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野田 修平, 塩田 俊雄, 旗手 稔
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Many kinds of Al-5Zn-2Mg-2Cu sintered alloys were produced with modifying variously such fabrication conditions as preforming pressure, temperature and time of sintering and age-hardening-treatment. And then, the optimum fabrication conditions were obtained from the viewpoints of mechanical properties. Furthermore, increasing of its mechanical properties was attempted by modifying contents of Zn, Mg and Cu. As the result, a high tensile and high elongation alloy with 654 MPa in tensile strength and 12.5 % in elongation could be produced in the alloying ratio of Al-9Zn-3Mg-2Cu.
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木田 勝之, 藤居 拓也, 北村 和久, 山川 耕志郎, 木澤 克彦, 小林 秀敏
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Balls rotate during the rolling contact fatigue so that they are not affected by contact stress alone which occurs around the contact area. In our previous work, we found that the tensile stress occurring around the equator of the ball caused fatigue of the ball itself. Four groups of pre-cracks, whose surface lengths were 140μm, 220μm, 550μm and 700μm, were initiated on ball surfaces and the strength of these pre-cracked balls was measured. The static strengths and fatigue limits of all pre-cracked balls decreased with crack sizes. We concluded that the fatigue caused by a pre-crack located on the equator of the ball surface was important for understanding fatigue of silicon nitride balls. In our present work, carrying out fatigue tests of pre-cracked balls with 220μm cracks at three frequencies (5Hz, 20Hz and 35Hz) we found that the frequency had effect on speeds of the crack growths.
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土谷 邦彦, 河村 弘, 田中 知
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Lithium titanate (Li_2Ti0_3) pebbles are considered to be a candidate material of the tritium breeders for fusion reactor from viewpoints of good tritium recovery, chemical stability, etc. The pebbles of 0.3-2mm in diameter have been fabricated by a wet process, and characterization such as chemical property, tritium release property, mechanical property and so on have been performed. Especially, mechanical properties such as compressive strength are necessary for the design of fusion blanket packing the small pebbles. In this study, collapse loads of Li_2Ti0_3 pebbles with different diameters were measured by an unconfined compression tester, and contact strength of these pebbles was evaluated by Hertzian contact theory.
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山川 耕志郎, 木澤 克彦, 小熊 規泰, 木田 勝之
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It is important to investigate subsurface defects because they have a detrimental effect on the flaking failures occurring under rolling contact fatigue. In order to discuss the lives of bearings we need to investigate the relation between the defects and internal stress distribution in terms of mechanics. In this study, we calculated stress distributions around single inclusion and a pore using 3-D finite element analysis. When comparing the features of the pore and two kinds of inclusions we found that the stress concentration around the pore was extremely large and its effective volume, which is a size of the area affected by the concentration, was largest. However, outside the area whose distance is 2.3a (a: pore radius) from the center of the pore (or inclusion), there were no differences in stress distribution.
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栄 中, 井堰 充洋, 矢野 泰隆, 森田 健敬, 久保田 祐信, 近藤 良之
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Two-roller rolling-sliding contact fatigue tests are performed to evaluate the rolling contact fatigue strength of materials. Crowned rollers are sometimes used to achieve the high contact pressure and/or to avoid scoring. In this case, the change in the configuration of contact surface due to wear usually causes the change in contact pressure distribution. It makes the rolling contact fatigue strength evaluation difficult. In the present study, the relationship between the rolling contact fatigue strength and the contact pressure distribution at the end of test were examined by rolling contact fatigue tests and finite element analyses. Consequently, it was found that the position of the crack initiation coincides with that of the maximum contact pressure at the end of test and that the crack growth life would be related to the value of the maximum contact pressure.
