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Toshio Hayashida, Ryosuke MATSUMOTO, Michihiko NAKAGAKI, Noriyuki MIYA ...
Article type: Article
Session ID: 3331
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A series of molecular dynamics (MD) simulations of severe simple-shear deformations, which are ideally equivalent to SPD applied by typical processing routes of Equal Channel Angular Pressing (ECAP), is performed using three-dimensional models with periodic-boundary condition. We analyze the influence of initial grain size on the microstructural evolution. In the result, it is apparent that defects are introduced into grain efficiently in case of large grain size.
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Hiromoto KITAHARA, Taro MAEKAWA, Nobuhiro TSUJI
Article type: Article
Session ID: 3332
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This study was carried out to clarify the microstructure and mechanical properties of martensite transformed from ultrafine grained (UFG) austenite fabricated by the accumulative roll-bonding (ARB) process in an Fe-29.6wt.%Ni alloy. The sheet ARB processed by 5 cycles (equivalent strain:ε=4.0) showed the ultrafine lamellar austenite grains with the mean lamellar spacing of 230nm. The martensite transformation starting (Ms) temperature decreased with increasing the ARB strain. The nano-martensite transformed from the UFG austenite showed characteristic morphologies and performed very high strength up to 970MPa.
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Yuji NAKASONE, Yoshifumi IWASAKI
Article type: Article
Session ID: 3333
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The present study has investigated crack growth behavior in the nano-crystal powder alloys of GIGAS 20, 30 and 50. Crack propagation tests were made on CT specimens of these alloys at 297K in air under tension-to-tension fatigue loads at three levels of stress ratios, R=0.05 to 0.2. Curved crack propagation was observed in CT specimens of GIGAS 20 and 50, whereas cracks always propagated straight in those of GIGAS 30. Crack closure effects were measured by strain gages mounted near crack tips and on the back surfaces. Crack propagation paths were tracked by advanced CCD camera mounted on a tri-axial X-Y-Z positioning table. The values of the mode I and II stress intensity factors K_I and K_II for curved cracks so observed were calculated by FEM. Crack propagation rates da/dN were plotted against the effective stress intensity factor range ΔK_<eff> and compared for three types of the present nano-crystal alloys tested. The relations between instantaneous crack propagation angle θ and K_II/K_I ratio were also calculated and found to take a sigmoidal curve.
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Kazuki TAKASHIMA, Masaaki OTSU
Article type: Article
Session ID: 3334
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A microscale fracture testing has been applied to investigate the fracture properties of lamellar colonies in a fully lamellar Ti-46Al-5Nb-1W alloy. Micro-sized cantilever specimens with a size≈10x15x50μm^3 were prepared from one lamellar colony by focused ion beam machining. Notches with a width of 0.5μm and a depth of 5μm were also introduced into the micro-sized specimens by focused ion beam machining. Fracture tests were successfully completed using a mechanical testing machine for micro-sized specimens at room temperature. The fracture toughness values were obtained in the range 2-7MPam^<1/2>. Fracture surface observations indicate that these variations are attributable to differences in local lamellar orientations ahead of the notch. These fracture toughness values are also lower than those having been previously reported in conventional samples. This may be due the absence of significant extrinsic toughening mechanisms in these micro-sized specimens. Fracture mechanisms of these alloys are also considered on the micrometer scale.
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Tatsuya MORIKAWA, Kenji HIGASHIDA
Article type: Article
Session ID: 3335
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The effect of a fine lamellar structure due to deformation twin on the yield strength of fcc ferrous alloys has been investigated by using cold-rolled Fe-36mass%Ni alloy and 310S stainless steels. Microstructural evolution during coldrolling of both alloys has been also examined by using transmission electron microscopy. In cold-rolled Fe-36mass%Ni alloy, a kind of layered cell structure was observed, but no deformation twin was found. On the other hand, in a 310S steel, a fine lamellar structure of twin-matrix (T-M) was markedly developed with cold-rolling. The cold-rolled 310S steels exhibited yield strengths about 2 times higher than those of the rolled Fe-Ni alloys in spite that the yield strength of as-annealed 310S is lower than that of as-annealed Fe-Ni alloy. This indicates that the occurrence of fine T-M lamellae during cold-rolling enhances the evolution of fine-grained structure, which causes the marked increase in the yield strength of the rolled specimens.
