reliable weld joint. On the other hand, breaking strength of the specimens with spherical aberration correction was higher than that without spherical aberration correction. Therefore, it is concluded that the focusing condition with spherical aberration correction led to the larger and stable molten area, which resulted in higher joining strength in micro-welding of glass materials.

DOI： 10.1007/s00339-016-0026-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IGI Global  

In the present study, a three-dimensional finite element model has been developed to simulate the temperature, stress and deformation fields in continuous wave (CW) laser micro-welding of thin stainless steel sheet. The welding deformation was experimentally evaluated using a single-mode fiber laser with a high-speed scanning system. Application of developed thermal model demonstrated that the laser parameters, such as laser power, scanning velocity and spot diameter have a significant effect on temperature field and the weld pool. In the case of welding deformation, numerical simulation was carried out by an uncoupled thermo-mechanical model. The welding stress and deformation are generated by plastic deformation during the heating and cooling periods. It was confirmed that the residual stress is higher than yield strength and has strongest effect upon the welding deformation. The numerical simulated results have proved that the developed finite element model is effective to predict thermal histories, thermally induced stresses and welding deformations in the thin material.

DOI： 10.4018/IJMMME.2016040104

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Micro-welding characteristics of silicon and glass by pulsed lasers are described. In this study, four types of laser beam, which are nanosecond pulsed laser and picosecond pulsed laser of 532 and 1064 nm in wavelength, were used for joining monocrystalline silicon and glass. Influence of wavelength and pulse duration on micro-welding of monocrystalline silicon and glass was experimentally investigated under the same spot diameter, and the molten area of monocrystalline silicon and glass was characterized. Finally, the breaking strength was evaluated for the overlap weld joint with different pulse duration and wavelength. A splash area of molten silicon around the weld bead line was obvious in the nanosecond pulsed laser. On the other hand, there was no remarkable molten splash around the weld bead line in the picosecond pulsed laser. Breaking strength of specimens with 1064 nm wavelength was higher than with 532 nm wavelength in nanosecond laser, whereas breaking strength of laser-irradiated specimen by picosecond pulse duration was higher than that by nanosecond pulse duration. It is concluded that the combination of picosecond pulse duration and infrared wavelength leads to the stable molten area appearance of the weld bead and higher breaking strength in microwelding of glass and monocrystalline silicon.

DOI： 10.1007/s00339-016-9849-5

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Wire movements and vibrations are one of the most important phenomena of wire electrical discharge machining (EDM) process. Unstable wire electrode behavior and large wire vibration amplitude during the process cause wire breakage, low shape accuracy and large machined surface roughness. In this study, direct observation using high-speed camera investigated the movements of tungsten wire electrode during fine wire EDM process. The results showed that the vibration amplitude and frequency depended mainly on the wire tension, and the amplitude direction. The amplitude in the direction parallel to the machining direction was a little larger than that in the perpendicular one. In addition, the backward deflection of wire could be confirmed even in fine wire EDM. Also, the wire vibration mode was analyzed, and it could be varied with the machining position of the thin workpiece, which possibly led to smaller wire amplitude. Furthermore the amplitude envelope of wire electrode during the process was clarified. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2015.08.015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

Today the use of high-strength carbon fiber-reinforced plastics (CFRP) composite as a material for many engineering applications is showing an increasing demand in the industry. These composites are replacing the traditional use of steel because they offer many advantages such as very light weight, high strength, and high stiffness associated with good corrosion-resistant properties. Unfortunately, there is little technological knowledge on the electrical discharge machining (EDM) process of high-strength composite materials, especially about the CFRP. In this work, a study has made into the possibility of using EDM process as a means of machining CFRP composite. Various cutting conditions such as peak current, pulse-on time, pulse-off time and open-circuit voltage were selected to perform electrical discharge machining. The effect of electrode rotation was also studied. Optimum cutting conditions and machine settings for EDM were chosen for machining CFRP composites.

DOI： 10.1080/10910344.2015.1133914

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Precision Engineering  

DOI： 10.2493/jjspe.82.907

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

In this study, the movements of thin tungsten wire electrode during fine wire EDM were investigated by direct observation using a high-speed camera. The results showed that the amplitude in the direction parallel to the machining direction was a little larger than that in the perpendicular one. Also, the backward wire deflection could be confirmed even in fine wire EDM. Furthermore, the wire vibration mode was found out by frequency analysis and the vibration amplitude could be reduced by adjusting the workpiece position to the 3rd order node of the vibration. In addition, the amplitude envelope of wire electrode during the process was clarified. (C) 2016 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.procir.2016.02.266

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

Pure Titanium (Ti) and Ti alloys are the most used biomaterials. However, they have problem for bioactivity because metals have no biofunction. Therefore, adding new function to Ti and Ti alloys are necessary. One method to add new function is the creation of periodic structures on the biomaterial surfaces, which can control cell spreading. Femtosecond laser is one of the useful tools for creating periodic nanostructures, which can be created on metals and semiconductors by self-organizing in the laser focusing spot. In our previous study, the nanostructures could be formed on the Ti plate by using the femtosecond laser with fundamental wavelength of 775 nm. The periodicities of the nanostructures on the Ti plate was approximately 590 nm, which was shorter than the laser wavelength. Cells tests indicated that cell spreading clearly occurs along the grooves of the nanostructures. However, the influence of the periods of the nanostructure on cell spreading has not yet been investigated. It is expected that the periods can be varied by changing laser parameters, such as pulse widths, laser wavelengths, laser fluences, and number of shots. In this study, the periodic nanostructures are created on the Ti plate surface by using the femtosecond laser with fundamental wavelength of 790 nm. Then, influence of the pulse width and number of shots on the periods is investigated. In the experiments, laser beam is focused and scanned on the Ti plate surfaces. The laser irradiated areas are analysed by using a scanning electron microscope (SEM).