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岩佐 正明
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The fracture strength of GFRP/stainless-steel adhesive joints reinforced with glass mat was studied analytically and experimentally. First, the stress distributions near the bonding edge were analyzed with FEM. The FEM results showed that the shear stress and the normal stress distributions near the bonding edge can be expressed by two stress singularity parameters. Second, to measure the delamination initiation load, tensile shear tests were conducted on taper lap joints and those reinforced with glass mat. The experimental results showed that the delamination strength of taper lap joints reinforced with glass mat can be evaluated with stress singularity parameters, and reinforcing the bonding edge with glass mat effectively enhanced adhesive joint strength.
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小泉 賢祐, 磯野 宏秋, 杉林 俊雄, 井形 直弘
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川島 分華, 八田 博志, 塩田 一路
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Carbon fiber reinforced carbon matrix composites, C/Cs, process excellent high temperature capability, but have the deficit of weakness against high temperature oxidation. Thus, C/Cs are generally used with an anti-oxidation coating, for which silicon carbide, SiC, is frequently used. However, the SiC coating is slowly but gradually oxidized. The purpose of the present study is to develop a sensor, which can detect oxidation rates at severe high temperature environments. The sensor under discussion is composed of SiC/C multi-layered coating formed on a substrate and can measure the electric resistance of the multi-layered coating. In this paper, it is shown that this sensor has capability of in-situ monitoring of oxidation rates of SiC coating up to temperatures of 1800K.
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小山 昌志, 八田 博志, 石井 考佑, 福田 博
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In order to apply Carbon/Carbon composites (C/Cs) to various hot structures, a secondary bonding technique effective at elevated temperatures is frequently required. In the present study, carbon and SiC bondings between C/Cs were formed, and strengths of the bondings were evaluated at elevated temperatures up to 2273K in vacuum using the double-notched shear method. The results revealed that bonding strengths became higher than the inter-laminar shear strength of the substrate C/C when the bonding layer was thin, and bonding strengths increased with increasing temperature. The enhancement of carbon bonding with temperature were shown to be caused mainly by the evaporation of absorbed water up to a temperature of 1800 K with a slight additional effect of residual thermal stress. It was also shown that heat treatment at higher temperature than the processing temperature made the bonding stronger.
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安藤 柱, 斧 督久, 李 相起, 中尾 航, 高橋 宏治
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Mullite admixed with SiC particle were sintered for aim to attach with crack-healing ability. The effects of the crack-healing treatment on the structural integrity and reliability of machined components were investigated. The nominal bending strength of as-received specimens and heat-treated specimens at room temperature were investigated. As the result, by using crack-healing, the bending strength of machined specimens was increased about 50%〜130%. Local fracture strength was assumed to recover completely, and the cracks formed by machining were healed completely. A large self-crack-healing ability is desirable for obtaining a higher structural integrity in ceramic components.
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手塚 俊文, 安野 拓也, 向後 保雄
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The effects of heat treatment on fiber/matrix interface morphology of carbon fiber-reinforced carbon matrix composites ( C/C composites ) were examined. In addition to fiber/matrix interface morphology, the fiber efficiencies of C/C composites and the tensile strength were determined as a function of heat treatment temperature. The fiber efficiency and the tensile strength was found to decrease with increasing heat treatment temperature. The observations of fiber/matrix interface by using SEM suggested that the microcracks and the fine voids existed at fiber/matrix interface. Since the bonding strength of the fiber/matrix interface lowered by these defects, the tensile strength of C/C composites decreased.
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荻原 慎二
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An elastoplastic shear-lag analysis is developed to analyze the stress distribution around a fiber break in a composite to consider the plastic deformation in the matrix. One-dimensional shear-lag analysis which consider the fiber, the matrix and the interphase shear layer is conducted. It is assumed that the fiber consists of an elastic material and the matrix and the interphase shear layer elastoplastic materials. The method of successive elastic solutions is used to determine the plastic strain distribution in the elastoplastic materials.