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Tetuya Ohashi, H.M. Zbib
Article type: Article
Session ID: 3336
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Ryosuke MATSUMOTO, Ryo ISHIKAWA, Michihiko NAKAGAKI, Noriyuki MIYAZAKI
Article type: Article
Session ID: 3337
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this paper, in order to introduce the mechanical property change which is attributed to the dislocation structure, a formulation for a macroscopic body containing microscopic periodic structure with a polycrystalline structure and dislocations is given based on the homogenization approach.
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Masato WAKEDA, Yoji SHIBUTANI, Shigenobu OGATA, Junyoung PARK
Article type: Article
Session ID: 3338
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Amorphous metals have excellent mechanical properties such as high yield stress and high fracture toughness. However, they hardly exhibit the sufficient plastic elongation due to the localized deformation. To overcome such a defect, the localization mechanism must be resolved and the fracture criterion should be settled for future practical designing. In order to investigate the localization mechanism and to discuss the effects of the temperature and strain rate from the atomistic viewpoint, we construct the computational amorphous alloy models using molecular dynamics technique. Under a variety of environmental temperatures and loading rates, we performed the two-dimensional uniaxial tensile simulations. After large elastic elongation, the homogenous strain state immediately localize in shear deformation without any inelastic strain. These localized deformations, so called Shear band, largely depend on the strain rates and temperature.
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Masaomi NISHIMURA, Kisaragi YASHIRO, Yoshihiro TOMITA
Article type: Article
Session ID: 3339
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In the present study, various amorphous Ni-Al binary alloys are made by usual melt-quench simulation with different Al composition, and then subjected to tension by means of molecular dynamics simulation. It is revealed that the peak stress shows the highest value at the composition of Al-25at%. Then we discuss the internal structure and its stability from the view point of the elastic stiffness coefficient, or the "lattice stability".
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Kenji HIGASHIDA, Tatsuya MORIKAWA, Tetsuro KAWADA
Article type: Article
Session ID: 3340
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Behaviors of fracture and deformation behaviors in a Zr-Al-Ni-Cu bulk metallic glass (BMG) was investigated by using three-point bending tests. Apparent fracture toughness obtained by bending tests was about 40MPam^<1/2> which is comparable to the value of ductile crystalline metals. This high toughness of the BMG should be understood by the cracktip plasticity as well as those of crystalline metals. It is well known that plastic deformation occurs very inhomogeniously when BMGs are deformed at mom temperature. Such inhomogenity is manifested by the appearance of surface steps caused by localized shear deformation. In the present study, TEM observations for shear bands were carried out using foil specimens prepared by FIB technique. In addition, the surface steps due to the localized shear bands near a fracture surface have been examined in detail by using SEM and AFM. The variation of the step height indicates the gradient of plastic shear deformation, and it can be understood, in principle, as the introduction of elastic singularities corresponding dislocations in the case of crystalline materials.
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Yuji NAKASONE, Yoshifumi IWASAKI
Article type: Article
Session ID: 3341
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The present study has investigated fatigue fracture behavior and deformation-induced crystallization in a Zr-based bulk amorphous alloy. Fatigue crack growth tests were performed on center-cracked plate specimens of 55at%Zr-10at%Al-5at%Cu-30at%Ni at room temperature in air. Tension to tension fatigue loads were applied at stress ratios of R=0.05 to 0.3 at a loading frequency of 5Hz. The plastic replication technique was used for observing crack growth behavior. Crack branching, crack deflection and non-propagating branches frequently occurred at specimen surfaces of the amorphous alloy. Thus, the crack growth rate vs. stress intensity factor range diagrams in which projected crack length was used fluctuated widely. This anomalous growth behavior can be attributed to the fact that internal crack surfaces were very rough. Roughness-induced crack closure was observed at stress ratios lower than 0.3. Scanning electron microscopy revealed striation-like patterns in some portions of the rough crack surfaces. Spot X-ray diffraction analysis with a focal diameter of 30 micrometer of crack surfaces were also made and detected localized crystallization in the form of Zr_2Cu. The localized crystallization may have been brought about by severe deformation in the vicinity of crack tips. The striation-like patterns were produced in some portions of crack surfaces so crystallized. Sparks were observed emitted from growing fatigue cracks just before fracture by the high-speed camera.