DOI： 10.1016/j.procir.2016.02.188

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Surface finishing technology by EDM has recently progressed, and very small surface roughness can be readily obtained by controlling the electrical discharge conditions, or by using metal powder mixed working fluids. In addition, it was reported that EDMed surface using metal powder mixed fluids sometimes has high surface functions, such as high hardness, high corrosion resistance and so on. Therefore, the high functional EDM finished surface is well expected to be applied as a final metal mold surface. In this study, formation of chromium containing layer on the EDMed surface was tried by using chromium powder mixed fluid. Furthermore, the EDMed surface characteristics with chromium powder mixed fluid were experimentally evaluated. (C) 2016 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.procir.2016.02.277

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Processing characteristics of transparent conductive film containing silver nanowires by ns pulsed fiber lasers with various pulse duration were experimentally investigated in the view-points of insulating state and surface quality. The laser fluence achieving the insulation state became smaller with decreasing the pulse duration. Appearance of removed trace area of silver nanowires was varied by the pulse duration, and the removal area ratio of removed trace area to the whole one was evaluated to discuss the surface quality. Small removal area ratio and good insulation state could be performed at a wide processing window at long pulse duration of 200ns. (C) 2016 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.procir.2016.02.189

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Effective shielding method for a wide area is required in the vertical-position remote laser welding of pure titanium. Therefore, shielding effects of ring-type nozzles with two layers for a wide area were numerically and experimentally investigated in the vertical-position setup of workpiece with argon gas. Prevention of incoming air flow outside a ring-type nozzle is effective to increase mass fraction of argon gas. Mass fraction of argon gas could be increased using a ring-type nozzle, in which shielding gas is supplied by open-side injection ports of proper angle at a proper flow ratio of two jetting layers. (C) 2016 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.procir.2016.02.230

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The influence of the surrounding gas conditions on the surface integrity in the micro-drilling of silicon carbide was experimentally investigated using ns pulsed laser of 266 nm wavelength. Moreover, micro-machining characteristics were observed using high-speed shutter and video cameras in the micro-drilling of silicon carbide. The size and intensity of the laser-induced plasma were larger, and the plasma affected area was larger and deeper in argon than that in air. Although the intensity of the plasma was lower in helium than that in other gases, the surface around the drilled hole was roughened by the spread of the plasma in the vicinity of the drilled hole. Debris was removed along the flow field generated by laser shot in the opposite direction to the laser irradiation. The gas flow behavior and the spectrum and intensity of the laser-induced plasma were influenced by the surrounding gas type and pressure. The appearance of plasma generation affected the surface integrity at the circumference of the drilled hole, and the surface integrity was improved by reducing the pressure.

DOI： 10.1007/s00340-015-6060-x

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

EDM finishing techn ology has progressed recently, and very small surface roughness can be obtained by controlling the electrical discharge conditions. Also, EDM using powder mixed fluids can improve the surface characteristics. Therefore, the EDM finished surface is highly expected to be applied as a final metal mold surface. In that case, the characteristics of EDMed surface affects the molding performance and the life of metal molds. As a new surface finishing method by EDM, the characteristics of EDMed surface using a nickel powder mixed fluid was experimentally discussed in this study, since nickel coatings have been widely applied to improve the corrosion resistance and the mold releasability of metal molds. Experimental analysis clarified that the resolidified layer containing nickel content could be formed on the surface by EDM in nickel powder mixed fluid. Also, the water repellency and the releasability of molded resin from the EDM finished surface could be improved.

DOI： 10.4028/www.scientific.net/KEM.656-657.375

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DOI： 10.2493/jjspe.81.1033

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Precision Engineering  

DOI： 10.2493/jjspe.81.1039

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In a large-area electron beam (EB) irradiation method developed recently, high energy EB can be obtained without focusing the beam, and large-area EB with almost uniform energy density distribution of 60mm in diameter can be used for instantly melting and evaporating metal surface. Then, the surface smoothing and surface modification of metal molds made of steel, cemented carbide and ceramics can be performed efficiently. When the large-area EB is irradiated to a sharp edge, the material removal remarkably progresses at the edge due to the heat accumulation and EB concentration there, which leads to the edge rounding. Our previous study clarified that micro-deburring was also possible by using this phenomenon. Moreover, this method would be effective for removal of discontinuous micro burrs generated by thermal machining processes, such as EDM and laser cutting. In this study, the possibility to completely remove micro burrs generated in EDM was experimentally investigated. The difference in micro-deburring characteristics with the type of workpiece material was also investigated. As a result, the EDM micro burrs with a height of about up to 50μm could be completely removed by this method. Furthermore, it was made clear that the magnetic property of workpiece materials greatly influenced the deburring characteristics, and the thermal property such as melting point and thermal conductivity also did.

DOI： 10.4028/www.scientific.net/KEM.656-657.369

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High flow rate in nozzle jet flushing is effective for smooth debris exclusion from the wire EDM gap, but this leads to large wire deflection and vibration, resulting in the wire breakage and low shape accuracy. In this paper, the influence of nozzle jet flushing on wire breakage was experimentally investigated with varying the machined kerf length and machining conditions. Furthermore, the flow fields and debris residence time in the kerf, hydrodynamic stress distributions acting on the wire, and wire deflections were numerically analyzed. Based on the analyzed results, the causes of wire breakage were discussed. (C) 2015 CIRP.

DOI： 10.1016/j.cirp.2015.04.034

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DOI： 10.2493/jjspe.81.435

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DOI： 10.2493/jjspe.81.446

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Trans Tech Publications Ltd  

Glass materials are widely used in products such as optical components and semiconductor devices. In these products, precision welding techniques of glass are required to manufacture small and complicated shape. The laser welding method can perform the joining without an intermediate layer and an adhesive agent. In addition, an ultra-short pulse laser can reduce the heat affected zone with the high space accuracy. However, heating and cooling cycles are repeated even in the case of ultra-short pulsed laser. The temperature distribution and change of molten area are influenced not only by laser energy condition but also focusing condition. Therefore in this study, effects of focusing condition of laser beam on micro-welding characteristics of glass were experimentally investigated by using a picosecond pulsed laser. A usage of object lens with the spherical aberration correction led to a large molten area even at the same pulse energy, which related to the efficient welding of glass materials. An optical system with the spherical aberration correction led to stabilizing the shape of molten area, which resulted in the reliable weld joint.

