森田 昇

In laser cleaving, the thermal stress caused by laser heating and water-jet cooling propagates previously induced cracks in the workpiece material. The laser-cleaving conditions affect the quality of the fracture surface, and therefore, elucidating the relationship between the cleaved surface, cleaving conditions, and crack propagation is essential. Against this backdrop, in this study, we investigated the morphology of the cleaved surface and visualized the crack propagation and stress <italic>in situ</italic> using a high-speed polarization camera. The distance between the glass edge and cleaved surface was varied. When the laser-cleavage line was close to the glass edge, twist hackles were formed on the cleaved surface. The area in which the twist hackles formed on the cleaved surface coincided with the lagging section of the crack front. Furthermore, the twist hackle reached the specimen surface, and the edge of the surface exhibited a sawtooth shape. Observations with the high-speed polarization camera revealed that the internal stress was asymmetric with respect to the crack when the twist hackles were formed.

<p>The authors have reported the laser-induced metal sphere migration in the glass. The metal sphere migrated toward the light source along the optical axis. In this paper, we describe the metal sphere separation by two laser beam illumination from the opposite direction. A stainless-steel sphere in borosilicate glass was heated by two continuous-wave green laser illumination. The laser beam diameter influenced the separation result. One metal sphere was separated to two spheres, when the beam diameter was 60 and 80 µm. When the beam diameter was 100 µm, the one metal sphere was not separated and maintained the shape and migrated toward one direction. When the beam diameter was 20 and 40 µm, laser illumination separate two small sphere from the metal sphere and one metal sphere was left. Hence the one metal sphere separated to three metal spheres. In-situ observation with a high-speed camera and numeral temperature calculation clarified the separation process. Finally, the size control of the metal sphere was demonstrated by changing the beam diameter.</p>

At the joints of the mechanical systems, it is well known that the parameters such as contact stiffness, static friction coefficient, kinetic friction coefficient and attenuation coefficient affect static, kinetic, thermal and motion characteristic of them strongly. In these parameters, the static friction coefficient reigns the character of maximum fixing resistance. However, there’s difficulties for measure the precise static friction coefficient on the coupling surfaces due to tiny contact surface, unstable loading method and moment force acts on the contact surface of the former device. Therefore, we developed novel measurement device and evaluated influence of the surface parameters given to static friction coefficient. Through the validity evaluation, it was confirmed that the new measurement device enables face contact and uniform surface pressure. In addition, there's no moment force by optimizing the loading position of the tangential force. Furthermore, validity of the static friction coefficient was checked and verified that frequency of the sampling rate is fine enough. Finally, we proceeded to applied test with this new measurement device for evaluate the influence of the surface roughness and grinding direction given to static friction coefficient. A pair of die steels and cemented carbides was selected for specimen and static friction coefficient was measured under 60 MPa of contact pressure. Regarding influence of surface roughness, the result showed tendency that rougher surface generates lower value of the static friction coefficient. Now for grinding direction, combination of the specimen ground in orthogonal direction against tangential force showed maximum value and the specimen ground in parallel direction against tangential force showed minimum.

The authors reported that laser illumination to a metal sphere in glass migrated the metal sphere toward the light source. The migration was caused by interfacial tension gradient. In this presentation, we demonstrate the metal sphere separation by the two laser beam illumination from opposite direction. The metal sphere separation was not explained by the interfacial gradient and suggested the existence of pulling force to the light source side.

© Optics & Photonics International Congress 2019. The authors have been proposed metal sphere manipulation in glass. Laser illumination to a metal sphere in glass heated the sphere, and surrounding glass was also heated by the thermal conduction and softened. In this paper, we report a nickel sphere migrated in a crystallized glass. After the migration, the composition of the migration trajectory and nickel sphere was measured with electron probe microanalyzer. As a result, the amount of phosphorous in the trajectory of glass decreased, and the nickel sphere contained phosphorous.

© Optics & Photonics International Congress 2019. We proposed a novel metal sphere manipulation method optically. Continuous-Wave (CW) laser illumination to a sample implanted a metal sphere into a glass. The sample was consisted with a glass, a metal foil, and a heat insulator stacked from the laser source direction. Low-power laser illumination to the metal sphere causes slow migration with transparent trajectory. In this presentation, we discovered that high-power laser illumination caused fast metal sphere migration with black trajectory and strong emission. The emission was analyzed with a spectrometer, and the temperature was estimated to illustrate the difference. The temperature of fast migration was 2900 K and the estimated viscosity of glass was lower than one tenth of slow migration.

© 2018 Japan Society for Precision Engineering. All rights reserved. Using electric field-assisted solid-state ion-exchange technique, metal ions were doped into a borosilicate glass and a buried metal precipitation thin layer was formed in the glass substrate. In this study, silver ions were doped into glass surface by voltage application using the silver foil as an anode (referred to as forward voltage). After ions doping by forward voltage application, a buried silver layer was formed in a glass substrate by additional voltage application with opposite direction to the case of doping (referred to as reverse voltage). Because the silver layer is electrically conductive and surrounded by glass matrix with high electric resistivity, the formed layer can be used as a buried electrical circuit in glass substrate. In order to form multi silver layers in glass, we alternatively doped silver and sodium ions into glass surface. In the case of sodium doping, a soda-lime glass sheet was used as a sodium ion source. Doped sodium ions exchanged the sites occupied by silver ions which doped in advance. As a result, we successfully formed the multi layered structure consisted of silver-rich and sodium-rich layers. In addition, two silver layers separated by sodium-lich layer were formed by reverse voltage application.