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Masayuki ARAI
Article type: Article
Session ID: 3401
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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It is very important to comprehend growth behavior of an interfacial oxidation formed between ceramic coating and bond coating layers in thermal barrier coating systems and predict its oxidation grown thickness in high-temperature components of gas turbine, because of preventing these coated components from TBC delamination damage. A lot of oxidation growth curves against exposure time had been already taken, but its data were limited to exposure time up to 1000hours. In this report, we try to take more long period exposure data and grasp about the associated growth behavior.
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Masayuki ARAI, Eiji WADA, Kikuo KISHIMOTO, Naoyuki OHNO
Article type: Article
Session ID: 3402
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Thermal Barrier Coating (TBC) is fabricated by thermal spray technology. By plasma spraying coating particles are melted in high temperature plasma flow and impinged and deposited continuously to a substrate surface. Since a coating layer is formed in this way it seems that the structure and the mechanical properties of TBC are influenced by spray condition. In this study, we varied the substrate temperature and the particle velocity of the coating material in plasma flow about spray condition in plasma spraying and measured coefficient of thermal expansion, elastic modulus, crack length, Vickers hardness, porosity and bending strength of the ceramic layer.
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S. YAMAGISHI, Takeshi OZAKI, Masakazu OKAZAKI
Article type: Article
Session ID: 3403
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Yasuhiro YAMAZAKI, Taisuke ENDO, Hirotaka FUKANUMA, Naoyuki OHNO
Article type: Article
Session ID: 3404
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The thermal cycle tests of the air plasma sprayed thermal barrier coatings were carried out by means of the electric furnace or the high frequency induction heating system. In this study, the in-situ damage behavior was measured by using the acoustic emission system. The experimental results indicated that the thermal cycle damage occurred in cooling stage mainly. The effects of the heating method and the thermal cycle wave on the damage behavior were discussed.
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Daisuke KANEKO, Kazunari FUJIYAMA, Takashi SAITO, Yoshishige MIZUNO, M ...
Article type: Article
Session ID: 3405
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Diffusion and stress simulation analyses were conducted for the oxide layer causing TBC spallation, often observed in gas turbine hot gas path components. Diffusion analysis was based on two processes, that is, the formation of Al_2O_3 layer with internal Al, and formation of composite oxide layer inside of Al_2O_3 layer through diffusion of oxygen. Using the simulated oxide layer shape, elastic analyses were conducted to estimate thermal stress under cyclic thermal conditions and internal stress due to oxide layer expansion. These simulation results showed reasonable shapes and stress distribution of oxide layer and coating system proving that those methodologies were useful for predicting the spalling event for TBC systems.
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Masatoshi TANNO, Kazuhiro OGAWA, Tetsuo SHOJI
Article type: Article
Session ID: 3406
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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To establish the fundamentals of the non-destructive evaluation by using impedance spectroscopy technique, the impedance of a degraded TBC and a stand-alone YSZ were measured using platinum electrodes at temperatures between 300℃ and 1000℃. The impedance spectra of the TBC show the response of the electrode reaction, the thermally grown oxide (TGO) and the YSZ grain in order of the frequency. The impedance of the TGO depends on the asymmetry of electrode and the substrate size. On the other hand, the impedance of the YSZ grain is independent of the asymmetry of electrode and the substrate size. Above 800℃, the contribution of the YSZ grain is negligible, because of very small impedance. The impedance of the electrode reaction is governed by the electrode reaction area and voltage drop caused by the TGO resistance. If the correlation between the TGO impedance and the substrate size was clarified, the TGO thickness could be evaluated quantitatively. The delamination of TBC at the YSZ/TGO interface can be detected by monitoring the impedance of the electrode reaction. Moreover, the degradation of the YSZ top coating can be evaluated by measuring the impedance of the YSZ grain at temperatures under 800℃.
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Satoru TAKAHASHI, Masayuki YOSHIBA, Yoshio HARADA
Article type: Article
Session ID: 3407
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In order to clarify the failure behavior of plasma sprayed thermal barrier coating (TBC) systems under the complicated modes of thermal-mechanical-chemical loadings, the stress rupture property evaluation and failure analysis were conducted in air and high-temperature corrosive environments for two kinds of ZrO_2-Y_2O_3 TBC systems ; one is an advanced type with the segmented top-coat and another is a conventional one. Static creep loading was found to cause the typical creep failure for both TBC systems even in the aggressive environment with almost similar manner to in air. On the contrary, it was revealed that dynamic fatigue loading tends to bring about a significant rupture life reduction both in air and in corrosive environment, since the penetration crack pre-existing in the top-coat is capable to provide a nucleation site for the fatigue crack. For the TBC system with the segmented top-coat, however, the even distribution of a number of fatigue cracks is effective to suppress substantially a rapid crack propagation, so as to result in the prolonged failure life as compared to the conventional TBC system.