DOI： 10.4028/www.scientific.net/KEM.656-657.461

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DOI： 10.1299/jsmelem.2015.8._1102-1_

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmelem.2015.8._1104-1_

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DOI： 10.1299/jsmelem.2015.8._1101-1_

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DOI： 10.1299/jsmelem.2015.8._1203-1_

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DOI： 10.1299/jsmelem.2015.8._1204-1_

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

It has been known that wavelength, power density, interaction time and material properties have great influence on processing characteristics in laser material processing, in which materials with higher reflectivity classify into difficult-to-weld materials. In electronic industry, aluminum alloy is widely used as structural components due to its high specific strength, and copper became an important material because of its excellent electrical conductivity. These materials have high reflectivity and high thermal conductivity, which results in instability of energy absorption and processing results. Therefore, welding defects might be noticed in the micro-joining of aluminum alloy and copper. In this paper, the smart laser micro-welding of difficult-to-weld materials such as aluminum alloy and copper were discussed. The combination of a pulsed Nd:YAG laser and a continuous diode laser could perform high-performance micro-welding of aluminum alloy. A pulsed Nd:YAG laser was absorbed effectively from the beginning of laser scanning by pre-heating Nd:YAG laser pulse with the superposition of continuous diode laser, and wide and deep weld bead could be obtained with better surface integrity. As for micro-welding of copper material, stable absorption state could be achieved using a pulsed green Nd:YAG laser, since its absorptivity showed almost constant values with change of power density. A longer pulse duration was effective to achieve not only high absorptivity but also low deviation of absorptivity. The pulse waveform with maximum peak at the early period and a long pulse duration led to stabilizing the penetration depth with less porosity.

DOI： 10.1117/12.2076232

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This paper describes the applicability of large-area EB irradiation method to a new surface modification for metal molds. The previous papers clarified that the surface roughness on wide area uniformly decreased to less than 1 mu m Rz in a few minutes by the large-area EB irradiation. Therefore, the large-area EB irradiation method has high practicability as an efficient surface finishing process for metal molds, and then the EB irradiation equipment has already been introduced into the market for practical use. In this method called EB polishing, the surface material melts and a very thin resolidified layer is formed on the surface. In this paper, the surface structure of EB polished metal mold steel SKD11 was first observed by TEM, and also component analysis was carried out by EDX. Then it was found out that the crystal grain size became small and chromium carbide is uniformly rearranged in the layer. Next, using heat conduction analysis model considering the electron penetration on the surface, the temperature distribution was calculated. The results showed that the surface temperature rapidly raised over its melting point until the end of EB irradiation, and cooled down rapidly. As the important practical surface characteristics for long life of metal mold, resistance to corrosion, water repellency, and the releasability of molded resin from metal mold surface were evaluated. The corrosion resistance and the water repellency could be improved by EB polishing, since the surface structure changes and Cr content distributed uniformly on the surface. Also, the releasability of molded resin from the surface became better. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2014.02.028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN LASER PROCESSING SOC  

The internal modification technique for a sapphire substrate using a sub-nanosecond pulsed fiber laser of 180 ps was experimentally investigated with a normal achromatic focusing lens of 20 mm focal length, and the possibility of a singulation method with this internal modification technique was discussed. The laser beam of 1060 nm was focused in sapphire substrate of 0.4 mm thickness by passing through GaN epitaxial layer grown on the top surface of the sapphire substrate, and the internal modification zone was generated from the stain-finished surface as the bottom surface of sapphire substrate. The laser beam was absorbed from the stain-finished bottom surface, and the absorption point moved in the axis of laser irradiation without moving the focusing optics. The narrow internal modified line less than 5 mu m in width with a high aspect ratio of more than 30 was successfully obtained only by one laser scanning irradiation from the epitaxial layer side. A sapphire wafer could be broken from the internal modified line with less damage of the epitaxial layer by a stress sufficiently smaller than the tensile strength of sapphire. The breaking strength and its dispersion became smaller with increasing number of laser scans.

DOI： 10.2961/jlmn.2014.01.0011

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In compression or injection molding of rubber products, small pieces of residual rubber often remain on the metal mold surface after releasing the product. This is caused by excessive localized adhesion to the mold surface. Therefore, cleaning of metal mold surface must be often performed, which results in longer molding cycle time, and the lifetime of metal mold is often reduced. In this study, the separation forces between molded rubber and metal mold surfaces are measured with a tensile tester to evaluate the releasability of molded rubber from the metal mold surface. Mold surfaces treated by various surface coatings and surface modification methods including EB polishing were tested and compared. Experimental results show that the separation force between molded rubber and metal mold surfaces depends on the true contact area between them and the chemical composition of the metal mold surface. The separation force decreases with a decrease in contact area. The chromium content at the metal mold surface significantly reduces the separation force. EB polishing is one of the most effective surface treatments for metal molds since the real contact area can be decreased while also decreasing the surface roughness of the tool surface in a short time. Electron beam melting is also shown to be an effective method of distributing chromium uniformly on the metal mold surface.

DOI： 10.1007/s00170-013-5415-x

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DOI： 10.2526/ijem.19.22

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DOI： 10.2526/ijem.19.28

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DOI： 10.2493/jjspe.80.419

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DOI： 10.4028/www.scientific.net/MSF.783-786.2792

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN LASER PROCESSING SOC  

The development of advanced materials with superior high thermal properties and high specific strength has led to new metal matrix composites (MMCs) as a great attractive material in electrical and electronic industries. In order to manufacture more practical component from MMCs, a technique for joining MMCs to other similar composites or monolithic materials is strongly required. Therefore, the reliable and economic joining technique is investigated to increase the applications of MMCs. In this study, the overlap welding of pure aluminum and super thermal conductive (STC) aluminum-graphite composite was experimentally and numerically investigated by using a pulsed Nd: YAG laser. In order to discuss the welding of dissimilar materials with different thermophysical properties, the temporal change of heat input was controlled by arranging the laser pulse waveform. The porosities and bumps were observed as the remarkable weld defects in the welding process without a pulse control. On the other hand, the weld bead was largely free of defects, and a size of bump was relatively small with the appropriate controlled pulse waveform. It was clarified that the laser welded joint of an aluminum and a STC aluminum-graphite composite could be successfully achieved with the better weld penetration stability by the appropriate controlled pulse waveform.