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小柳 潤, 山崎 将史, 川田 宏之
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Interfacial debonding propagation is very important problem for long-term creep in unidirectional composites because material's properties of the unidirectional composite decrease with increase of the interfacial debonding length. In this study, time-dependent interfacial failure was investigated by using the Raman Micro Spectroscopy. The specimen was single fiber conposite consisting one carbon fiber embedded in the vinylester resin and it was subjected to constant strain condition to assume the long-term creep in the unidirectional composites. The interlace between the carbon fiber and the vinylester resin is relatively weak; therefore interfacial frictional stresiss is one of the most important factors, which dominated the interfacial debonding propagation. In this paper, the compression stress applied to the interface in the direction of fiber rudius direction is calculated as a function of time on the consideration of Poisson compression and thermal residual stress. The interfacial frictional stress is assumed to be dominated by the Coulomb's friction and compared with the Experimental results. The interfacial debonding propagation is discussed by using the relaxation of the frictional stress. Long-term behavior of the interfacial debonding propagation is predicted in the single fiba composites.
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永田 雄介, 和田 明浩
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In this study, debonded particles in a random participate composite are analyzed by three-dimensional finite element method to investigate their load carrying capacities, and the way to replace a debonded particle with an equivalent particle is examined. The variation in Young's modulus and Poisson's ratio of a damaged composite with the increase of the debonded angle was evaluated for different particle arrangements, which in turn compared with the results by equivalent inclusion method. Consequently, it was found that by replacing a debonded particle with an equivalent orthotropic particle, the macroscopic behavior of the damaged composite can be reproduced so long as the interaction between neighboring particles is negligible.
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吉村 彰記, 武田 展雄
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The internal damage process of carbon fiber stitched carbon fiber reinforced plastic composite laminates was investigated through both experimental observation and numerical analysis. The damage process of the stitched laminate was compared with that of the unstitched one. From the experimental observation results, it was shown that delamination was suppressed by the stitch threads, but the ultimate strength was lower due to the stitching. A finite element analysis was carried out in order to explain the experimental features. A novel FE model was proposed, where the internal damage was modeled by using specially developed elements. By analyzing this model, it was made clear that the reason of the suppression of the delamination was that stitch threads suppressed the mode-I deformation of the delaminated layers.
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市村 純, 早川 栄二, 中田 政之, 宮野 靖, 金原 勲
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平井 悠斗, 丸山 勇哉, 宗宮 詮
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It is known that a mechanical property will change because a crystalline polymer adjusts a crystal region. It is important to grasp about the viscoelastic property for a long-term reliability. Then, this research examined the creep behavior using the polyamide resin and glass fiber reinforced polyamide which the various degrees of crystallization adjusted by the three point bending creep test. As a result, crystallinity increases with heat treatment temperature, and it develop that crystallinity can be artificially adjusted. Then bending creep behavior was suppressed with crystallinity increasing, and this tendency was significant at longer test time. And superposion low of Arrhenius type of time-temperature formed, and master curve of creep compliance curves could be made.
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川節 望, 青木 清隆, 田北 勝彦, 加藤 英司
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Due to considerations for lighter weight, recent years have seen rapidly expanding use of FRP materials in large structures. FRP blades for wind turbines are an example, with blade length of over 30m and maximum blade thickness of over 100mm for lOOOkw class equipment. Thus far, however, there have been no proposals of non-destructive test methods for the quantitative evaluation of the internal state of FRP in materials having thickness of over 50mm. Although ultrasound inspection is often used for thick board FRP, this method does not allow accurate, quantitative detection of internal defects. This paper presents a non-destructive testing method that employs low frequency ultrasound defect detection technology, developed as an inspection technique for the quantitative evaluation of internal defects in thick board FRP material.
