Key Engineering Materials Vols. 523-524

Abstract: High-speed orthogonal cutting experiments with cutting speeds of up to 200 m/s with a high-speed impact cutting tester of air-gun type are attempted. In this tester, a light projectile with a small built-in cutting tool is loaded into a tube, being accelerated by a compressed gas. The projectile captures the chip that is indispensable to analyze the cutting mechanism. The projectile holding the chip is decelerated by another compressed gas just after finishing the cutting, being stopped without damage in the tube. Successful experiment can be accomplished by setting adequate values of the operation parameters for the experiment, which are the pressure of each gas and the opening and shutting time of the solenoid-controlled valve for each compressed gas. In order to determine the adequate values of these parameters, a ballistic simulator that simulates the velocity and position of the projectile traveling in the tube is developed. By setting the values of these parameters obtained by the simulator, the cutting speed of 200 m/s is achieved when the ambient pressure is set to be a vacuum and helium is used for each compressed gas. This paper describes the ballistic simulator developed and shows the experimental results of the high-speed cutting of aluminum alloy A2017.

Abstract: A diode-pumped solid-state (DPSS) laser, such as a Nd:YAG green laser, has become smaller in size , lower in cost and higher in performance. Therefore, the DPSS lasers are widely used in many industries. For a laser interferometers and secondly length standards, stable light sources are in demand. We have developed 532 nm iodine-stabilized DPSS lasers used for the applications. The lasers have following features ; compact design (D 280×W 170×H 120 mm), high power (3 mW) , high stability ( < 1×10^-10 : allann deviation k=1 at τ=1 sec), and easy operation.

Abstract: Biological cell could be trapped by a single laser beam from an optical fiber end inserted at an angle to a sample chamber. We have already developed an optical trapping system. A temperature stabilized 1480nm cw diode laser was used as the light source. The fiber end had a hemispherical micro-lens with 5μm radius of curvature for focusing the laser beam. These trapping fibers were inserted into a sample cell at an angle. The microsphere, 10μm diameter particle (refractive index 1.4), could be trapped. We theoretically analyzed the optical forces exerted on a microsphere by laser beams. The optical force on a microsphere divides itself into two components, the force in the beam axial direction of the light and a transverse force. The transverse optical force acted to pull the sphere back. We investigated the relation between the pulling force and the inserted angle of an optical fiber into a sample chamber. The microsphere is trapped at the point where the horizontal directed optical forces are balanced. We theoretically verified that the inserted angle of an optical fiber into a sample chamber was important parameter. It was found that a small inserted angle produced a weak pulling force.

Abstract: Optical trapping is a technique that is used to capture, translate, and manipulate microscopic particles, such as dielectric microspheres and cells. This cell manipulation and examination technology can be integrated on a Lab-on-a-Chip device. We have already developed an optically vibration system. The optical vibration system was formed using a temperature stabilized 1480nm cw diode laser. The output of laser light was coupled into optical fibers, which had optical connectors at these fiber ends. The fiber end had a hemispherical micro-lens with 5μm radius of curvature for focusing the laser beam emerging from the optical fiber end. These trapping fibers were attached to xyz manipulators and were inserted into a sample cell at an angle of 35 degrees. The trapped microsphere, 10μm diameter polystyrene particle (refractive index 1.59), could be optically vibrated by controlling laser power emerging from optical fibers. We theoretically analyzed the optical forces exerted on a microsphere by laser beams. Its operating principle is based upon the conservation of photon momentum carried by the incident laser light on a trapped microsphere. From these theoretical results, we verified that our proposed optical manipulation technique was useful for the manipulation of biological cells.

Abstract: A novel single fiber optic tweezers was proposed for cell isolation. Fiber tips were fabricated by dynamic chemical etching. The mechanically cleaved bare single mode fiber was dipped into Hydrofluoric acid containing a protective layer of Toluene at the top. By moving the fiber at variable speeds, a variety of tip shapes could be created. In our experiments, tip angle could be adjusted from 7deg to 55deg. Three-dimensional optical trap of a yeast cell could be formed by the fiber tip with less than 23deg tip.

Abstract: Chemically etched axicon fiber was proposed for two-dimensional cell trapping. We fabricated axicon micro lenses on a single-mode bare optical fiber by selective chemical etching technique. The laser beam from fiber axicon microlens was strongly focused and optical forces were sufficient to move a microorganisms and biological cells without physical contact. The apex angle of the chemically etched fiber axicon microlens was very important parameter for laser trapping. From these experimental results, it was found that our proposed method was a promising tool for the isolation of microorganisms.

Abstract: We present a study of the improvement in interface roughness of platinum/carbon multilayers for X-ray mirrors. The X-ray reflectivity of multilayers strongly depends on interface quality. In an effort to reduce the interface roughness caused by crystallization during deposition, carbon doping of platinum was proposed, and its effectiveness was evaluated. We compared 45-nm-thick single-layer platinum to carbon-doped platinum films. The films were deposited on a silicon (100) substrate by dc magnetron sputtering deposition. The surface roughness and X-ray diffraction spectrum of each film were measured by atomic force microscopy and X-ray diffraction, respectively. We concluded that the increase in carbon concentration suppresses the crystallization of platinum and causes the surface roughness to decrease.

Abstract: The authors developed a new nitriding process to form an aluminum nitride film on a pure aluminum surface. In this study, a rotary barrel polishing method was applied to gas nitriding in an attempt to form an aluminum nitride film on the surface of Al-Mg alloys. Nitriding was carried out at 823 K, 853 K, and 873 K for 3.6 ks to 25.2 ks. Alumina- and aluminum - 50mass% magnesium powders were used as the media that flowed in the barrel tank. An aluminum nitride film was formed on the aluminum alloy surfaces within a relatively short time. The effect of the treatment temperature on the formation and growth of the aluminum nitride was investigated. It was found that the formation and growth of the aluminum nitride film were greatly affected by differences in the Mg content in the aluminum substrate and by the treatment temperature.

Abstract: With the improvement of accuracy in machine tools, ultra precision final machining has been carried out by cutting instead of grinding. In addition, JIS method for cutting fluids is revised in order to consider earth environment. However, it is very difficult for workshop to extract an optimum machining condition. The results of this study contribute to extraction of an eco-friendly machining method and reduction of running cost as well as the excellent surface integrity. This time, final machining for high chromium cast iron as the turbocharger parts of the automobile was taken up as an example which acquired the good finished surface by cutting. Namely, for the purpose of reducing the running cost, instead of honing that has been used for finishing it in the hole processing, reaming was carried out for finishing, and its practicability was investigated experimentally. As a result, it was clarified that the surface integrity was improved with the oil hole reamer and the synthetic soluble oil.

Abstract: In cutting of aluminum alloys, one of the most serious problems is chip adhesion to cutting tool surface, often leading to tool failure, above all, in dry cutting. To address this problem, we adopted surface engineering approach, namely, a functionalization of tool surfaces by textures. In our previous research, we have developed the DLC-coated cutting tool with nano/micro-textured surfaces and the cutting tool with micro stripe textured surface formed using femtosecond laser technology. Face-milling experiments on aluminum alloys showed that the nano/micro-textured surface suppresses the genesis of adhesion at the atomic level. On the other hand, it was found that micro stripe texture prevents chip adhesion from growing larger even in dry cutting conditions. In this study, a cutting tool with new textured surface combined nano/micro texture and micro stripe texture was developed in order to further improve anti-adhesiveness in cutting of aluminum alloys. As a result, it was confirmed that the combined texture brings excellent anti-adhesion compared to the previously developed tools.