DOI： 10.2961/jlmn.2013.01.0018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

In the electrical discharge machining (EDM) process, thin tool-electrodes are constantly gaining much importance due to the growing demand for manufactured parts with more functional characteristics and with small geometrical dimensions for applications in many work fields. This article highlights the utilization of the EDM process using multi-thin tool-electrodes with diameters of 0.3, 0.5 and 1.0 mm and different lateral spaces (3.0 to 0.8 mm). This machining technology requires using more than one tool-electrode in the same time for fabrication of microholes with high process performance and productivity. One of the principal aims of the experimental investigations of this article is to determine the minimum lateral spacing required between tool-electrodes for reducing process costs under acceptable conditions related to the surface of the machined workpiece. Tool-electrode wear and material removal rate are investigated as result of these experiments under adjustment of different process parameters. The beneficial effects of this machining process are also highlighted. The first experimental results of EDM with multi-thin tool-electrodes indicate some technical and economical advantages as a machining process.

DOI： 10.1080/10910344.2012.747916

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Glass materials have been widely used in optics, MEMS, electronics and biomedical applica-tions because of their excellent optical, mechanical and chemical properties. Fusion welding by ul-trashort pulsed laser has been proposed as a promising technique for glass joining, since joining can be accomplished without an intermediate layer and mechanical contact. However, to apply a fusion welding technique by ultrashort pulsed laser as a reliable joining method, it is important to under-stand the mechanical properties of the weld seam since glass materials are very sensitive to tempera-ture gradients. Therefore, a method of evaluating the weld seam in the fusion welding of glass by picosecond pulsed laser was discussed, and its mechanical strength was investigated. A larger opti-cal contact area had a great influence on the shear load of the weld seam, while a smaller optical contact area could reduce the influence of the contact area on the measurement of shear load. There-fore, it was important to reduce the optical contact area to accurately evaluate the shearing strength of weld seam. The mechanical strength of the weld seam reduced at a low pulse repetition rate. High bending strength and shear stress could be obtained at a proper pulse repetition rate.

DOI： 10.2961/jlmn.2013.01.0013

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Laser microwelding has been an essential tool with a reputation of rapidity and precision for joining miniaturized metal parts. In industrial applications, an accurate prediction of weld bead geometry is required in automation systems to enhance productivity of laser microwelding. The present work was conducted to establish an intelligent algorithm to build a simplified relationship between process parameters and weld bead geometry that can be easily used to predict the weld bead geometry with a wide range of process parameters through an artificial neural network (ANN) in laser microwelding of thin steel sheet. The backpropagation with the Levenberg-Marquardt training algorithm was used to train the neural network model. The accuracy of neural network model has been tested by comparing the simulated data with actual data from the laser microwelding experiments. The predictions of the neural network model showed excellent agreement with the experimental results, indicating that the neural network model is a viable means for predicting weld bead geometry. Furthermore, a comparison was made between the neural network and mathematical model. It was found that the developed neural network model has better prediction capability compared to the regression analysis model. © 2013 Mohd Idris Shah Ismail et al.

DOI： 10.1155/2013/415837

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In this study, the electrical discharge machining (EDM) characteristics and its removal mechanism for one and two directional carbon fibre reinforced plastic (CFRP) composite was evaluated. Also, an investigation about the influence of carbon fibre direction to machining direction was discussed to attain high performance of EDM process. Then EDM characteristics with two different combinations of machining direction and carbon fibre direction were compared. EDM machining characteristics such as material removal rate, electrode wear rate, surface roughness and SEM images were determined. Experimental results clarified that the material removal mechanism in the EDM for one directional CFRP when the machining direction is perpendicular to the fibre direction is different from that in parallel machining. Also, the EDM machining for two directional CFRP is different from that for one direction. Therefore, efficient EDM for CFRP is possible by selecting appropriate machining direction to fibre direction and the type of CFRP according to its fibre direction. Copyright © 2013 Inderscience Enterprises Ltd.

DOI： 10.1504/IJMMM.2013.054272

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DOI： 10.2493/jjspe.79.950

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

The sputter deposition of ceramic film on metal mold steel surface by large-area electron beam (EB) irradiation was discussed. The large-area EB has high energy density enough to generate plasma above the workpiece surface during the surface smoothing process, which causes the sputtering of target material set near the workpiece surface. The sputter deposition of target material with simultaneous surface melting and resolidification of workpiece surface by large-area EB would improve the adhesion between the deposited film and the workpiece. Short ceramic tube made of alumina or zirconia as a target was put on the substrate surface of steel, and large-area EB was irradiated to the surface. The workpiece surface component and structure after the irradiation were investigated using EDX and XRD analysis, in order to discuss the possibility of large-area EB irradiation as a new coating method. (C) 2013 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.procir.2013.03.053

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DOI： 10.4028/www.scientific.net/MSF.783-786.2792

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

In a large-area electron beam (EB) irradiation method developed recently, high energy EB can be obtained without focusing the beam. Then the large-area EB of 60mm in diameter with uniform energy distribution can be used for instant melting of metal surface. The previous studies clarified that the surface smoothing of metal mold made of steel, cemented carbide and ceramics can be performed efficiently. Also this method can be applied to the surface finishing of biomaterials, such as stainless steel and titanium alloy. In this method, the sharp edge is rounded to about half hundred microns in radius under relatively high energy density conditions, since the material removal remarkably progresses there due to the electron concentration and heat accumulation at the edge. In this study, the possibility of micro deburring was investigated by using the preferential edge removal effect in the large-area EB irradiation. Experimental results showed that the micro-deburring was possible by large-area EB irradiation, and the burr height decreased with increasing the energy density of EB and the number of irradiation. The burr of about 10 mu m generated in EDM could be removed completely. Furthermore, micro-burrs at the edge of several small holes could be removed at once. (C) 2013 The Authors. Published by Elsevier B. V.