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松井 健, 大塚 年久, 田村 宏, 小林 志好
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It is necessary to get a fundamental data of FW・RP cylinder setting up a side circular hole for design of mechanical structures transmitting torsion load. In this study, the torsion rigidities near the side hole were measured by static torsion tests. Moreover, the properties of FW・RP cylinder with a side hole were calculated by original FEM program that is able to simulate FW・RP cylinder. As a result, it is concluded that each of stress distribution and each of Normalized stress σ_u/σ_s has closely relation with each of the following parameters, (1) Fiber orientation rlivArtinn : θ, (2) Daimeter of a side circular hole: a.
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徳平 初月, 小林 康男, 石川 圭介
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We conducted the compression tests on the flexible polyurethane foam and flexible foarn, to understand the compression characteristics. The cell structures were also observed with the scanning electron microscope (SEM). We found the difference in the compression behavior for the repetive foams. The maximum stress was proportional to the compression rate. The harder foam had the smaller cell.
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加治 岳士, 宇野 隆, 合田 公一, 大木 順司
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For the purpose of improving the toughness of natural fiber green composites, mercerization was applied for ramie fibers. Mercerization, i.e. alkali treatment to single-fibers and fiber bundles of ramie, was carried out by NaOH solution, and the biodegradable resin matrix composite using the mercerized fiber bundles was press-formed. The results of tensile test showed that both the mercerized single-fibers and bundles were improved in tensile strength slightly higher than the untreated fibers, while fracture strains of the mercerized single-fibers and bundles increased to 0.066 and 0.060, respectively, i.e. approximately twice higher than those of the untreated fibers. From such a change in fracture strain, the composite using the mercerized fiber bundles was largely improved in plastic deformation function.
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鈴木 浩治, 合田 公一, 金原 勲
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川節 望, 新藤 健太郎, 田北 勝彦, 加藤 英司
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Vacuum assisted resin transfer molding (VaRTM), allowing the forming of low cost and relatively high quality structures, is widely used for the fabrication of wind turbine blades and other large FRP structures. In the VaRTM method, a dry fabric laminate structure is impregnated with resin on the surface of the dry perform. Accordingly, substantial time is required for the resin to fully occupy thick portions of the item being formed, thus complicating efforts to uphold the stability of manufacturing steps. In order to achieve high quality molding in a short time, molding conditions such as the arrangement of resin injection ports must be optimized, making it essential to accurately grasp the behavior of resin impregnation behavior. With the objective of ascertaining the impregnation behavior of resin, this report presents measurement results for the edge positioning of resin flow in the VaRTM method applied to thick CFRP, as well as time-wise changes in resin pressure.
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川節 望, 後藤 充成, 古閑 正憲, 田北 勝彦, 戸島 学
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Fiber reinforced plastic (FRP) features a specific gravity approximately one quarter of that of steel material, as well as superior corrosion resistance, and is therefore promising in terms of applications in high speed rotary equipment and other machinery. Although the rotor blades of large axial flow fans utilized in thermal power plants have conventionally been made of metal, the use of FRP would enable lighter weight and greater resistance to corrosion. In turn, this could allow reduction in size and longer life for moving and sliding parts, as well as lower maintenance costs. This paper presents the results of material and pilot plant tests of FRP rotor blades developed for use in axial flow fans.
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高久 泰弘, 小林 康男, 石川 圭介
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We experimented creep tests for polyetherethylene(PEEK) and polyetherimide(PEI) and polyoxymethylene(POM) at constant applied stress. The creep curves of PEEK and POM depended on the temperature and applied stress. The lives of the polymers were expressed by the following equation. The values of n depend on the temperature. They were reduced at high temperatures.
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堺 達紀, 宗宮 詮
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It is important to discuss the effect of water absorption about Polybutylene Succinate (PBS), one of Biodegradable plastics. In this study, PBS resin was immersed in pure water at each temperatures, 25, 35 and 50℃ and the change of mechanical properties were discussed. Water absorption rate at each temperatures followed Pick's diffusion law at an early stage. In addition, bending strength and elastic modulus went down because of water absorption. As a result of FT-IR analysis, it was found that hydrolytic degradation was caused by water absorption with passage of immersion time. The strength dropped drastically and the brittle fracture was caused after hydrolytic degradation occurred to some extent. This is because voids were generated within the resin by the degradation and they were leaded to cracks.
