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Ryuji KOBAYASHI, Hideaki ITO, Tsutomu EZUMI, Susumu TAKAHASHI
Article type: Article
Pages
195-196
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Toshihisa NISHIOKA, Takehiro FUJIMOTO, Ryota NISHIOKA, Kousuke KURIO, ...
Article type: Article
Pages
197-198
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In previous studies, the authors have developed an intelligent hybrid experimental-numerical method based on a variational principle minimizing experimental measurement errors. In this study, the phase shifting method of moire-interferometry is used to clarify deformation behavior near an interfacial crack tip. In this experiment, the bimaterial specimen consists of epoxy and aluminum. Displacement distribution data for the intelligent hybrid method are obtained by the operation of image processing. The stress and strain distributions near the crack tip are visualized from the results of the intelligent hybrid method. Moreover, the higher-order information such as the separate J integral and the stress intensity factors are extracted.
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Jeonghwan Nam, Akira Shimamoto, Taku Shimomura
Article type: Article
Pages
199-200
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In this study, stress intensity factors were investigated and determined by caustics method and photoelastic experiment to clarify the behavior of a crack tip under various biaxiality ratios on the polycarbonate plate with isotropy and anisotropy used as structural components. As result, It was confirmed that only "K_I" affected without receiving the effect by biaxiality ratio, isotropy and anisotropy in case of the crack angle θ=0°under the biaxial loading. It was confirmed that an affects on only K_I in the isotropic polycarbonate plate with crack angle θ=45°under the biaxial load (1 : 1). However, it is proven that simultaneously affected the mode-I and mode-II in the biaxiality ratio is more than 1 : 1. Furthermore, The stress intensity factor value K_II was extremely to rise from over biaxiality ratios of 3.0 by extrusion direction and biaxiality ratio in case of polycarbonate plate with the anisotropy.
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Kenji MACHIDA, Kenji USUI, Takayoshi HIRANO
Article type: Article
Pages
201-202
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The displacement around the crack tip of homogeneous and dissimilar materials was measured by speckle photography. A CNS specimen was employed to measure the displacement under the various mixed-mode loading. The displacement data obtained by speckle photography were not as smooth as that obtained by the finite element analysis. A large error arose in the evaluation of stress-intensity factors from the raw displacement data. Therefore, the displacement data were smoothed by 2-D fast Fourier transform and the least squares method. Then, stress-intensity factors of asymptotic solution derived by Sun and Jih were evaluated using the displacement data obtained from speckle photography by the least squares method. The stress-strain field near the crack tip evaluated by using the asymptotic solution was in good agreement with that of finite element analysis.
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Yasuyuki MORITA, Shinichi SUZUKI
Article type: Article
Pages
203-204
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Opening displacement of a bifurcated notch is measured by means of Moire interferometry. The bifurcated notch has the same shape as a fast propagating crack just after bifurcation. Two branches of the bifurcated notch are symmetric and the angle between them is 27 degrees. The measurement results show that the opening displacement of the mother notch is proportional to the square root of distance r from the nominal tip of the mother notch. This result is in good agreement with that, after bifurcation of a fast propagating crack, crack opening displacement of the mother crack is proportional to the square root of distance r from the nominal tip of the mother crack.
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Shinichi SUZUKI, Yasuyuki MORITA
Article type: Article
Pages
205-206
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The stress field around a fast propagating crack is measured at 6.9μs after carck bifurcation. The measurement results show that the near-tip field around the bifurcated crack deviates from the K-field. The stress field around a stationary bifurcated notch is also measured, where the bifurcated notch has the same shape as the bifurcated fast propagating crack. The stress field around the bifurcated notch also deviates from the K-field. The deviation of the stress field of the bifurcated fast propagating crack is qualitatively similar to that of the stationary bifurcated notch. It can thus be said that the deviation of the stress field around a bifurcated fast propagating crack form the K-field is due to the geometrical shape of the bifurcated crack tip.
