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| 1.
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千徳, 英介 ; 上田, 隆司 ; 山田, 啓司 ; 細川, 晃
概要:
Laser forming of a sheet metal is the bending process caused by the thermal stresses which is produced in the sheet by l
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aser irradiation. Therefore, the temperature distribution in the sheet irradiated with laser beam is one of important factors to determine the bending angle of the sheet. In this study, the influence of temperature distribution and the experimental conditions like the diameter of laser beam and the thickness of a sheet on the bending angle is investigated experimentally. The temperatures of a surface irradiated with CO2 laser and its opposite surface are measured using an infrared radiation pyrometer with an optical fiber. As a result, the bending angle is directly proportional to the temperature Ts at the sheet surface irradiated with laser beam and the beam diameter D, and inversely proportional to the thickness h of the sheet. A parameter indicated by D1.41Ts1.5/h1.7 has high correlation with the all bending angles obtained under various experimental conditions. 様々な加工条件で板材のフォーミング加工を行い, 同時にレーザ照射部表面および裏面温度を測定し, 加工条件と照射温度の変形角への影響を調べた. その結果, 変形角はレーザビーム径の1.4乗に比例し, 照射温度の1.5乗に比例し, 加工物の板厚の1.7乗に反比例しており, これらの結果より導出した式は定性的に加工条件の変形角への影響を良く表している.
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| 2.
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上田, 隆司 ; 山田, 啓司 ; 及川, 志郎 ; 細川, 晃
概要:
Laser forming is the thermal process to deform a metal plate using the thermal stress produced by the rapid heating with the laser. In this study, the influence of irradiating conditions of CO2 laser on the bending angle of the
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workpiece is investigated. The temperature at the back surface of the workpiece irradiated with CO2 laser is measured using a two-color pyrometer with an optical fiber. The temperature distribution in the workpiece is calculated using the FEM thermal analysis. Simple bending experiments with one-way laser scanning are carried out. Stainless steel SUS304 of various thickness is used as work material. The results obtained are as follows. The bending angle is proportional to the temperature of the workpiece irradiated. The temperature of workpiece increases with the increase of laser power, the decrease of feed rate of the laser beam and the decrease of plate thickness. After all, the bending angle becomes larger with the increase of laser power, the decrease of the feed rate and the decrease of the thickness of the plate. The temperature of the workpiece can be used as a signal to control the deformation of the workpiece.
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| 3.
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上田, 隆司 ; 佐藤, 昌彦 ; 杉田, 忠彰
概要:
Temperature of interface between a cutting tool and a workpiece is measured using two-color pyrometer with a fused fiber
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coupler. A conical tool is used as the cutting tool which is made of translucent alumina sintered under HIP, and 0.55% carbon steel is used as a workpiece. The infrared rays radiated from the interface and transmitted through the conical tool are accepted by a fused fiber coupler and led to two infrared detectors of different spectral sensitivity. Temperature is obtained by calculating the ratio of the output voltage from these two detectors. The results obtained are as follows. The temperature increases very rapidly and reaches 1000°C at about 40 μs after the beginning of cutting. The rate of increase of temperature is very great : about 108 °C/s at the cutting speed of 1 500 m/min. The temperature increases with the increase of cutting speed, but at a speed faster than 1000 m/min its influence is small. The temperature shows a tendency to saturate about 1300-1400°C as the cutting speed increases.
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| 4.
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山田, 啓司 ; 大礒, 桂一 ; 細川, 晃 ; 上田, 隆司
概要:
The thermal stress cleaving of silicon wafer with a laser beam is a prospective technique, which supersedes the mechanical dicing. This method makes it possible to cut a wafer at very high production rate in comparison with the diamond thin
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blade wheel and to protect the wafer from the contamination of cutting coolant and chips. In this paper, the cleaving mechanism of silicon wafer irradiated with the pulsed Nd:YAG laser is investigated. The temperature at the area irradiated with laser is measured using two-color pyrometer with an optical fiber. The acoustic emission is also measured to examine the mechanism of the crack propagation. In the process, the temperature at the area irradiated with laser should be controlled in order to reduce the thermal damages and to improve the cleaving accuracy.