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Eiji Nishioka, Atsushi Watanabe, Makoto Nagase, Masao Furukawa
Article type: Article
Session ID: 3408
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Erosion by water drops is occurred on a low-pressure blade in the steam turbine. An electro-spark deposition (ESD) can fabricate a ceramics coating, high hardness, on a substrate which is remained at low temperature in the coating period. The applicability of ESD was examined for the steam turbine with the erosion. Cracks on the surface of the coating can be controlled by preheating of a substrate. The erosion rate of the ESD coating is 1/4 or less than one of the substrate. A bending strength of the ESD coating is equal to the substrate without the coating and the ESD coating is not detached form the substrate at the fracture point. These results show that the ESD coating has properties of the erosion resistance and the mechanical adhesion to the substrate.
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Yoshinori ISOMOTO, Toki YOSHIDA, Yoshikazu YAMADA, Toyoaki YASUI
Article type: Article
Session ID: 3409
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Turbine blades operated at high temperature environments recently tend to suffer severe damage due to oxidation and erosion caused by iron oxide particles. New development and evaluation of high performance coating materials is indispensable in order to achieve long term operation and high quality maintenance. A coating material which consisted of substrate material of SUS410J1 steel and double layers of plasma nitride and chromium nitride was prepared. The tests of solid particles erosion, single particle impact and fatigue were performed under respective environmental conditions at room temperature and 723K. It was concluded that the coating material tested in this study showed high resistance to erosion and fatigue at a temperature of 723K as same as a virtual one on the turbines.
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Kenjiro KOMAI, Naoki YASUMARU, Kenzo MIYAZAKI, Junsuke KIUCHI
Article type: Article
Session ID: 3410
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We report tribological properties of diamond-like carbon (DLC) film of which surface has been nanostructured with femtosecond (fs) laser pulses. For this study, the fs-laser processing technology has been developed to produce a uniformly nanostuctured DLC surface over a wide area of 15×15mm^2. The results have demonstrated that the DLC surface has an excellent frictional performance by coating a MoS_2 layer on the nanostructured surface, where the friction coefficient of DLC surface was observed to decrease down to 0.07 from 0.18 for the steel ball and to 0.02-0.04 from 0.08 for the WC-Co ball used in the friction test machine. Furthermore, we have developed the method for the radical deterioration of the tribological property by means of the net-shaped cross scanning of the fs-laser pulses.
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Yasutaka ANDO, Shogo TOBE, Hirokazu TAHARA
Article type: Article
Session ID: 3411
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In our previous study, it was proved that diamonds could be deposited on thermal spray coated substrate without peeling of and break down of the thermal spray coating even in case of combustion flame CVD by cooling substrate surface during deposition. In this study, to develop easy diamond/metal binary coating deposition process, diamond deposition on the as-deposit thermal sprayed Mo coating was carried out. Consequently, even in case of as-deposit Mo coating, diamonds could be deposited and rigid diamond/Mo complex coating could be deposited by additional Mo thermal spraying after diamond deposition. Besides, the complex coating had higher wear resistance in comparison with the normal Mo thermal spray coating.
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Makoto WATANABE, Seiji KURODA, Kensuke YOKOYAMA, Yoshihiko GOTOH
Article type: Article
Session ID: 3412
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Interfacial fracture toughness and through-thickness residual stress distribution of HVOF sprayed SUS316L stainless steel coatings on carbon steel substrates were investigated in order to examine the reliability of a newly developed evaluation technique and to study the effects of residual stress fields onto the strain energy release rate at the interface cracks. The measurements of interfacial fracture toughness were carried out by modifying the conventional tensile adhesion test method by inserting a carbon layer at the interface to form an interfacial pre-crack. Residual stress distribution was evaluated by measuring the relaxed strain at the substrate surface for reduction of the coating thickness. The modified technique showed good reproducibility for the samples deposited under various spray conditions. The correlations between the toughness and residual stress fields will be discussed.