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Katsuaki FURUKAWA
Article type: Article
Pages
207-208
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The first stage of fatigue is a important problem because its width is very short but its life is 80% of the whole life. But it is well known that the initial crack growth is very fast on the condition of existing compressive stress. The reason is that an crack opening is arose on the behalf of a remained tensile stress. Therefore, in this study the effect of an compressive stress was investigated. As results, it was found that the acceleration of initial crack growth is in the proportion to the power of the compressive stress and striation was found in the initial crack.
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Kazuo ARAKAWA, Toshio MADA, Kiyoshi TAKAHASHI
Article type: Article
Pages
209-210
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Dynamic fracture of PMMA was studied using a Cranz-Schardin high-speed camera. The single-edge-notched specimen was pin-loaded with special fixtures so that it could split and fly away after the fracture. The flying velocity was measured to estimate the elastic energy store in the specimen. In this report, the nonelastic energy was estimated from the visco-plastic deformation to correlate with the external work applied to the specimen.
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Shoji KAMIYA, Hiroki KIMURA, Kiichiro YAMANOBE, Masumi SAKA, Hiroyuki ...
Article type: Article
Pages
211-212
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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A new method is proposed to measure the toughness of thin films prepared on substrates. By partly removing the substrate from the edge of film and substrate, the overhang part of the film projected out of the edge of substrate is prepared as the specimen to measure the film toughness. External mechanical load is applied on this specimen by pushing down both sides of the notch, which is grooved from the free edge of the film to be the starter of crack extension. The crack extension behavior is recorded as the load-crack extension diagram, which is compared to the results of numerical simulation for the the crack extension with the assumed value of toughness. With the correspondence of experiment to simulation, the optimum value of assumed toughness can be determined as the result of measurement. With this method, the toughness of a diamond film deposited on WC-Co was obtained.
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
Pages
213-214
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Adhesion is one of the critical problems for thin film structures, which is quite difficult to evaluate. In this paper, a new method of quantitative evaluation is reported for the adhesive toughness between thin films and sbstrates, which gives an absolute measure of adhesion in term of macroscopic mechanical energy required to extend interface crack of unit area. As an example of application, we evaluated the adhesive toughness between the chemical vapor deposited thin diamond film and the cobalt-cemented tungsten carbide, which was 15 J/m^2.
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Takahiro NAMAZU, Yoshitada ISONO, Takeshi TANAKA
Article type: Article
Pages
215-216
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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This research makes clear the temperature effect on mechanical properties of micro/nano scale Si beams by using Atomic Force Microscope (AFM). The Si and SiO_2 beam were fabricated on a Si diaphragm by means of field-enhanced anodization with AFM and anisotropic etching. The beams were approximately 200-800nm in width and 255nm in thickness. As a result of bending tests, bending strength and Young's modulus of Si beam in the <110> direction decreased with increasing temperature ranging from 295K to 573K.
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Atsushi SUGETA, Yoshihiko UEMATSU, Keitarou TOMITA, Masahiro JONO
Article type: Article
Pages
217-218
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In-situ observation of small fatigue crack growth in α-brass was performed by means of an atomic force microscope (AFM) equipped with a small three-point bending fatigue testing machine. The fatigue crack tip could be located exactly by measuring the variation of crack opening displacement (COD) during one load cycle. It appeared that there was the dependency of the frequent branching and deflection of the main crack on the slip deformation observed on the specimen surface.
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Kenichi SHIMIZU, Tashiyuki TORII
Article type: Article
Pages
219-220
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In recent years, films have been widely used as small-sized and light-weight materials for electronic parts. For reliability of these parts, it is important to know fatigue properties of the film. In this study, the crack initiation behavior from the notch in cold rolled copper films was observed by scanning electron microscope in relation to the crack propagation behavior to the film thickness direction. And an effect of rolling direction on the crack initiation behavior was studied using two types of specimen that rolling direction was parallel and perpendicular to the loading direction.