DOI： 10.1016/j.procir.2013.01.004

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

High efficient and precise slicing method is required for the slicing of silicon carbide ingot. The newly developed multi-wire electrical discharge slicing method would decrease the kerf width and the cracks generated on machined surface. However, much higher wire tension is required in order to reduce wire vibration and to perform a smaller kerf width. Thin wire electrode with round section does not have enough cross sectional area under the high wire tension condition. Therefore, a wire electrode with track-shaped section was proposed and applied to the wire EDM slicing of silicon carbide ingot. The running control of wire electrode with track-shaped section was experimentally investigated. The side support method with fixture plates could decrease the kerf width by brass coated steel wire electrode with track-shaped section. The parallel drawing type traverser and the short distance setting points of side support fixture plates could perform the smaller vibration of wire electrode with track-shaped section and the decrease of kerf width. (C) 2013 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.procir.2013.03.052

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In this study, the thermal deformation of thin stainless steel sheet was investigated in the bead-on-plate welding by using a single-mode fiber laser with a Galvano scanning system. The numerical simulation was developed to calculate the temperature and stress fields, and its deformation characteristics were discussed. It was suggested that the specimen firstly deformed downward in the same direction of laser irradiation, and then deformed in the reversed direction after laser scanning. The final deformation angle in the negative direction, which is concave shape from the view direction of laser irradiation, was generated under the welding mode of conduction and quasi-penetration for 50 mu m thickness sheet. On the other hand, the positive angle of final deformation angle was obtained under full-penetration welding mode, and the extreme small distortion could be achieved by the proper weld bead geometry in micro-welding of thin sheet. It was also confirmed that the similar weld bead geometry was resulted in both quasi-penetration and full-penetration welding mode for 20 mu m thickness sheet, but the final deformation angle tendency was different in 50 mu m and 20 mu m specimen thickness. It was clarified that the welding deformation was influenced not only by weld bead geometry but also by specimen thickness. (C) 2013 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.procir.2013.03.054

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Laser micro-welding has proven to be a very successful tool for micro-joining in the electrical and electronic industries, where the miniaturization, the high strength and the high heat resistance are constantly requested. Recently, a flexible printed circuit (FPC) is expected as a new connection technology between electrical conductors according to the improvements of reliability and controllability with the diversification of the design concept. In this technology, it is required to weld a several tens μm thickness of FPC and a several hundreds μm thickness of metal electrode. This material combination accompanies the difficulty to control the welding phenomenon due to the differences of thermal property and heat capacity. As a good alternative, laser micro-welding has advantages of non-contact tool, low heat distortion and consistent weld integrity. In this study, the overlap welding of thin copper circuit on a polyimide film and a thick brass electrode was experimentally and numerically investigated by using a pulsed Nd:YAG laser. In addition, the shearing stress of overlap welding was evaluated with and without the control of pulse waveform, which can provide a well-directed controlling of the heat input with high energy density. The results showed that a porosity was observed as the major weld defect in the welding process without a pulse control. However, the appropriate controlled laser pulse configuration of micro-welding could remove the weld defects in the molten zone, improve the weld penetration stability and increase the weld strength. The potential benefits of controlled pulse waveform were discussed for the direct laser micro-welding process. It is clarified that the direct laser micro-welding of a thin copper circuit on a polyimide film and a thick brass electrode could be successfully achieved by appropriate controlled pulse waveform and heat input. © KSPE and Springer 2012.

DOI： 10.1007/s12541-012-0041-3

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Precision micro-machining without crack and heat affected zones is required in order to use high-performance materials such as silicon and silicon carbide, and it is expected that the higher harmonics of the Nd:YAG laser can perform precision micro-machining due to its high photon energy. However, even by using the harmonics of the Nd:YAG laser, a heat affected zone is inevitable due to the plasma generation. In order to reduce the influence of plasma on the processing results, it is important to understand the generation mechanism of plasma. Therefore, the laser induced plasma in micro-drilling of silicon carbide was observed by a high-speed shutter camera, and the influence of laser wavelength and surrounding conditions on the machining characteristics were experimentally investigated. The removal depth increased with decreasing wavelength and the surrounding gas pressure. The surface integrity was improved by the combination of shorter wavelength and reduced pressure conditions. The behavior of laser induced plasma was different from the wavelength of the laser beam and the surrounding gas pressure. Under atmospheric pressure conditions, the plasma grew greatly and affected the wider surface around the drilled hole with increasing wavelength. Under reduced pressure conditions, there was little difference in plasma size by wavelength, and the affected zone around the drilled hole became relatively smaller. It became clear. that a low surrounding gas pressure and shorter wavelength were important to obtain better surface integrity and highly efficient processing.

DOI： 10.4028/www.scientific.net/KEM.516.36

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

In a wire EDM using a thin wire electrode, better exclusion of debris from the machined kerf is important in order to maintain stable machining performance, since the area of spark generation is along a line and very small. When large amounts of debris stagnate in the gap, secondary discharges possibly occur and these discharges easily concentrate on the same location, which leads to unstable machining performance, wire breakage, low machining rate and a low shape accuracy.
Conventionally, the exclusion of debris is carried out by jet flushing with an upper and lower nozzle. However, the flow field of machining fluid in the kerf due to the jet flushing and the effect of jet flushing conditions from the nozzles on debris exclusion have not yet been sufficiently examined. This study aims to clarify the flow field in the machined kerf by computational fluid dynamics (CM) and to propose new jet flushing methods for smooth debris exclusion in the wire EDM. The effects of workpiece thickness and machined kerf length on the flow field of working fluid in the kerf under conventional jet flushing conditions are discussed. Then, jet flushing with a tilting nozzle is proposed in order to decrease the debris stagnation area near the wire electrode. As a result, by using the tilting nozzle, removal rate can be improved because of the smooth debris exclusion.