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Makoto IMURA, Tetsusei KURASHIKI, Hiroaki NAKAI, Masaru ZAKO
Article type: Article
Session ID: 3413
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Woven fabrics have been applied widely to many structures. There are many requirements that need to analyze at the micro level. In order to investigate the behavior of the fibers of woven structures at the micro level, a new computational method that the mechanical behavior of composite materials with a large-scale difference can simulate have to develop. Therefore, we have proposed FEM with mesh superposition in 3 scales, and we have defined the new numerical technology as 'M-cube (Macro-Meso-Micro) method. In addition, the method has been expanded with elastic-plastic and damage mechanics to investigate the propagations of transverse crack in fiber bundles as an initial damage mode. The numerical results will give very important information to evaluate the safety of composite structures.
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Tetsusei KURASHIKI, Masaru ZAKO, Hiroaki NAKAI, Satoru HIROSAWA, Makot ...
Article type: Article
Session ID: 3414
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Woven fabric composites with spread tow may induce better resin impregnation and mechanical properties than the conventional woven architectures. However, the mechanism of damage development in the woven fabric composites with spread tow has not been investigated completely. To investigate the effect of spread tow on the damage development, we have developed the numerical simulation procedure of the mechanical behavior based on damage mechanics. The macroscopic behaviors and microscopic damage states of woven composites with spread yarn are analyzed with multi-scale analysis of M^3 method. It is difficult to detect the strain level of the initial failure by the experiments, however, the strain of initial damage can be evaluated conveniently with the simulation. It is revealed that woven FRP with spread yam has good mechanical properties as compared with the conventional architectures.
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Satoru HIROSAWA, Tetsusei KURASHIKI, Hiroaki NAKAI, Masaru ZAKO, Stepa ...
Article type: Article
Session ID: 3415
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Mechanical properties of textile composites are depended on many variables such as the number of fibers of a bundle, the volume fraction, pitch, kind of material etc. In order to evaluate the properties, a support system for finite element modeling and analysis is needed. We have developed the three programs: Wise Tex, Mesh Tex and SACOM. In this paper, have been described the procedure of design and evaluation of woven fabric composites by the developed computer programs. By the developed programs, the effect of the textile on the local stress or strain distribution, deformation, damaged mode, etc. are investigated easily.
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Yasutomo UETSUJI, Mitsuteru Horio, Eiji NAKAMACHI
Article type: Article
Session ID: 3416
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In order to improve piezoelectric response of polycrystals in a macro scale, micro distribution of crystal orientations was optimized by using multiscale finite element method based crystallographic homogenization theory. As a result, two noteworthy optimum solutions were obtained for micro structure. One is a polycrystalline structure laminated with three specified grains for macro piezoelectric strain constant d_<333>, the other is a polycrystalline structure consisting of two regularly-neighboring grains with specified orientations for d_<311>. As the maximum micro strain occurs by electric and mechanical effects, the optimized micro structures exhibit the highest macro piezoelectricity that is beyond single crystal. Their micro structures are available for piezoelectric ceramics such as BaTiO_3 and Pb (Zr, Ti)O_3, that have the maximum piezoelectric strain constant under off-axis electric field.
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Hiroaki NAKAI, Tetsusei KURASHIKI, Hiromasa TOMIOKA, Masaru ZAKO
Article type: Article
Session ID: 3417
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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To predict the mechanical properties of composite materials by using computer is complicated, because it is difficult to model directly by ordinary FEM. A calculation method by using the mesh superposition method and periodic boundary condition has been proposed in order to obtain the equivalent mechanical properties of composite materials easily. The numerical results by proposed method have shown good agreement with ones by the traditional procedure. The proposed method is efficient for the materials with complicated structure like woven fabric composites etc.
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Takeshi KAWAMURA, Hiroaki NAKAI, Tetsusei KURASHIKI, Masaru ZAKO, Nobu ...
Article type: Article
Session ID: 3418
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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An order-made femoral prosthesis stem made from FRP, of which mechanical properties could be designed, is proposed as an alternative to traditional metal stem which is too stiff compared with human femur. The strength of the stem must be assured. The purpose of this study is to develop an evaluation method of strength for order-made FRP stem by using FEM. FRP stem has been manufactured and mechanical tests have been proceed. FE analyses based on damage mechanics has been carried out. As the results of tests and analyses have a good agreement, it can be demonstrated that the evaluation method by FEM is reasonable.