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北村 佳之, 松雄 晃, 合田 公一, 大木 順司, 友永 文昭
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The purpose of this study is to apply bamboo fibers and powders to resin matrix composites, in order to reduce use of glass fibers which are often pointed out from the viewpoint of environmental impact. Injection molding method was used for fabrication of the composites. The result showed that relatively long short-fibers are not adequate in filling injection molding die, while compounds using small length of short-fibers can fill it well. Especially bamboo powders can be included up to 50wt% in the composite. Alkali-treated bamboo powders are quite useful in increasing the tensile strength of a biodegradable resin matrix composite in comparison with untreated bamboo powders, while the former powders are not so effective in increasing the tensile strength of a polypropylene matrix composite. The biodegradable resin matrix composite including 50wt% bamboo powders is clearly higher in strength than the biodegradable resin matrix composite including 20wt% fibers and the polypropylene matrix composite including 1Owt% fibers.
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高木 均, A. N. Netravali
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Environmentally friendly "Green" composites were fabricated from a natural cellulosic fiber (MAO fiber) and a biodegradable starch-based resin through hot pressing. The effects of fiber length and alkali surface treatment on mechanical properties of composites were investigated. Fiber lengths of 2.5, 5, 10, and 15 mm were used and fiber weight content was adjusted to 56%, to obtain short fiber composites with random orientation. Ultimate tensile strength increased with increasing the fiber length up to 10 mm and remained almost constant for further increases in fiber length. Fracture strain for the composites fabricated with fiber length of 2.5 mm showed the smallest value of approximately 2%, which is less than that of MAO fiber. This might be attributed to the debonding at the fiber/matrix interface.
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宮下 幸雄, 長谷川 広尊, 茂木 征史, 武藤 睦治
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In order to develop a new laser cutting method for brittle materials, thermal stress analysis and cutting experiment of glass were carried out. Crack was propagated by the local thermal stress generated by laser irradiation. However, crack didn't follow the scanning line of laser when the scanning direction changed. FEM (Finite Element Method) analysis was carried out to predict the crack growth behavior. The result shows that the crack growth behavior obtained by FEM analysis agrees with the experimental result. Twin beam technique was studied by FEM analysis to control the crack growth direction. For twin beam located in parallel to the laser scanning direction, crack growth direction can be controlled by changing the intensity ratio between the two beams.
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吉良 章夫, 友重 竜一, 濱嶋 英樹, 伊東 繁, 藤田 昌大
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A method to generate an extremely high impulsive pressure using a converging metal jet has been developed. The metal jets are discharged from the collision points, when a metal plate is accelerated by the detonation of an explosive and collides with a conical concave metal block. The metal jets discharged on the concentric circle of the conical concave fly toward the center while converging and collide on the central axis, and the collided metal jets exhibit the extremely high pressure. In the present investigation, framing photographs were taken using an image converter camera to investigate the phenomenon occurred in the generator. The photographs show that the metal jets are discharged from the collision points between the metal plate and conical concave block, and then, collided at the central axis. The maximum pressure obtained under vacuum was estimated about 0.83 TPa from the velocity calculated from the photographs, and the results were slightly lower than that evaluated theoretically.
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濱田 亨, 中村 雄一, 伊東 繁
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As a new method of generating the overdriven detonation, the concentric double cylindrical high explosive was developed. From the results of a numerical analysis, a measurement of a detonation velocity and a detonation pressure, it has been inferred that the detonation velocity and the detonation pressure was about two times higher than that of the Chapman-Jouguet state. In this investigation, as a application which used the super high energy obtained by the overdriven detonation, the experiment of the shock consolidation of a metallic powder was done. A metallic powder used the tungsten carbide with high hardness and a high melting point. As a result of the shock consolidation experiment, the tungsten carbide had been solidified though the crack was slightly generated. From the condition of Prummer and Meyers, it was inferred that the shock pressure that was more than 21GPa was load with the tungsten carbide powder. The effectiveness of the concentric double cylindrical high explosive could be also shown for the shock consolidation system in this investigation.