DOI： 10.4028/www.scientific.net/KEM.516.73

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANSACTION PUBLISHERS  

A newly developed multi-wire electrical discharge machining (EDM) method would accomplish the high performance slicing of silicon and silicon carbide with a narrow kerf width under a clean process environment. However, the thinner wire is challenging process with a normal round shape wire electrode. Therefore, a new wire electrode with track-shaped section was proposed in order to satisfy both the narrow kerf width and the high wire tension even in the case of thin wire electrode. In this study, the running control of wire electrode with track-shaped section was experimentally investigated, and the possibility of proposed process was discussed. A brass coated steel wire electrode with track-shaped section of aspect ratio 1:2 could perform the smaller vibration and the stable running up to 300 m/min. The side support method with fixture plates could improve the running stability of brass coated steel wire electrode with track-shaped section and reduce the kerf width. The brass coated steel wire electrode with track-shaped section could accomplish the uniform and straight kerf shape by increasing the wire tension.

DOI： 10.4028/www.scientific.net/KEM.523-524.287

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2493/jjspe.78.72

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Scattering velocity and angle of spatter were investigated by recognizing and tracking spatter with the high-speed video observation. The spatter movement was observed by two high-speed video cameras, and analyzed by twodirection tracking method, in which the 3D tracking lines of spatter were constructed in the forward and backward frames and the actual trajectory of individual spatter was obtained by averaging those tracking lines. It made clear that the initial velocity of spatter was less than the speed of sound and mainly ranged from 75m/s to 200m/s. The velocity of spatter showed the slight correlation with the angle. (C) 2012 Published by Elsevier B.V. Selection and/or review under responsibility of Bayerisches Laserzentrum GmbH

DOI： 10.1016/j.phpro.2012.10.102

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A pulsed laser of 532 nm wavelength with ms range pulse duration was newly developed by second harmonic generation of diode pumped pulsed Nd:YAG laser. High electro-optical conversion efficiency more than 13% could welding be achieved, and 1.5 kW peak power green laser pulse was put in optical fiber of 100 mu m in diameter. In micro-welding of 1.0 mm thickness copper plate, a keyhole welding was successfully performed by 1.0 kW peak power at spot diameter less than 200 mu m. The frequency doubled pulsed laser improved the processing efficiency of copper welding, and narrow and deep weld bead was stably obtained. (C) 2012 Published by Elsevier B. V. Selection and/or review under responsibility of Bayerisches Laserzentrum GmbH

DOI： 10.1016/j.phpro.2012.10.076

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：JAPAN SOC PRECISION ENGINEERING-JSPE  

This study aims to develop a new lens system using an integrated arrangement of micro-prism-cell (MPC) and to obtain similar focusing performance as an optical lens. In this lens system, the respective prisms have different apex angle which is fabricated by precision processing. Further development of this system would make it possible to manufacture a multifocal lens in a small area, which leads to wide applications not only in optical devices, such as glasses and intraocular lenses, but also in pickup lenses for optical storage and so on. In this study, a new software was first developed to design a micro-prism-array (MPA), in which the apex angles of respective MPC were precisely computed. Based on the computed design, the photo-resist shape pattern was produced on trial by reactive ion etching (RIE). Then, the formation of a smooth prism slope was tried by using the resist mask whose shape was whittled away with an O-2 (oxygen) RIE. Then, as a preliminary experiment, the apex angle was experimentally optimized with varying the etching conditions. In the experiment, the size of each MPC was set to 10 mu m, and the formation of the MPC, which had different apex angles ranging from zero to about 15 degrees was achieved by four process stages of the RIE. A good focusing performance of the manufactured MPA could be obtained despite a diffusion of light. Nevertheless, the performance is not yet up to the specified design, and there remain some problems to be solved in order to achieve precise focusing performance with the MPA.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：JAPAN SOC PRECISION ENGINEERING-JSPE  

In the wire EDM using a thin wire electrode, the reduction of wire vibration is important to achieve a high-precision machining, since large amplitude of wire vibration leads to large kerf width, low shape accuracy, rough machined surface and high risk of wire breakage. In this study, the movements of wire electrode are directly observed by using a high-speed video camera in order to clarify the wire vibration in fine wire EDM for thin workpiece. The results shows that the wire vibration amplitude during the process increases with wire running speed and flow rate of jet flushing but decreases with wire tension. Also, the wire behavior during process is almost 1st order string vibration. Furthermore, the wire vibration frequency increases with not only the wire tension but also the discharge pulse frequency.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：JAPAN SOC PRECISION ENGINEERING-JSPE  

Cemented tungsten carbide with nickel binder is often applied to the metal mold for electronic parts due to its non-magnetic feature. However, it is difficult to use conventional methods applied to metal molds made of steel for the surface finishing or modification of cemented tungsten carbides in some cases. The large-area EB irradiation for conventional cemented tungsten carbide with cobalt binder was studied in our previous papers. In this paper, surface finishing and modification of cemented tungsten carbide with nickel binder were investigated, and the effects of EB conditions on the surface characteristics were discussed. The experimental results indicated that the surface roughness decreased and the surface glossiness increased by the large-area EB irradiation. Also, the water repellency and the releasability of molded resin from the surface could be improved under proper EB conditions.

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In this study, the thermal deformation of thin stainless steel sheet in laser micro-welding were experimentally and numerically investigated. The welding deformation was experimentally evaluated using a single-mode CW fiber laser with a high-speed scanning system. The numerical simulation was developed to calculate the temperature, stress and deformation fields. It was clarified that the laser irradiation condition has a significant effect on the welding mode and stress field. In addition, the thermal deformation was influenced by the weld bead geometry and residual stress distributions, and the final deformation was formed by residual stress and plastic deformation. It was found that the tensile stress was generated around the molten zone and balanced by the compressive stress in the base material.

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Cemented carbide has many excellent properties. However, it is sometimes difficult to apply conventional surface finishing or surface modification methods for the cemented carbide. The possibility of surface modification by large-area electron beam irradiation, namely EB polishing was discussed. The surface structure of the EB polished cemented carbide was observed by TEM. The hardness and the water repellency were tested. Also, the separation force of molded resin from the surface was measured for evaluating the releasability of the resin. The water repellency and the releasability of the molded resin could be improved by EB polishing, because the surface structure changed. (C) 2011 CIRP.