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Hiroshi Yamashita, Hiroshi Minami, Kiyoshi Tanaka
Article type: Article
Session ID: 3419
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper deals with fracture behavior on Short-beam-bend test of FRP. Mode II interlaminar fracture toughness and interlaminar shear strength are found to have no correlation, despite their in-plane shear stress. It included the examination of fracture behavior and dominant factors of Short-beam-bend test to find out the reason. On the fracture surface of interlaminar shear strength test, hackles and boundary separations and Mode I fracture have been found, whereas only the hackle has been found on the fracture surface of Mode II fracture toughness test. It seemed that Short-beam-bend test is not pure Interlaminar shear faracture test by complicate fractures.
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Hiroshi Minami, Hiroshi Yamashita, Kiyoshi Tanaka
Article type: Article
Session ID: 3420
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper describes about interlaminar fracture toughness of FRP. Mode II interlaminar fracture toughness by 4ENF test is compared with interlaminar shear strength by DNT test and Mode II interlaminar fracture toughness by Notched Short Beam test. In addition, fracture surface of DNT specimen and Notched Short Beam specimen is observed by the scanning electron microscope (SEM). It seems that there is no relationship between Mode II interlaminar fracture toughness by 4ENF and interlaminar shear strength by DNT. But there is a good relation between 4ENF test and Notched Short Beam test.
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Masayoshi YOKOYAMA, Shigetoshi ARAKI
Article type: Article
Session ID: 3421
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Macroscopic coefficients of thermal expansion of a composite material may depend upon both the geometry and the orientation of reinforcements containing in the material in addition to their elastic moduli and coefficients of thermal expansion. In the present study, general expression for macroscopic coefficients of thermal expansion of a composite material, in which many kinds of reinforcements with different aspect ratios and orientations are contained, are derived by using the equivalent inclusion method combined with the Mori-Tanaka theorem. In the analysis, the expression of the equivalent eigenstrain for each reinforcement is derived with respect to the local coordinate system based on its semi-axes and then it is transformed to the global coordinate system. Moreover, numerical calculation is performed to a flake-reinforced composite with a type of orientation distribution of the reinforcements. As a result, we found that a shear component of the macroscopic coefficients of thermal expansion of the composite is non-zero in value.
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Kazuaki SANADA, Yoshihiro TAKADA, Yasuhide SHINDO
Article type: Article
Session ID: 3422
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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To determine the effective elastic properties of a polymer reinforced with aligned carbon nanocoils (CNCs), the finite element analysis were performed using a three-dimensional unit cell model. The coil morphology of CNCs was examined using a scanning electron microscope. The effects of coil diameter, tube diameter, coil pitch and number of coil turns on the effective elastic properties are discussed. The geometrical parameters of CNCs have a slight effect on the effective elastic properties of the material. The effective elastic properties of a polymer reinforced with randomly oriented CNCs were also predicted by the results for unit cell model. The results demonstrate that improvements in the mechanical behavior of polymers are attained through the addition of CNCs as a reinforcing phase.
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Kazunori KANZAWA, Kensuke ICHINOSE, Kenji GOMI
Article type: Article
Session ID: 3423
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In order to obtain data from the viewpoint of non-destructive inspection about a fatigue damage, we applied a low cyclic load in a strain-controled mode with carbon steel plate specimens and observed the surface change. we also applied a monotonic tensile load in the strain-controled mode, and compared it with a low cyclic load. The results obtained are as follows. Stress-Strain Diagram and Cyclic stress-Strain Diagram were accorded in elastic region, and was different after the yielding point. In addition, we were able to confirm that two tests were different in a pattern of Luders band which appeared on the specimen surface in correspondence with yielding stress. Furthermore, we analyzed stress with FEM and compared it with a pattern of Luders band.
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Shin-ichi NISHIDA, Nobusuke HATTORI, Keisuke NAGAKI
Article type: Article
Session ID: 3424
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The adequately fastened screw thread usually shows remarkable high fatigue strength. However, if loosening arise in the screw in the screw thread, all of the external force are directly to the bolt it self and the bolt will be broken catastrophically. The super lock bolt had been developed against such kind of loosening. The object of this study is to investigate the fatigue strength of the above super lock bolt under the different kind of fastening conditions and processing method. In all the test pieces, fatigue strength is improving rather than the common steel bolt.
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Shinichi NISHIDA, Nobusuke HATTORI, Atsushi BABA
Article type: Article
Session ID: 3425
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper describes fatigue properties of plastic deformed stainless steel. Stainless steel has good properties whish are excellent corrosion resistance, tensile strength in high temperature etc. therefore, it has been used for industrial and structural material because of property of maintenance free. Fatigue properties are considered to be one of the most important. There are few reports about which kinds of subjects. Especially, this paper describes fatigue properties of plastic deformed stainless steel which rise remarkably its fatigue limit.