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Tomohiro KAMATA, Takeshi OGAWA
Article type: Article
Pages
221-222
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Fatigue crack growth tests were carried out for ferrous metals, Al and Ti alloys. Fracture surface morphology was evaluated quantitatively in order to correlate fractography with crack growth rate. Selected locations of fracture surface were observed by SEM. The 3-dimensional configurations of fracture surface were reconstructed by computer software. Normalized surface area and fractal dimension were calculated from the height information of the reconstructed fracture surface.
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Tetsuya NEMOTO, Soichi SASAKI, Hiroshi HACHIYA, Kunihiko TAKEDA
Article type: Article
Pages
223-224
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Fatigue tests in repeated tension-compression have been carried out on the sample of PS (Polystyrene) and PC (Polycarbonate). The crazes that were observed during fatigue test could be classified into two categories. The craze is generated at the direction of an initial crack in the case of PS by continuous mechanical load. And the craze grows up to the crack in the same direction. The plural crazes were also observed in the case of PC by continuous mechanical load. This craze grows up in the direction of angle of stress and 45 degrees. This report advocates the mechanism and critical fatigue point to find high fatigue-resistance materials of polymers.
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Hironori TOHMYOH, Yasuo OCHI, Takashi MATSUMURA
Article type: Article
Pages
225-226
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The surface SH waves technique has been used to evaluate the fatigue cracks at the surface of mild steel specimens. In this study, the diffraction of surface SH waves received by double-probe technique was used. Firstly, the specimens introduced surface slit were inspected. With the results that the amplitude decreased and the propagation time increased with the slit depth. Secondly, the length and the depth of the fatigue cracks, which initiated at a small drill hole by rotating-bending fatigue, were evaluated with the difference between the propagation time of the inspected plate with crack. With the results that the evaluation of the crack growth behavior showed good agreement with measured values.
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Morimasa Murase, Koichirou Kawashima
Article type: Article
Pages
227-228
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The group velocities of multimode's Lamb waves are simultaneously measured by the phase spectrum method. Multimode's Lamb waves in an aluminum plate of 2.0 mm thickness were generated by the Q-switched Nd : YAG laser. The Lamb waves were received at two different distances using a laser interferometer. The analysis using by the phase spectrum method and moving average enables to measure to the dispersion curves of various modes. The measured dispersion curves agree well with the theoretical dispersion curves in velocity range from 2000 to 3000 m/s and in the frequency×thickness range from 2.0 to 18.0 MHz mm. This method may be effective for detection of various defects in thin plates.
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Ryuji Yamamoto, Daisuke Koyama, Koichiro Kawashima
Article type: Article
Pages
229-230
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Stress distribution on U-notched aluminum and steel plates under tensile load has been measured by a electromagnetic acoustic transducer (EMAT) driven by short pulse and special preamplifier. The shear wave EMAT was excited by a square pulser and the signal was received by a high S/N receiver. The time-of-flight was calculated with 6th and 42th back wall echoes. The polarization direction was also determined within one degree by measuring direction-dependent amplitude. The principal stress difference can be measured within 20MPa, compared with FEM analysis.
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Roziq Himawan, Yoshio ARAI, Eiichiro TSUCHIDA
Article type: Article
Pages
231-232
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In this study an ultrasonic technique for the quantitative nondestructive evaluation of small surface fatigue crack is developed. The use of an oblique longitudinal wave with large angle (over the critical angle) of incidence upon the specimen surface is emphasized. Ultrasonic testing was performed with small surface fatigue cracks and artificial defects. A model based on three dimensional elastodynamics was proposed to simulate this ultrasonic technique, and numerical analysis were done for surface crack reflection problem.