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大塚 誠彦, 飛田 栄治, 黒木 賢二, 伊東 繁
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The wire explosion technique generates plane shock wave by exploding parallel metal wire rows, using a shock large current. In this study, we investigated underwater shock wave generated from four kinds of metal wires (copper, alumel, SUS304, nichrome) using the shadowgraph method and a high-speed camera (IMACON 468 of HADLAND PHOTONICS, interframe times 10ns to 1ms in 10ns steps independently variable number of channels framing:4 streak:1). The explosion power of a metal wire showed a good relation to its rate of electric resistance. It seems that a strong shock wave is obtained, if the bold wire using a mass condenser bank is exploded.
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坂本 英俊, 河邉 真二郎, 佐藤 和幸, 姫野 政弘, 伊東 繁
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銘苅 春榮, 福本 功, 柴田 信一
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発行日: 2004/11/05
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The present paper refers to experimental study of the powder mixture of wood charcoal, iron and copper followed by spark plasma sintering. A composite molding technique is applied to the compression molding of different type of powders at a constant heating temperature and forming pressure. The main factors affecting the sintering and bonding of different substances include temperature and pressure. It was found that Fe/Cu/Carbon powders can be heated fast and sintered in very short time: ISminutes at the temperature range of 820℃ to 990℃ using spark plasma sintering. The investigation on manufacturing of functionally composite materials is summarized above and it is evident that more work using different approaches is necessary.
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中山 清光, 福本 功, 銘苅 春榮
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発行日: 2004/11/05
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Composite material using sludge and aluminum powders have been fabricated by spark plasma sintering method. The optical forming conditions were investigated in terms of mechanical property. As a result, it was found that the factor of sludge amount mainly affect on the bending strength. Adding the sludge amount 2% to aluminum powders, the bending strength of composite material increased drastically than aluminum material. From the observation of crack elongation with photomicrograph, it was obvious that the sludge agglomerated powder play the role of obstruct elongation of crack.
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田中 茂, 李 政錫, 外本 和幸
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発行日: 2004/11/05
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Al-based composites are tried to be fabricated using dynamic compaction of powders compressed through underwater shock wave. Some composites, Al-carbon short fiber , Al-SiCp, Al-diamond, are successfully recovered and fully densified without cracks, and some of the composites showed high hardness and ductility through bending tests.
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外本 和幸, 李 政錫, 李 尚勲, 藤田 昌大
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発行日: 2004/11/05
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A method for the coating of thin layer compressed by underwater shock wave in obtaining compacted layer and synthesized intermetallic layer through reaction is proposed in the present investigation. The layers recovered was characterized and the possibility of such dynamic process is discussed.
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濱嶋 英樹, 徳永 泰子, 川野 和央, 伊東 繁
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The characteristic values of the detonation waves, such as detonation pressure, temperature etc., for a particular explosive is generally constant and cannot be modified. An attempt has been made to attain a high pressure on a pressurized single high explosive. The generated pressure that was more than the C-J pressure was examined by Manganin gauge, optical observation and numerical simulation. The numerical results were validated using experimental results.
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日向 毅, 井山 裕文, 伊東 繁
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発行日: 2004/11/05
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The explosive forming method is one of the material processing methods. In this method, the shock wave generated by the explosion and propagated through a suitable pressure medium like as a water or air act on a metal plate, a metal tube, etc. It gives a very high strain deformation of the material and finally a suitable plastic deformation. This method is called as a shock bulge forming. The advantages of this method are hard to produce the spring back and a high strain rate material processing. The predominance of shock bulge forming is investigated by comparing with static press bulge forming, hi case of the explosive forming method, the strain and the bulge depth of the aluminum base alloy plate were almost same as the steel plate experimental results obtained by the static press method.