DOI： 10.1016/j.cirp.2011.03.107

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DOI： 10.2526/jseme.45.64

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DOI： 10.2526/jseme.44.52

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TECHNISCHE RUNDSCHAU EDITION COLIBRI LTD  

In fine wire EDM using thin wire electrode, uniform distribution of spark location is necessary to achieve stable machining performance. However, it is difficult to precisely evaluate the distribution of spark location by the conventional branched electric current method when the workpiece is thin. A new evaluation method by using a high-speed video camera is proposed. The locations of spark are measured by analyzing the recorded images. Then the effects of machining parameters, such as servo voltage, pulse interval time, wire running speed and others on the distribution of spark location are investigated. The possibility of evaluating the wire vibration is also discussed. (C) 2010 CIRP.

DOI： 10.1016/j.cirp.2010.03.073

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DOI： 10.2493/jjspe.76.1393

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SHANGHAI JIAO TONG UNIV PRESS  

Unconventional methods of cutting based on ultrasonics, laser, and water jet mechanisms that might be used in orthopaedic surgery are discussed. Their advantages include no or little contact with bone or tissue that is to be cut, the application of less mechanical force compared to traditional techniques, and reduction in localised heat effect in the region undergoing surgical cutting. Their limitations and merits are identified.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SHANGHAI JIAO TONG UNIV PRESS  

Cemented carbide has many excellent properties, such as high strength, high hardness and so on. However, it is difficult to apply conventional surface finishing or surface modification methods for the cemented carbide. In this paper, a new surface finishing by large-area electron beam (EB) irradiation is proposed, and the possibility of surface smoothing and surface modification was discussed. The experimental results clarified that high-efficient surface smoothing was possible under the proper EB conditions. The repellency and the releasability of molded resin could be improved by large-area EB irradiation.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SHANGHAI JIAO TONG UNIV PRESS  

Carbon fiber reinforced plastic (CFRP) is a very strong and light composite material, and it has many applications in aerospace and automotive fields. However conventional mechanical machining methods, such as cutting and grinding have some problems; delaminating, splintering, burrs of machined surface and short tool life. Electrical discharge machining (EDM) is an effective alternative for machining difficult-to-cut materials. In this paper, the EDM characteristics, such as material removal rate, electrode wear rate and surface roughness for CFRP were experimentally investigated with varying discharge peak current and pulse duration.

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DOI： 10.2526/jseme.43.179

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This paper deals with EDM characteristics of newly develops electrically conductive ceramics. Titanium boride (TiB2) is widely used as die and mold materials because of its high hardness, high-temperature resistance and so on. The EDM characteristics of the titanium boride, such as electrode wear rate, removal rate and surface roughness were investigated. Experimental results show that EDM with low electrode wear rate is possible when copper electrode is used with positive polarity. The removal rate becomes much higher when graphite electrode is used with negative polarity.

DOI： 10.4028/www.scientific.net/KEM.407-408.636

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TECHNISCHE RUNDSCHAU EDITION COLIBRI LTD  

In wire EDM, better exclusion of debris from the machined kerf is very important to obtain a stable machining performance. The purpose of this study is to investigate the fluid flow in the kerf and better jet flushing conditions of working fluid from the nozzles. The flow field and the debris motion in the kerf were analyzed by computational fluid dynamics (CFD) simulation, comparing with the observation by high-speed video camera. The influence of flow rate of working fluid from nozzles and the nozzle standoff distance on flow field in the kerf and debris particle motion were discussed. (C) 2009 CIRP.

DOI： 10.1016/j.cirp.2009.03.003

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A new surface finishing method by large-area electron beam irradiation (EB-polishing) for stainless steels for orthopedic surgical tool was proposed in our previous paper, and it was shown that high-efficient surface finishing was possible by the EB-polishing. In this report, the surface structure of EB-polished stainless steel is analyzed by TEM and EDX. Also, surface modification effects such as resistance to corrosion and blood repellency are evaluated. Then, the applicability of the EB-polishing as a new surface modification method of stainless steel for orthopedic surgical tool is discussed.

DOI： 10.4028/www.scientific.net/KEM.407-408.339

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

The purpose of this study is to develop a new type of wire electrode, in which piano wire with very high tensile strength is coated with electrically conductive layer, such as brass or zinc, in order to attain high speed and high precision wire EDM. In this report, using a trial-made thin wire of 50 mu m in diameter, the optimum thickness and quality of brass layer were experimentally investigated for higher performance fine wire EDM. Furthermore, the influence of the tensile strength of piano wire used as a core wire was discussed. As a result, the coated brass with copper content of 60-70% is effective and the thickness of coated brass is needed to be more than 1.45 mu m for high removal rate.

DOI： 10.1299/jamdsm.2.735

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DOI： 10.2526/jseme.42.122

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DOI： 10.2493/jjspe.74.385

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TECHNISCHE RUNDSCHAU EDITION COLIBRI LTD  

Surgical tools and jigs are initially machined by multi-axis milling. Then surface finishing is carried out mainly by hand lapping. As these tools undergo repeated use, the removal of burrs, scratches and rust from the surfaces is also performed manually after each operation. These finishing processes are time-consuming and costly. In this study, a new finishing method by large-area electron beam irradiation is proposed. Electron beam (EB) with high energy density can be obtained without focusing the beam, and large-area EB can be used for instantly melting or evaporating the metal surface. Stainless steel for surgical tools and jigs was treated by the large-area EB irradiation method. The experimental results show that highly efficient surface smoothing of stainless steels by large-area EB irradiation may be achieved. In addition, the resistance to corrosion and blood repellency can be improved simultaneously with surface smoothing. (c) 2008 CIRP.

DOI： 10.1016/j.cirp.2008.03.062

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

A new surface modification for bio-titanium alloy products by electron beam (EB) polishing is proposed. In this EB polishing method, high energy density EB can be irradiated without concentrating the beam. Therefore, large-area EB with a maximum diameter of 60mm can be used for instantaneously melting or evaporating metal surface. Experimental results made it clear that surface characteristics, such as repellency, corrosion resistance and coefficient of friction could be improved simultaneously with the surface smoothing in a few minutes under a proper condition. Therefore, EB polishing method has a possibility of high efficient surface smoothing and surface modification process for bio-titanium alloy.