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Yutaka WATANABE, Yoshihiro Saito, Yoshiaki KURATA, Hyunsoo KIM
Article type: Article
Pages
233-234
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Supercritical water oxidation (SCWO) holds a great potential to destroy organic waste. One of the major challenges in this process is to control the corrosion and SCC of structural materials by severe corrosive environment. However compared to the study of chemical processes in supercritical environment, there are only a few studies regarding corrosion and SCC. The cracking of an autoclave made of Hastelloy C-276 has been analyzed in this study. The autoclave was used to study the corrosion mechanism of SUS316 in sodium chloride solutions under supercritical and subcritical conditions. The results revealed the importance of the environment inside the cracks for crack growth. The probable mechanism for cracking in this supercritical application has been proposed.
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Yu TANAKA, Shuji HATTORI
Article type: Article
Pages
235-236
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The ratio of air content from 0.75 to 1.5 to that in ordinary ion exchanged water does not affect the cavitation erosion of aluminum which was obtained in aerated or deaerated ion exchange water. The mass loss rate in water/ethanol liquid is proportional to the product of (vapor pressure)^<-0.9> and (the ratio of air content)^<-3.1>. Considering these two findings, it was concluded that there exists the critical ratio 1.6 of air content which begins to decrease the erosion rate. Moreover, it was found that the mass loss rate in various test liquids corresponds well with a summation of square of impact loads.
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Akinobu KAWANO, Noriyuki HISAMORI, Akira NOZUE
Article type: Article
Pages
237-238
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The number of aged person is increasing having a disease for bone, tooth, and innards. So the necessity of these substitute materials must be increasing. Alumina ceramics are used for substitute materials as bonehead of a thighbone joint, because of its high strength and bioinert properties. For many biomaterials a fracture occurs due to both corrosion and fatigue. In this study, effects of similar body fluid (SBF) environment on mechanical properties and microstructure of Al_2O_3 were investigated. Microstructural changes of Al_2O_3 ceramics due to SBF corrosion degradation were also examined by SEM after long time immersion into SBF at 37℃. Degradation of bending strength and fracture toughness (K_C) were evaluated.
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Motoki TAKATA, Takuya YAMAZAKI, Byungjun LEE, Jun KOMOTORI
Article type: Article
Pages
239-240
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Fretting fatigue is known as a cause of failure of implant materials. The aim of this study is to evaluate the fretting fatigue properties of T-i-6Al-4V alloy in air and in a simulated physiological environment. In a relatively high stress amplitude region, there is no difference of fatigue life between two environments. However, fatigue strength at 4.0×(10)^7 cycles in a simulated physiological environment is higher than that of in air. This is because the crack propagation rate in a simulated physiological environment is lower than that of in air due to corrosion products.
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Kazunori MISAWA, Tomonaga OKABE, Masaaki YANAKA, Nobuo TAKEDA, Masao S ...
Article type: Article
Pages
241-242
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The damage process of TiN thin film has been studied and the elastplastic shear-lag approach which consider the plasticity of substrate is proposed to evaluate the damages under the monotonic loading. In order to assert the validity of the present approach, we conducted the elastoplastic FEM analysis based on the strain increamental theory. The present results have good agreements with FEM results. The strength properties of TiN film were obtained with the Monte Carlo simulation using the present approach.
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Tadaaki SAKA, Takashi NAKAMURA, Toru NOGUCHI
Article type: Article
Pages
243-244
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Compressive strength tests of Giant Magnetostrictive Materials fabricated by powder metallurgy were carried out and the effect of aspect ratio of test pieces and elastic modulus of compression plates were examined. Influential factors on compressive strenght were investigated through observation of fracture behavior, SEM fractography and stress analysis of a specimen near its contact surface. As a result, it was clarified that compressive strength decreased as aspect ratio decreases when elastic modulus of compression plate was high whereas it remained constant without being affected by aspect ratio when elastic modulus was low. This result was well explained by very low tensile strength of Giant Magnetostrictive Materials and tensile stress distribution near the contact surface, which was generated by the difference of elastic deformation between compression plate and test piece.
