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Article type: Cover
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Cover1-
Published: September 20, 2002
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Article type: Appendix
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App1-
Published: September 20, 2002
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Article type: Index
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Toc1-
Published: September 20, 2002
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Yasuyo MAGARA, Muneyuki YOSHIDA, Yasuhide SHINDO, Fumio NARITA, Katsum ...
Article type: Article
Pages
1-2
Published: September 20, 2002
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The fracture behavior of a piezoelectric ceramic under applied electric fields has been discussed through experimental and theoretical characterizations. The modified small punch (MSP) tests were performed on a commercial PZT ceramic. The fracture initiation loads under different electric fields are obtained from the experiment. A nonlinear finite element analysis was also employed to calculate the deflection and MSP energy. An expression is presented for determining the fracture properties due to electrical effects by expreimental and theoretical means.
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Muneyuki YOSHIDA, Keisuke HAYASHI, Fumio NARITA, Yasuhide SHINDO
Article type: Article
Pages
3-4
Published: September 20, 2002
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The static electromechanical response of piezoelectric laminated actuators in examined both theoretically and experimentally. A laminated beam theory solution in developed for the cantilever PZT/metal/PZT actuator, and the effects of electrical load on the field-induced displacements of the actuators are analyzed. The mathematical procedure of the present analysis is simple and clear, and the resulting solutions for the displacement of the cantilever laminated beam actuator are highly accurate. A nonlinear three-dimensional finite element model incorporating the polarization switching mechanism with the displacement calculation is also developed. Bending tests are used to validate the theoretical predictions, using laminated actuators made with P-7B piezoceramics and Fe-48Ni host material. Theoretical predictions of the electromechanical displacement and polarizatin switching properties are in excellent agreement with measured values.
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Shigeru KUROSAKI, Kenichi YAMAGUCHI
Article type: Article
Pages
5-6
Published: September 20, 2002
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The piezoelectric polymer film (PVDF) of the marketing was cut down in the rectangle, and the strain gage model was produced experimentally. it is called the piezoelectric polymer thin film strain gage. The strain analysis style was deduced from the piezoelectric polymer thin film strain gage model of the rectangle. Using produced piezoelectric polymer thin film strain gage, the experiment was carried out actually. The test pieces used band plate with (1) center circular hole and (2) edge circular hole notch board. Both strain distributions were measured and the comparison examination was carried out by the combined use of strain gage.
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Mamoru MIZUNO
Article type: Article
Pages
7-8
Published: September 20, 2002
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Damage in piezoelectric ceramics under mechanical and electrical cyclic loading is represented by a damage variable based on the continuum damage mechanics, and an evolution equation of the damage variable is formulated by taking into account the effect of applied electric field on a fatigue life. In addition, the damage variable is incorporated into a constitutive equation of piezoelectric ceramics by using the modified cubes model; i.e. material constants of the constitutive equation are expressed as a material function of the damage variable. Then, the damage evolution equation and the constitutive equation are applied to a prediction of a fatigue life. Results of the prediction are compared with experimental results, and the validity of formulating the damage evolution equation and the constitutive equation is disussed.
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Byeung Gun NAM, Katsuhiko WATANABE
Article type: Article
Pages
9-10
Published: September 20, 2002
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Crack Energy Density (CED) is known as the well-established fracture parameter that is defined without any restriction on constitutive equations for the ordinary materials and is expected also to describe the fracture behavior of piezoelectric material. In this paper, CED for piezoelectric material is defined from path-independent integral based on energy conservation law. Relationships between CED and other fracture parameters for piezoelectric material are obtained and possibility as fracture parameter of CED for piezoelectric material is examined.
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Hideo NAKAJIMA, Makoto SUGIMOTO, Kazuya HAMADA, Katsutoshi TAKANO, Syu ...
Article type: Article
Pages
11-12
Published: September 20, 2002
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The Engineering Design Activity (EDA) for the International Thermonuclear Experimental Reactor (ITER) was performed from 1992 under the collaboration of Japan, EU, Russia and the US. In the EDA, the Japan Atomic Energy Research Institute (JAERI) developed and tested the CS Model Coil under the international collaboration in order to develop fabrication technology of large superconducting coils and to demonstrate various properties. The CS Model Coil consists of the Outer Module and the Inner Module, which were pre-compressed by about 86 MN at room temperature with pre-compression structures composed of supporting beam and tension rod. Strain gages were attached to the tension rod to investigate the change of pre-compression force during cool-down, energizing, and warm-up. This paper describes the mechanical behavior of the CS Model Coil during cool-down and warm-up based on the measurement result of the tension rod strain.