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山田, 啓司 ; 小谷, 祐司 ; 上田, 隆司
概要:
The temperature of workpiece irradiated with CO2 laser is measured using a new type of infrared radiation pyrometer with an optical fiber. In the pyrometer, a chalcogenide optical fiber and a two-color detector which consists of InSb and
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InAs detector are used. The power intensity of the laser beam during the exposure time and the two dimensional picture of the intensity distribution of the laser beam are measured experimentally. The measuring system for the intensity distribution of laser beam consists of MCT cell and an optical fiber. The temperature distribution on the workpiece irradiated with laser is calculated numerically using FEM for unsteady state. The change of physical properties of materials is considered. Comparing the experimental results with the calculated ones, the absorptivity of the work material for CO2 laser is obtained.
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| 6.
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上田, 隆司 ; 山田, 啓司 ; 古本, 達明
概要:
The flash temperature of a dental hard tissue irradiated with pulsed Nd:YAG laser is measured using a two-color pyromete
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r with an optical fiber. This pyrometer consists of a chalcogenide optical fiber and a laminated infrared detector. The influence of the laser power on the temperature of the dental tissue is investigated, and the relationship between the laser power and the removal volume of the dental tissue is obtained. In order to examine the thermal damage on the dental tissue, hardness and bending strength of the tissue are measured after being heated electrically at various temperatures. FEM thermal analysis is conducted to estimate the temperature distribution in a teeth and to discuss the influence of heat flux on the dental pulp. The results obtained are as follows. The appearance of the tissue begins to change at about 150°C and its hardness decreases with the increase of temperature. Its bending strength starts to decrease at about 50°C. Only the carious tissue can be removed from the cavity due to the large difference of energy absorptivity between the tissue and the carious one. It is possible to protect the dental pulp from thermal damage, because the temperature gradient in the teeth is very steep due to the small thermal conductivity of the dental tissue.
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| 7.
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Al Huda, Mahfudz ; 山田, 啓司 ; 上田, 隆司
概要:
The temperature of the flank side of the cutting tool edge that has large affect on machined surface integrity is measur
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ed using two-color pyrometer with a fused fiber coupler. The infrared rays radiated from the cutting tool edge are accepted by an optical fiber, and separated to two optical fibers at the fused fiber coupler. Each fiber leads the infrared ray, respectively, to two infrared detectors with different characteristic of spectral sensitivity. Temperature is obtained by calculating the ratio of the output voltage from these two detectors. A CBN tool (CBN content : 60 volume percent, density : 3000 kg/mm2) is used as the cutting tool. Annealed steel (S45C), bearing steel (SUJ2), and quenched steel (S55C) are used as the cutting materials to investigate their affect on the tool edge temperature. The results obtained are as follows : (1) The technique developed is suitable for measuring the temperature of the flank side of the cutting tool edge. (2) The temperature of the cutting tool edge is highly effected by cutting speed. (3) The temperature increases slightly with the increase of depth of cut and feed rate. (4) On the cutting of quenched steel which has the largest hardness among these three materials, the temperature is about 50°C higher than that on the bearing steel cutting, and the temperature of the annealed steel cutting is the lowest.
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| 8.
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佐藤, 昌彦 ; 上田, 隆司 ; 西田, 昌弘
概要:
Tool face temperature of single crystal diamond in high precision orthogonal cutting of aluminum and copper is measured
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using two-color pyrometer with an optical fiber. The infrared rays radiated from the chip-tool interface and transmitted through the diamond tool are accepted by an optical fiber and led to two-color detectors of different spectral sensitivity. Temperature distribution on the tool face is analyzed by employing finite element method and calculated results are applied to the estimation of the maximum temperature on the tool face. The results obtained are as follows; (1) The technique developed is suitable for measuring the tool face temperature in single crystal diamond cutting. (2) Output wave of temperature was clearly recorded. The tool face temperature measured is approximately 190°C for Al and approximately 220°C for Cu when cutting speed was about 620m/min. (3) The temperature increases with the increase of cutting speed. (4) The temperature on the tool face measured is in good agreement with that calculated.
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| 9.
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佐藤, 昌彦 ; 竹田, 陽一 ; 上田, 隆司
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