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Kenji Gomi, Yasushi Niitsu, Kensuke Ichinose
Article type: Article
Pages
245-246
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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We have developed equipment to measure optical birefringences in commercial LEC-grown GaAs (100) wafers by using a photoelastic modulator and a polarized laser. A He-Ne infrared laser was utilized as the light source for measurements of strain-induced birefringence in the GaAs wafers. The residual strain and stress components were calculated from the values obtained experimentally. The residual stress profiles have been evaluated to explain the correlation between the residual stress and thermal-stress-induced dislocation. It was found that the optical birefringence equipment developed for this study possessed the needed sensitivity to evaluate residual stress profiles of commercial GaAs (100) wafers. We have discovered the relation between the crystal gliding (translation gliding) and the process-induced stressesat 700℃ on GaAs (100) wafers.
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Yang JU, Masumi SAKA, Hiroyuki ABE
Article type: Article
Pages
247-248
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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A nondestructive inspection system using millimeter-wave was developed for detection of delamination in IC packages. An open-ended coaxial line sensor was used as a source and also a receiver of millimeter-wave signal that was transmitted into and reflected from the packages. The phase of the reflection coefficient was measured for obtaining the information of the delamination. The package was scanned in two perpendicular directions on a plane parallel to the package. A two-dimensional image was created by using the raw data of the millimeter-wave measurement. The millimeter-wave image showed almost same feature as that of scanning acoustic tomography. The delamination was detected significantly without coupling medium. The millimeter-wave inspection system was proved to be a powerful tool for the integrity assessment of IC packages.
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Masakazu TAKAGAKI, Toshiya NAKAMURA
Article type: Article
Pages
249-250
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In the present study, the analysis method of the propagation behavior for the multiply distributed cracks is proposed by means of local approach of fracture (LAF). It is difficult to calculation the propagation of multiply distributed cracks based on fracture mechanics because it takes many calculation time and the cast. The simple analysis method is therefore required. Though LAF is generally applied to isotropic damage parameter, the result of the FE-analysis using isotropic damage parameter because the dynamic effect of actual cracks has anisotropic. So we propose the simple method based on damage mechanics to conduct the finite element analysis method considered the anisotropic dynamic effects of every crack.
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Ichiro SHIMIZU, Takeji ABE
Article type: Article
Pages
251-252
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The surface roughening topography on the free surface of polycrystalline metal has important information for understanding the inhomogeneous deformation behavior during plastic deformation. In the present study, the three-dimensional surface shapes of pure aluminum in the deformation patterns with different strain ratio as well as torsion test are characterized. The filtering operation and the newly developed evaluation technique of anisotropy are adapted to the roughened shape measured by the stylus instrument. The differences in the characteristics of surface topography in various plastic deformation is well characterized, thus the influence of macroscopic deformation pattern on the microscopic inhomogeneity of polycrystalline metal is discussed.
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Kenichi OSHITA, Kenji HATANAKA
Article type: Article
Pages
253-254
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The stress rate-controlled tensile tests were performed for notched specimens of the sintered silicon nitride ceramics with projections at 1300℃. Then the displacements were measured by means of the laser-beam-type displacement measuring system. It was shown from the tests that inelastic deformation was easier to generate at lower stress rate. The constitutive equation was constructed on the basis of tensile stress-strain curves on the smooth specimens presented in the authors' earlier paper, and the inelastic FEM analysis was performed for the smooth and notched specimens, using this equation. These calculations slightly underestimated yield stress of the notched specimen. It, however, was shown that the analytical method proposed in the present study was useful for analyzing the inelastic deformation behavior of notched specimens in Si_3N_4 ceramics at 1300℃.