<p>Turning with suppressing thrust force has been proposed as a method of processing a micro-shaft. Advantages of thrust force free cutting have been demonstrated by turning micro-shaft (diameter: ~0.05 mm). Although the feed rate is a small value in the previous research, the processing efficiency has not been discussed because the processed shaft is small. If the long shaft is machined, it is indispensable to increase the feed rate to improve the machining efficiency. Therefore, in this research, we confirmed whether the suppression of thrust force was possible with high feed rate to expand the application range of thrust force suppression turning. The condition of suppressing thrust force by turning the long shaft of the medium diameter (~1 mm) was chosen, and the range of the small deformation by suppressing thrust force was clarified. It was also found that deflection due to principal cutting force also caused dimensional error even when thrust force was suppressed.</p>

In this study, a novel method is proposed for patterning the surface of a single-crystal diamond in the sub-micrometer scale using a combination of focused ion beam (FIB) and deep ultraviolet (DUV) laser irradiations. The surface area of the diamond irradiated by the FIB was selectively machined using a low power DUV laser, whereas the non-FIB-irradiated area was hardly machined. Hence, diamonds can be patterned at the sub-micrometer scale by selectively machining the FIB-irradiated area using lasers. To investigate the machining characteristics in this process, the effects of the FIB and DUV laser-irradiation parameters were investigated. Consequently, the shape of the DUV-irradiated area was improved by applying the gallium removal step; debris was not formed. In addition, a structure with a maximum depth of approximately 80 nm was fabricated. The damage density induced by the FIB irradiation was employed to determine the depth induced by the FIB; the depth obtained using this method is more than twice that of the heating technique in air. A concave structure was fabricated based on these results. The results indicate that the proposed method is effective for fabricating sub-micrometer-scale structures on diamond surfaces. (C) 2017 Elsevier Inc. All rights reserved.

We have developed a novel method to synthesize fibers and nanoparticles of silica glass using a continuous-wave laser. The synthesis process operates through continuous-wave laser backside irradiation (CW-LBI) of a glass substrate. In CW-LBI, a spindle-shaped emission is generated in the glass bulk along the optical axis; the emission propagates toward the light source as a confined plasma. The emission and its surroundings contain vaporized and molten glass. When the laser irradiation continues for a sufficient duration, the emission forefront reaches the glass surface, at which point vaporized and molten glass are ejected explosively. The ejected glass forms fibers and nanoparticles. Some of the nanoparticles become attached to the fiber surfaces during the explosion. The fiber diameters range from hundreds of nanometers to more than 10 mu m. The particles on the fiber surfaces have diameters of tens of nanometers. A spindle-shaped hole remained in the glass substrate after the ejection, which had a depth of similar to 3.8 mm. This result indicated that the ejected materials originated from deep inside the glass bulk. High-speed camera observations of the ejection process and scanning electron microscopy of the ejected materials indicated that the fibers formed from the extraction from molten silica glass and particles formed by aggregation of vaporized silica glass.

Pulsed-laser-induced glass fiber generation has been reported. We demonstrate a novel glass fiber generation technique by continuous-wave laser illumination and reveal the generation mechanism. In this technique, borosilicate glass, metal foil, and a heat insulator are stacked and clamped by a jig as the sample. Glass fibers are ejected from the side surface of the borosilicate glass by laser illumination of the sample from the borosilicate glass side. SEM observation shows that nanoparticles are attached on the glass fibers. High-speed imaging reveals that small bubbles are formed at the side surface of the borosilicate glass and the bursting of the bubble ejects the fibers. The temperature at the fiber ejection point is estimated to be similar to 1220 K. The mechanism of the fiber ejection includes the following steps: the metal thin foil heated by the laser increases the temperature of the surrounding glass by heat conduction. Since the absorption coefficient of the glass is increased by increasing the temperature, the glass starts to absorb the laser irradiation. The heated glass softens and bubbles form. When the bubble bursts, molten glass and gas inside the bubble scatter into the air to generate the glass fibers.

Pulse electrochemical nanopatterning, a non-contact scanning probe lithography process using ultrashort voltage pulses, is based primarily on an electrochemical machining process using localized electrochemical oxidation between a sharp tool tip and the sample surface. In this study, nanoscale oxide patterns were formed on silicon Si (100) wafer surfaces via electrochemical surface nanopatterning, by supplying external pulsed currents through noncontact atomic force microscopy. Nanoscale oxide width and height were controlled by modulating the applied pulse duration. Additionally, protruding nanoscale oxides were removed completely by simple chemical etching, showing a depressed pattern on the sample substrate surface. Nanoscale two-dimensional oxides, prepared by a localized electrochemical reaction, can be defined easily by controlling physical and electrical variables, before proceeding further to a layer-by-layer nanofabrication process.