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岡川 啓悟, 相沢 友勝, 進藤 康人, 谷所 慎二, 宮城 由行
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発行日: 2004/11/05
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This paper describes a lap welding technique for aluminum sheets with a gap (before welding) and its experimental results. When a high-density magnetic flux is suddenly generated inside a flat one-turn coil, eddy currents are induced in the overlapped ends of two aluminum sheets (thickness 1.0 mm each) placed inside the coil. As a result, an electromagnetic force acts on the two sheets and presses them together so that they collide with each other. If the moving velocity of the two sheets is high, the collided surfaces can be cleared by an effect of the collision that is known as explosive welding, and then can be joined both by the electromagnetic force on them and by the joule heat generated in them. A bank energy required for this lap seam welding of an area 5x50 mm^2 is less than 1 kJ.
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相沢 友勝, 岡川 啓悟, 熊谷 正樹
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発行日: 2004/11/05
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This paper describes a new seam welding technique and its experimental results. When an impulse current from an energy-storage capacitor bank passes through a flat one-turn coil, a high-density magnetic flux is suddenly generated around the coil. Eddy currents are induced inside the overlapped ends of two sheets of various Aluminum alloy (thickness 1 mm) placed outside the coil. The sheets have a gap between them. The ends can be joined both by the Joule heat generated in them and by the impact effect with pulsed magnetic pressure applied to them from one side. Bank energies required for seam welding an area 5x100 mm^2 are less than 1.3 kJ for A1050 sheets and 3.5 kJ for A5182 sheets, respectively.
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森 昭寿, 外本 和幸, 藤田 昌大
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発行日: 2004/11/05
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This paper proposes the method to control the underwater shock wave and its application in explosive welding. A high-explosive is made to incline at a certain angle in order to decrease the horizontal collision point velocity, which is one of the important parameters that should be satisfied in explosive welding using underwater shock wave. When the constant-thickness explosive is used, the welding conditions change with horizontal position from the detonation side to the other side. Then, the method of linearly increasing the thickness of explosive from the detonation side so that the same welding conditions can be attained is applied. The results of numerical analysis about these methods respectively are reported and compared with the experimental ones.
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白本 和正, 森 昭寿, 外本 和正, 藤田 昌大
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発行日: 2004/11/05
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A new method of explosive welding is proposed. In the new method, an explosive put on a block of the thick steel is set on the one side of the specimen. The whole set-up is submerged in the water. When the explosive is detonated, underwater shock wave moves on the flyer plate from the near side to explosive to the far side. The shock wave hold a very high pressure, so that the flyer plate is abruptly accelerated by pressure action and collides with a suitable velocity to the base plate a slightly apart from the flyer plate. Thus explosive welding is achieved. Shock pressure decays with the distance from the explosive. To make up the energy loss of shock wave, a reflector of thick plate is covered the passage of shock wave. To obtain an available reflection effect, the reflection is inclined to the bottom plate.
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Azhari SASTRANEGARA, 足立 忠晴, 荒木 稚子, 山路 昭彦
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発行日: 2004/11/05
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The effect of transverse impact on buckling behavior of a column under axial impact loading is numerically investigated by finite element analysis. A column under an axial impact was subjected to a transverse impact to reduce its structural stiffness instantaneously. The transverse impact generates buckling with low critical load and improves energy absorption. The transverse impact has a significant effect on inducing plastic buckling. The results show that the transverse impact applied almost simultaneously with axial impact gives highest energy absorption. The simulation results prove the experimental ones qualitatively and show that the energy absorption of column is improved without reducing column stiffness beforehand.