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Kengo FUKAZAWA, Tomonaga OKABE, Masao SHIMIZU
Article type: Article
Pages
255-256
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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A Monte-Carlo simulation was developed in order to propose a new model for the fracture process of high strength steel in high and extremely high cycles fatigue regions. The analysis results of the proposed model were almost accordance with the experiment result, and it was shown that this model could make the prediction of fatigue life of high strength steel. And it was shown that the fish-eye failure could be appeared even for the low and middle strength steel in an extremely high cycles fatigue region.
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Kazufumi UDA, Ichiro MAEKAWA
Article type: Article
Pages
257-258
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Impact tension was applied to strip specimen with cracks made by PMMA. Cracks was introduced by the razor for specimens before the experiments. Fracture strain εc and εs measured at the crack tip and smooth portion, respectively, of specimen and also the strain concentration factor defined by the ratio K_f=ε_c/ε_s of short specimen was larger than that of long one. However, the factor K_e on the elastic region of long specimen was larger than that of short one. Numerical analysis also showed similar results.
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Yasuhito HORI, Shigetoshi ARAKI, Noriyoshi DOHARA, Kenji MIZUKAWA, Ken ...
Article type: Article
Pages
259-260
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Cylindrical non-fused sharp notch is produced between the Erectro-fusion Polyethylene joint and the outer circumferential edge of the Polyethylene pipe in their fusing process. Elastic-plastic fracture toughness J_<IC> of Polyethylene is required for the joint to be designed safely based on fracture mechanics. In the present study, three points bending tests are conducted for single edge notch specimens over the temperature range from -100℃ to 20℃. The value of J_<IC> of high density Polyethylene is evaluated based on ASTM standard E813-81 and on E813-87. Although determination of J_<IC> according to both the standards make difference in its value by 30% over the temperature range from -100℃ to -60℃, J_<IC> values become almost constant within 3.5 to 5kJ/m^2. At the temperature above about -20℃, the value of J_<IC> increases significantly with increasing temperature. Using of E813-87 may cause the pronounced overestimation of J_<IC> value at 20℃.
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Takashi KUBOKI, Pean Yue Ben JAR, Kiyoshi TAKAHASHI, Tetsuya SHINMURA
Article type: Article
Pages
261-262
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Tensile and Izod impact tests were used to evaluate effect of silicone oil on mechanical properties of high impact polystyrene (HIPS). Two types of HIPS were used for the study. One contains core-shell type particles with average diameter of 0.4 μm (0.4CSL), and the other salami type particles with average diameter of 1.0 μm (1.0SH). Results show that by adding the silicon oil, total fracture energy for 0.4CSL was increased only at the addition of 0.5 wt% under tensile test, but decreased under Izod impact test; while for 1.0SH the addition of silicone oil increased total fracture energy for both tensile and Izod impact tests. The study also included deformation analysis using optical microscopy. In this paper, the relationship between the fracture energy and the size of the whitening zone is discussed.
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Jianqiao CHEN, Shigeo TAKEZONO, Katsumi TAO, Masamichi NAGATA
Article type: Article
Pages
263-264
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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For a quasi-isotropic CFRP laminate, the elastic stress-strain behavior is expected to be the same in any directions. But fracture and/or strength of it may strongly depend on the loading direction. In this paper, tensile tests are carried out for the specimens, cut out in three directions from two kinds of quasi-isotropic CFRP laminates, to investigate the influence of loading direction on the damage pattern and final fracture. A FEM code is used to analyze the stresses, and an attempt to compare the numerical analysis with the experimental observations is made.
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Yuichi TAJIMA, Motomichi ITOU, Yoshizumi NAKASUJI, You Chul KIM
Article type: Article
Pages
265-266
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Joining dissimilar materials, residual stress is necessarily generated. Causing this residual stress, the bonded interface may be separated or fractured. In this paper, residual stress through the thickness generated in Al/Al_2O_3 diffusion bonds was measured. According to the results, residual stress generated in Al substrate of which thermal shrinkage was larger than Al_2O_3 substrate was tensile. Therefore, residual stress in Al_2O_3 substrate was compressive near the interface. Residual stress generated in Al_2O_3 substrate showed the feature like as pure bending moment had been applied.