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Shin-ichi NISHIDA, Nobusuke HATTORI, Shougo JINNOUCHI, Tetsuo Tanaka, ...
Article type: Article
Session ID: 3426
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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There actually exist various kinds of fatigue cracks in large scale components. It will be practical important to be able to retard or to stop the fatigue crack propagation. The authors had tried to improve the fatigue life of the cracked specimens by making various kinds of stop-holes at the crack tips and clarified that the stop-holes are very effective for the life extension.
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Shin-ichi NISHIDA, Nobusuke HATTORI, Toshihiko YOSHIDA
Article type: Article
Session ID: 3427
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Investigation is not advancing about the fatigue characteristics of the bolt. Fatigue tests have been performed to evaluate the fatigue strength of high-strength bolt. The specimens prepared what heat-treating after roll-screw-threaded, and which was roll-screw-threaded after heat-treating. The fatigue limit of the specimens of component rolling after heat-treating improved. The main causes are considered to be work hardening and structure miniaturization, fiber flow, and compressive residual stress.
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Tomohiro UENO, Koji TAKAHASHI, Kotoji ANDO, Akitaka HIDAKA, Masakazu H ...
Article type: Article
Session ID: 3428
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Yasuyuki KATO, Takuya MORITA
Article type: Article
Session ID: 3429
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Since the Natural Strain is obtained by integrating an infinitesimal strain increment on an identical line element, this theory has merits that the rigid body rotation can be removed from the rotating angle of a line element and the additive law of strain on an identical line element can be satisfied. Taking the Natural Strain theory into consideration, we investigate the relation between directions of principal axis of stress and strain from experiments in the elastic region by using the specimens, which have already received large multi-axial pre-deformation. In this report, two kinds of different deformation paths, i.e. the simple shear after simple tension and the simple tension after simple shear, are treated as pre-deformation. And, we confirm weather the different deformation history influences on anisotropy of the elastic modulus G.
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Nao-Aki NODA, Ker-Kong Chen, Kiyoshi TAJIMA, Hiromi IMOTO, Takuya TSUT ...
Article type: Article
Session ID: 3430
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Wedge-shaped defects are frequently observed on the cervical region of the human tooth. Previously, most studies explained that improper toothbrushing causes such defects. However, recent clinical obsarvation suggested that the repeated stress due to occlusal force may induce the formation of these wedge-shaped defects. In this study, a two-dimensional human tooth model after a wedgeshaped defect is restored with the composite resin is analyzed by using the finite element method. To obtain the intensity of the singular stress field accurately, a method of analysis is discussed for calculating generalized stress intensity factors, which control the singular stress around the tip of the defect. Then, the relationships between the stress intensity and occlusion are discussed.
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Seiichi OHTAKI, Michitarou OBARA
Article type: Article
Session ID: 3431
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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In this paper, the finite element formulation of the methodology for the calculation of the large deflection of toroidal shells using a mathematical programming technique is presented. Geometrical nonlinearity is taken account of the relation between strain and displacement. The forth-order total potential energy expressed in terms of displacement components is minimized by Davidon-Fletcher-Powell method, and unknown displacements of the nodal points can be obtained. Numerical examples are shown for the pipe bends subjected to in-plane bending to show the effects of the increase of the the stress intensification factor on the geometrical nonlinearity.
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Tukasa SHINOHARA, Takuya KAWABATA, Shozo NAKAMURA
Article type: Article
Session ID: 3432
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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An electronic device is composed of IC chip, substrate, solder ball, QFP package and filling resin. When the electronic device is heated, large thermal stress and warp deformation will be generated in electronic device during the solder joint process and temperature cycling test. In this report, the thermal stress generated in solder joint parts of the electronic device was clarified by Finite Element Analysis. And dangerous parts of fracture in the solder joints were forecasted from the value of the thermal stress caused in each solder joint parts. The result of the calculated values was good agreement with the experimental result.
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Takuya KAWABATA, Tukasa SHINOHARA, Shozo NAKAMURA
Article type: Article
Session ID: 3433
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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An electronic device is composed of IC chip, substrate, solder ball, semiconductor package and filling resin. The thermal stress in solder joint parts of the electronic device and warp deformation of the substrate will be generated, when thermal load is applied to it during the manufacturing process and the environment. Especially, when a large thermal stress was generated in the solder joint parts, the solder will be fractured. In this report, thermal expansion coefficient and transition temperature of filling resin were variously changed, and thermal stress in the solder joint parts was analyzed by FEM. As a result, the optimum design manual of the filling resin was obtained.