DOI： 10.1299/jamdsm.2.694

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

A new polishing method by large-area electron beam (EB) irradiation is proposed in this study. In the large-area EB irradiation equipment used here, an EB with high energy density is irradiated without focusing the beam. An EB irradiation in a few microseconds with a maximum diameter of 60 mm can be used for melting metal surface instantly. The experimental results made it clear that the surface roughness decreases from 6 mu mRz to less than 1 mu mRz in a just few minutes under a proper machining condition. The corrosion resistance of metal mold surface also could be greatly improved by large-area EB irradiation. Furthermore it is clarified that even the surface roughness of tilting surface close to 90 degrees could be well improved. Therefore, large-area EB irradiation method has a high possibility to become a high-efficiency polishing method of metal mold. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2006.11.080

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DOI： 10.2526/jseme.41.69

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Language：English   Publishing type：Research paper (international conference proceedings)  

Wide-area electron beam (WAEB) irradiation was proposed as a new surface-finishing process for orthopaedic titanium alloy products. The surface roughness could be reduced from Rz = 10 μm to Rz = 0.7 μm all over the wide circular surface within a diameter of 60 mm in just a few minutes under optimum electron beam conditions. In this paper, the surface structure and the surface characteristics of WAEB-irradiated surface are discussed. The crystal grain size becomes small and the microstructure in the surface vicinity changes under WAEB irradiation. The corrosion resistance and the repellency can be improved simultaneously with the surface smoothing. Therefore, the WAEB irradiation method enables highly efficient surface smoothing and surface modification of orthopaedic titanium alloy. © IMechE 2007.

DOI： 10.1243/09544054JEM574

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：UNIV NEBRASKA-LINCOLN  

A new polishing method by large-area electron beam (EB polishing) is proposed. In the EB polishing, an EB with high energy density is irradiated without focusing the beam. An EB with a maximum diameter of 60 mm can be used for melting metal surface instantly. The experimental results made it clear that the surface roughness decreased from 6 mu m Rz to less than 1 mu m in just a few minutes under a proper condition. In addition, even the tilting surface could be polished very well. Furthermore, the corrosion resistance of metal surface also could be greatly improved.

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DOI： 10.2526/jseme.40.66

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

An extension to the electrical discharge machining method by introduction of radio-frequency plasma is proposed. Sparking with the radio-frequency plasma can be generated in paraffin oil by simple electrical circuitry. In this paper, experimental investigations are described on the fundamental effects of the resonant frequency, type of electrode and workpiece materials on machining characteristics for high performance radio-frequency machining in paraffin oil. The results show that the removal rate and the electrode wear vary with the resonant frequency and type of electrode materials. The surface roughness can be reduced to less than 1 mu m Rz under suitable experimental conditions.

DOI： 10.1016/S0007-8506(07)60390-4

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Language：Japanese  

DOI： 10.2526/jseme.40.169

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：JAPAN SOC PRECISION ENGINEERING-JSPE  

This paper introduces a newly developed CuW electrode for high performance electrical discharge machining (EDM). Conventional CuW electrode used widely for high precision EDM is generally made by melting method, and the mixture ratio of Cu and W is restricted within narrow limits. On the other hand, it can be changed extensively in the case of a new CuW electrode made by powder sintering method. In order to obtain the higher metal removal rate with smaller electrode wear rate, the optimum mixture ratio of Cu and W was investigated. Experimental results show that the EDM characteristics such as, metal removal rate, electrode wear rate and the surface finish for metal mold steel greatly depend on the mixture ratio of CuW electrode. The electrode wear rate could be reduced by using the new CuW electrode with proper mixture ratios, compared with the conventional one, since workpiece material adhered to the electrode end surface during machining and prevented the electrode from wearing with high temperature. Also, better machining stability and better surface finish could be attained under proper mixture ratios of Cu and W Therefore, the new CuW electrode made by powder sintering method has high possibility for higher performance EDM.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

A new finishing process for metal molds by large-area electron beam (EB) irradiation is proposed in this study. In the large-area EB irradiation equipment used here, an EB with high-energy density is irradiated without focusing the beam, and so the EB with a maximum diameter of 60mm can be used for melting or evaporating metal surface instantly. Experimental results show that the surface roughness decreases from 6 mu mRz to less than 1 mu mRz in just a few minutes under proper machining conditions. The corrosion resistance of metal mold surface also could be greatly improved by large-area EB irradiation. Furthermore, the surface roughness of tilting surface close to 90 degrees could be well improved. Therefore, large-area EB irradiation method has a possibility to become a high-efficiency finishing process for metal molds. (c) 2005 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.precisioneng.2004.12.005

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DOI： 10.2526/jseme.39.92_28

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DOI： 10.2493/jspe.71.1399

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER-VERLAG WIEN  

In this paper, unconventional methods of cutting based on ultrasonics, laser, and water jet mechanisms that might be used in orthopaedic surgery are discussed. Their advantages include no or little contact with bone,or tissue that is to be cut, the application of much less mechanical force compared to traditional techniques, and reduction in localised heat effect in the region undergoing surgical cutting. A critical analysis is performed to identify their limitations and merits.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

In deep-hole electrical discharge machining, the electrode jump height and hence the movement of the machining debris inside the side gap affect the wall concavity of the machined holes. In this study, the dielectric fluid flow and the debris distribution in the machining gap caused by electrode jump is analyzed to understand the wall concavity phenomenon of the holes using a computational fluid dynamics (CFD) simulation program. Fluid flow and debris-fluid interaction under low and high electrode jumps are examined and compared. The accuracy of the predictions obtained by the numerical calculation is assessed through comparisons with experimental data.

DOI： 10.1299/jsmec.47.553

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

A new surface finishing process for bio-titanium alloy products by large-area electron beam (LAEB) irradiation is proposed. In the LAEB irradiation equipment, high energy density EB can be irradiated without concentrating the beam. Therefore, LAEB with a maximum diameter of 60 mm can be used for instantaneous melting or evaporating metal surface. Experimental results made it clear that the surface roughness becomes smaller with increasing energy density of beam. Under a proper irradiating condition, the surface roughness of titanium alloy machined with end mill decreases from 10 to 0.8 mum R-z in a few minutes. Moreover, the corrosion resistance can be greatly improved. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2004.02.017

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