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Nobuyuki TANAKA, Yasuyuki KATO
Article type: Article
Pages
267-268
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Recently, the laser processing is widely applied in the various fields of the industrial production. Especially, fusing, welding, trimming and so on have already been well known. However, the bending of the thin plate by the laser processing is hardly known. As the first step of this study, the single irradiation that is the most fundamental case is considered in this paper. The limit analysis combined loading of the membrane deformation and bending deformation is carried out by using the radial flow rule as the plastic flow rule. Moreover, the distribution of the deflection under the plastic deformation and spread of a plastic region, which grows in the neighborhood of the irradiation portion, are being examined.
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Yasuhiro SHIMAHASHI, Seiji HAYASE, Hayato FUKUSHIMA, Masakatsu SUGIMOT ...
Article type: Article
Pages
269-270
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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It becomes clear that the predominant cause of the formation of circumferential residual stresses in sunk tubes is the axial unbending of the wall element of the product at the exit of the die. The theoretical distributions of residual stresses through the wall thickness are calculated by the elasto-plastic finite element method and compared with the experimental results of mild steel products. It is also shown that the magnitude of the residual stresses near the inner surface is great enough to satisfy the yield condition of material.
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Tomoaki KASHIMA, Noboru TOMIOKA, Akifumi OKABE
Article type: Article
Pages
271-272
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The joint stiffness of jointed part in automobile body structures is one of key factors domination the basic characteristics of body such as strength, a vibration and a collision. The technique to evaluate the joint stiffness using joint stiffness matrix has been suggested. In general, each element of the joint stiffness matrix can't be determined. If the method capable of determining each element of the joint stiffness matrix quickly and accurately is developed, it must be useful in designing body structure. In this paper, a new method to estimate of the jointed stiffness matrix using hierarchical neural networks is described.
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Yoshiaki AKINIWA, Keisuke TANAKA, Hidehiko KIMURA, Atsushi HAYAKAWA
Article type: Article
Pages
273-274
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Fatigue tests were conducted on SCS-6/Ti-15-3 composite, Initiation and propagation behavior of small fatigue cracks with the debonding between the matrix and rainforcement-fibers were observed on replicas taken during fatigue test using a scanning electron microscope (SEM). Fatigue cracks propagate with debonding in the fiber/matrix interface without fiber breakage under lower applied stress. On the other hand, fiber breakage becomes dominant under higher applied stress. The length of debonding increased with distance between the interface and the crack-tip.
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Masayuki AKITA, Masaki NAKAJIMA, Keiro TOKAJI
Article type: Article
Pages
275-276
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Takeshi TOMINAGA, Yousuke Wakabayashi, Yoshihito KUROSHIMA, Syoji HARA ...
Article type: Article
Pages
277-278
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Ton That Kiem, Shinichi Nishida, Nobusuke Hattori
Article type: Article
Pages
279-280
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Small fatigue-crack growth in annealed 1050 and 7075 aluminum alloys have been investigated by rotating bending test. In 1050 alloy, larger grain size reduces the fatigue strength and a fatigue limit almost equal to the yield strength is obtained in 1050 alloy with grain size of 200μm. This fatigue limit is apparently determined by the critical cyclic stress for the small crack propagating through the grain boundary. Though the same trend was observed in 7075,i.e. fatigue strength tends to reduce with a coarser microstructure; small crack growth in 7075 is strongly influenced by the size and particularly the spacing between insoluble particles rather than its grain boundary.