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Kazuyuki HIROTA, Mitsuo NOTOMI, Pak-kon Choi
Article type: Article
Session ID: 3434
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The ultrasonic attenuation of Ni-Ti shape memory alloys is investigated over kilohertz range. There are three kinds of wire shape specimens, which are heat-treated by 400, 450 and 500℃. The martensitic transformation temperatures are obtained using by dynamic mechanical analysis and differential scanning calorimeter. Ultrasonic wave is carried to the specimen and the vibration is translated to the voltage by the sensor. The voltage, which is induced by the wave, is measured both input side and output side on the specimen and then the attenuation is obtained by differentiated voltages. The attenuations are measured during heating and cooling. It was found that some of attenuations vary at the temperature on which the specimens transform from martensite to austenite or vice versa.
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Hideaki TANAKA, Mitsuo NOTOMI
Article type: Article
Session ID: 3435
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The B19' martensite phase in Ni-44.55wt%Ti shape memory alloys were investigated by means of the X-ray diffraction. Several X-ray patterns were measured at lower and higher temperature of martensitic transformation and a X-ray pattern simulation by RIETAN-2000 added to determine the crystal structure. At higher temperature than that of martensitic transformation all of crystal consisted in B2 structure. However, the crystal structures at lower temperature of -10℃ consisted in not only B19' but also B2. The ratio of both structures might be 1:1 at martensite phase.
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Masatoshi NOMURA, Mitsuo NOTOMI
Article type: Article
Session ID: 3436
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This study examined the shape recovery rates of single atom system metals, such as Ni, Cu, Al, Ag, Mg, Co, Fe, Ti and Zr. First, all metals are treated by heat for the memory of straight shape, and bended to a semi circular shape along the attachment at room temperature. After releasing the initial strain is measured and reheated. The shape recovery ratio is determined by the initial and final strain that is obtained after reheating. In the metals that don't have martensitic transformation, Ni, Cu, Al, Ag did not exhibit shape recovery, while Mg exhibited a slight shape recovery and the recovery ratio was about 3%. In the metals that exhibit martensitic transformation, Co and Ti exhibited shape recovery about 40% and 30%, respectively, and Fe didn't shape recovery. While, the deformation of Zr is very special. The Zr that was heat-treated at lower temperature than the transition exhibited the shape recovery and however, the Zr that was treated at higher temperature exhibited more deforming to the reverse direction to the recovery.
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Hiromasa SENBA, Nagatoshi OKABE, Xia ZHU, Keisuke OKITA, Kiyoshi YAMAU ...
Article type: Article
Session ID: 3437
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This paper deals with seismic characteristics of the single-stage bellows of Ti-Ni shape memory alloys, which are proposed as a new type of seismic elements. The single-stage bellows of different shapes are formed with the rubber bulge method and prepared for the dynamic tests. Tension-compression cyclic tests are carried out with increasing the displacement amplitude for them. Their effective stiffness and equivalent damping are standardized and estimated from the cyclic loops. Then the effects of bellows shape on dynamic properties are clarified. It is showed that nominal secant stiffness (effective stiffness) is strongly associated with shape factor H/Lw (H: bulge height, L_w: bulge width) of a single-stage bellows and that it can be expressed as a function of the coefficient of stiffness concerning the bulge shape and the material's stress strain characteristic.
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Shijie ZHU, Masanori OKAZAKI, Arimitsu USUKI, Makoto KATOH
Article type: Article
Session ID: 3438
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Takashi ONOZATO, Hideaki ITO, Tsutomu EZUMI
Article type: Article
Session ID: 3439
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The impact phenomena have probrems of the stress wave propagation and the material property. Therefore, the impact phenomena are complex. The flow of power on the interface in the composite materials and the laminated materials is complicated and there are a lot of related factors of the complexity of the contact condition. From this cause, stress analysis and the strength evaluation are difficult. In this study, we made the laminated materials bonding different polymeric materials, and analyzed the dynamic fracture behavior of the interfacial crack with a high-speed video camera. The displacement of the interfacial precrack tip proximity was measured by using the digital image correlation method for the analysis.
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