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松本 悟志, 中村 裕一, 伊東 繁
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発行日: 2004/11/05
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We make a new SPH (Smoothed Particle Hydrodynamics) code based on MLS (Moving Least Squares) method to analyze the dynamics of stress wave. The new code is examined by the simulation of an elastic wave interacted with a free surface. The result using the new code is compared with both the result of SPH and the experimental results of the model blasting using the electric detonator. The elastic wave emanates from the charge hole and interacts with the free surface. Propagation of elastic wave and reflection at the free surface are well simulated by the new method compared with SPH method.
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徳永 仁夫, 梅津 浩一, 池田 清彦
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発行日: 2004/11/05
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The thermally tempered glass has strong resistance for the surface crack, because the residual compressive stress exists near the surface of the glass. However, it also has the residual tensile stress in the center of the glass. Crack propagation of the thermally tempered glass depends on the distribution of the residual stress. We examined the crack velocity of the tempered glass using the Extended Distinct Element Method (EDEM). From numerical results for the normal glass and tempered glass, it is confirmed that the crack velocity depends on the stress gradient.
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岩堀 豊, 石川 隆司
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発行日: 2004/11/05
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Composite materials, especially CF/epoxy 2-D laminates, have the capability of light weight design for in-plane high loading structures. On the other hand, interlaminar strength is not strong against a through-the-thickness direction load. The authors' group carried out an evaluation of interlaminar strength improved CFRP laminates which are reinforced by through-the-thickness fiber, such as Kevlar or carbon stitching and also Z-anchor^<TM> which technology is developed by Shikibo, Ltd. and Mffl, Ltd. This paper introduces the interlaminer strength improvement effects on CFRP laminates such as mode I energy release late of Gi for CF stitched CFRP laminates, impact damage propagation, and compression after impact (CAI) strength.
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庄山 直芳, 関根 政直, 藤本 浩司, 塩谷 義
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発行日: 2004/11/05
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Split Hopkinson Pressure Bar (SHPB) is known as a simple method to investigate the deformation of materials at high strain rate. In the case when the specimen is not short, the result is inaccurate because of the assumption of existing evaluation method that the specimen has sufficiently short length. This paper introduces a new evaluation method utilizing Fourier analysis which enables accurate investigation of viscoelastisity of materials considering the stress and the temperature distribution in a long specimen. The attenuation of silicon nitride, at high temperature from 900℃ to 1300℃ and at high strain rate in frequency around 4kHz, was obtained with this method.
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楳田 努, 梅木 英男, 三村 耕司
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発行日: 2004/11/05
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The measurement accuracy of dynamic material testing is required for the development of design and numerical simulation based on the accurate model of stress-strain relation which is applicable to various strain-rate conditions. On the other hand, the Hopkinson bar method (HBM) is the most widely used one for the dynamic compression test, whereas the method is not used very much for the dynamic tension test. The non-coaxial Hopkinson bar method (NCHBM) is one of the recently proposed dynamic tension tests and is based on HBM. In this study, the accuracy of the stress-strain relation obtained on the basis of NCHBM is examined by using the FEM code LS-DYNA. The effects of the rising time of applied velocity, the size and geometry of specimen, the boundary condition, and so forth are also examined.
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板橋 正章, 福田 博, 中島 茂
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発行日: 2004/11/05
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After unexpected failure, the fractured material surface will be investigated with SEM (scanning electron microscope) to find the cause of the failure. In this paper, we tried to distinguish the loading histories of the dynamically fractured 6061-T6 aluminum alloy by observing the side surface with SEM. The alloy was fractured by dynamic tension (ε=l×10^3s^<-1>) with and without low-cycle pre-fatigue. On the side surface of the specimen, neighboring fractured surface, relatively large cracks bigger than, for example, lOμm were existed. The number of cracks and the size of them were evaluated quantitatively. The number of the relatively large cracks for the pre-fatigued specimens is greater than that for the virgin specimens.
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