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Keiro TOKAJI, Yoji GOSHIMA
Article type: Article
Pages
281-282
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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DeHua MIAO, Shinichi NISHIDA, Nobusuke HATTORI
Article type: Article
Pages
283-284
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Fatigue test has been performed to investigate the torsional fatigue properties of pre-strained carbon steel (S45C). Main results summarized in this study are as follows : (1) In the case of plastic pre-strain rate ε_p≦5%, the fatigue limit is 10% lower than the non-pre-strained specimen. Even if the pre-srtain rate increases, the fatigue limit is almost the same one. (2) In the case of ε_p>5%, the fatigue limit increases with increasing pre-strain rate. For the ε_p=8%, the fatigue limit equals to fatigue limit of non-pre-strained specimen. (3) The non-propagatinig cracks are observed in all specimen's sufaces after suffered by 1×(10)^7 cycles under the stress amplitude of fatigue limit. The length of non-propagating crack of pre-strained specimen has no obvious difference with that of non-pre-strained specimen. On the other hand, the higher the pre-strain rate, the more number of non-propagating cracks are observed in the specimen's suface.
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Jin NAGATA, Masashi TAKAGAKI, Byung Jun LEE, Jun KOMOTORI, Kuninori MI ...
Article type: Article
Pages
285-286
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The purpose of this study is to investigate the effect of the hybrid surface modifications on the fatigue properties of titanium alloy (SP-700). Rotational bending fatigue tests were performed on five types of specimens with different surface treatments. The results are summarized as follows : 1) The fatigue strength of the WPC treated specimen was larger than that of the untreated specimen. This is because, WPC process generates the hardened layer with compressive residual stress. 2) There was no difference in fatigue strength between the untreated and the physical vapor deposited specimen. At high stress levels, however, the fatigue lives of the specimen with TiN film were longer than that of the untreated ones. 3) The fatigue strength of the hybrid surface modified specimen was decreased less than that of the WPC treated specimen. This is because, the heat treatments during PVD process reduce the compressive residual stress.
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Shuji Hattori, Mitsuaki Gotoh
Article type: Article
Pages
287-288
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The plastic strain range of stress-strain curve during fatigue process was measured for an annealed and a rolled steel for general structure SS400. The movable dislocation density was estimated from the plastic strain range. It was found that variation in movable dislocation density ρ was expressed as a function of the number of stress cycles n by following equation using a model based on the multiplication and annihilation process of dislocations. [numerical formula] It was concluded that the calculation using this equation corresponds well with the movable dislocation density estimated from the plastic strain range.
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Yukitaka MURAKAMI, Satoru ODAHARA, Masahiro INOUE, Atsuo SUEOKA
Article type: Article
Pages
289-290
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Keisuke TANAKA, Yoshiaki AKINIWA, Makoto SEGAWA, Yoshihisa SAKAIDA
Article type: Article
Pages
291-292
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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To determine the fatigue fracture mechanisms of notched specimens of porous silicon carbide with a porosity of 37% and a mean pore size of 10μm, cyclic fatigue tests were carried out using four-point bendeing loading at room temperature. The crack length was determined from the compliance change under the assumption that the compliance change is caused solely by crack growth. The fatigue life increased with decreasing nominal stress level. The crack propagation rate first decreased with crack extention, and then turned to increase at crack length above about 0.7mm. SEM observations indicated that a fatigue crack grew in the bonding layer between particles.
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Jeongseok OH, Byungjun LEE, Jun KOMOTORI, Masao SHIMIZU, Katsuyuki SHI ...
Article type: Article
Pages
293-294
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Fatigue strength and fracture mechanism of a medium carbon steel (S35C) with gas flame thermally sprayed Co-based alloy coatings were investigated by rotating bending tests. The fatigue characteristics depend on coating thickness, and fatigue strength increases with increase in coating thickness. The result showed that at lower stress levels, the fatigue cracks were initiated inside the substrate of 0.3mm and 0.5mm coated specimens only (Internal failure in the substrate). On the other hand, at higher stress levels the fatigue cracks were initiated at the coating layer, which were originated from the porosity located in coating layer of all coated specimens (Surface failure in the coating layer). But on fracture mode transition was noticed for the case of 1.0mm coated specimen.
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