Defect-free glass separation techniques are in strong demand in glass processing industries. In this study, we intended to observe the internal stress field during/after wheel scribing of a glass sheet using the photoelastic method. First, we visualized the crack propagation behavior in a 0.7-mm-thick non-alkali glass sheet during mechanical scribing with a 2.0-mm-diameter serrated diamond wheel using highspeed imaging techniques. The observation results under various applied load conditions showed that the crack propagation behavior changed dramatically at a load of approximately 9-10 N; the generated crack hardly propagated in the thickness direction under lower load conditions, in contrast to the rapid propagation under higher load conditions. The fracture surface morphology that was observed after cleavage also changed, from damaged to defect-free surfaces with increments in the applied load around the transition point (9-10 N). This result indicated that the fracture surface morphology was determined by the crack propagation behavior. Second, the birefringence phase difference was measured from the upper side of the glass sheet to enable understanding of the stress fields induced by scribing wheel indentations. As a result, the phase differences that were distributed along the scribe line were shown to differ depending on the applied loads; the phase difference changed little under lower load conditions, but vanished immediately under higher load conditions. Therefore, these differences were dependent on whether or not rapid crack propagation occurred. The measured phase difference distribution thus included information about the crack propagation behavior, and this information could be used as a criterion for estimation of the fracture surface morphology. An in-process estimation method for the fracture surface morphology during mechanical wheel scribing was therefore developed based on highspeed polarization imaging techniques. (C) 2016 Elsevier Inc. All rights reserved.

Wheel scribing techniques were commonly used for glass separation. We have studied on the internal stress field during/after wheel scribing using the photoelastic method. Internal stress data obtained by photoelastic method was integrated data of the light progression, and internal stress induced by a scribing wheel distributed three-dimensionally. This characteristic complicates the explanation of the photoelastic data. In this paper, we investigate two dimensional internal stress fields by the indentation of a wedge on a thin glass sheet. As a result, birefringence and azimuthal angle was obtained during/after the indentation. Internal stress by the plastic deformation was observed. First, median cracks were propagated after the indentation, then lateral cracks were propagated. The internal stress was released along with the crack propagation.

Numerical analysis revealed the thermal behavior during the laser joining of two glass plates using a low melting point glass frit as an adhesive. The proposed model is a structure consisting of a straight line glass frit sandwiched between glass plates. The numerical solutions of three associated heat equations were provided by the finite difference method. The constant heat flux model predicted the temperature at the contact interface between the glass frit pattern and the glass plate. The influence of heat source shape on temperature distribution was compared using circular and elliptical beams. Irradiation with the elliptical beam extended the softening domain of the glass frit pattern further than the circular beam. The increase in softening domain depended on the major diameter of the elliptical beam. Thermal diffusion had no influence on the glass plate domains at distances greater than 1 mm from the edge of the glass frit pattern. Laser frit sealing is an effective means of resolving the issue of heat influence on electronic devices.

Texturing on a surface of cutting tools is an effective way to improve friction and resultant machining performances of the tool. This paper presents the machining performance of a textured diamond cutting tool at various machining parameters. The textures, which had width of 1.8 µm and 32 nm, were fabricated on the diamond tool surface utilizing the focused ion beam irradiation and subsequent heat treatment. Machining experiments of nickel phosphorus was conducted to evaluate the effect of the machining condition on the texture effect. The cutting force can be reduced by the texture. This effect was different due to the cutting speed, and significant effect was observed at low cutting speed. In addition, unevenness on the machined surface was improved by texturing, due to the reduced shear deformation at low cutting speed. These results indicate the effectiveness of the developed textured diamond tool, and the significant effect was obtained at low cutting speed.

This paper presents the fabrication method and machining performance of a textured diamond cutting tool. To improve the machining performance, a texture was fabricated on the rake face of the diamond tool with a depth of 43 nm and width of 1.8 mu m by utilizing a focused ion beam (FIB) followed by heat treatment. In addition, a FIB-induced non-diamond phase that adversely affects the machining performance was removed. A machining experiment using aluminum alloy and nickel phosphorus was conducted to evaluate the proposed method. A significant decrease in friction was observed at the tool-chip interface after texturing. This corresponds to a reduced cutting force, which indicates that the machining performance of the tool was improved by texturing. The magnitude of the effect depends on the shape and direction of the texture. The textured tool was able to machine a surface topography similar to that with a non-textured tool, which indicates that the texture effect can be obtained while maintaining the quality of the machined surface by fabricating the texture far from the cutting edge. (C) 2016 Elsevier Inc. All rights reserved.

We proposed a technique to manipulate a metal particle in glass optically. The glass in the neighborhood of the laser-heated metal particle softened; hence, the metal particle migrated in the glass. In our numerical calculation, the temperature difference in the metal particle generated the inhomogeneous distribution of the interfacial tension between melted metal particle and softened glass. The inhomogeneous distribution generated driving force. In this presentation, the experimental temperature measurement by using emitted light of the migrating metal particle in glass was discussed. The temperature was approximately 2400 K and corresponded with the numerical calculated temperature reported before.