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Hitoshi TAMURA, Toshiyuki MITO, Yutaka YAMADA
Article type: Article
Pages
13-14
Published: September 20, 2002
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High-Tc superconductor (HTS) has been expected as a current lead between a low Tc superconductor and a power supply for a large-scale superconducting magnet system because of its advantages of a low heat load to a cryogenic system and a high transfer current density. Bi2212 bulk superconductor is a candidate material for this kind of current lead. To design a current lead using HTS, we investigated a thermal contraction, Young's modulus, and compressive strength of a Bi2212 bulk which was prepared by a diffusion process. A method of reinforcement of the bulk using a glass-epoxy was also considered and confirmed its effectiveness.
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Makoto YOSHIDA, Takayuki SUDO, Satoshi TAKADA, Masaki SATOH, Masataka ...
Article type: Article
Pages
15-16
Published: September 20, 2002
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The requirement to minimize weight of a reusable rocket is so severe that the weight savings achievable by developing lightweight components in the secondary structures are significant. The purpose of this study was to develop lightweight components using composite materials such as CFRP (Carbon Fiber Reinforced Plastic) for cryogenic propellant feed lines, valves and tanks. We fabricated CFRP domed elements with a radius of 121 mm and evaluated their cryogenic properties including helium permeation dependency on temperature. The helium permeation rate increased drastically with a decrease of temperature, but no evidence of damage was observed after the temperature recovered from the cryogenic condition.
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Koichi KASHIWAZAKI, Shotaro TANAKA, Toru ITO, Tomoaki TAKAO, Atsuhiko ...
Article type: Article
Pages
17-18
Published: September 20, 2002
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We experimentally studied frictional coefficients on surfaces of Dyneema^[○!R] fiber reinforced plastics that were paid attention as new structural materials of superconduction coils. The frictional coefficients on a surface cut by a diamond cutter were measured; the Dyneema fibers were exposed on the surface. We also measured the coefficients on a grind surface of the plastic on which the Dyneema fibers were not exposed. We measured the coefficients on the two kinds of the surfaces at three temperatures (room, liquid nitrogen, liquid helium), and discussed the expermental data.
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Atsuhiko YAMANAKA, Satoshi NAGO, Kenji HOSOYAMA, Toshihiro KASHIMA, To ...
Article type: Article
Pages
19-20
Published: September 20, 2002
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High field superconducting solenoid magnets sometimes quench by wire motion induced by electro-magnetic force. High strength polyethylene fiber reinforced plastic (DFRP) has negative thermal expansion coefficient and low frictional coefficient. DFRP pipes made by filament winding method could be constructed so as to expand in the circumferential direction when cooled to low temperature with an appropriate selection of winding angle and shape of the pipes. In the case of a superconducting coil wound on a DFRP bobbin, it is expected that wire motions in high field are decreased by expansion of the coil bobbin. In this work, the sample coils wound on DFRP bobbin and stainless steel (SUS) bobbin were prepared. The sample coil voltages were measured during increasing current in back ground external field. The coil using SUS bobbin showed many sharp peaks in tap voltage induced by quick wire motions. In contrast, those using DFRP bobbin showed no peaks. These results suggest that the quick wire motions were constrained by DFRP bobbin that had negative thermal expansion coefficient and low frictional coefficient.
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Tetsumi YURI, Toshio OGATA, Yoshinori ONO
Article type: Article
Pages
21-22
Published: September 20, 2002
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The high-cycle fatigue properties of Ti-5Al-2.5Sn ELI alloys and the effects of surface roughness and notch on their fatigue properties were investigated at cryogenic temperatures. Surface roughness of specimens was changed by different SiC paper (Grade #600,#100) and notched specimens (Kt=1.5,3) were prepared. The S-N curves shifted to higher stress level or longer life side with a decrease of the test temperature. Regarding the effect of surface roughness, the fatigue strength of the Grade #100-surface-roughness specimens were a little bit lower than those of Grade #600-surface-roughness specimens. Fatigue crack initiation sites of each surface roughness specimen at 4 K were at specimen interior. Using root area analysis, which is the size of the crack propagation plane as a shape parameter, the fatigue strength depends on the √area size. In notched specimens, the fatigue strength of the Kt=3 specimens were lower than those of the Kt=1.5 notched specimens. Although fatigue crack initiation sites of the Kt=3 notched specimens were at the notch root, those of the Kt=1.5 notched specimens were at specimen interior.
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Yoko YAMAGUCHI, Katsumi HORIGUCHI, Yasuhide SHINDO, Daisuke SEKIYA, Su ...
Article type: Article
Pages
23-24
Published: September 20, 2002
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This paper presents results from an analytical and experimental study of the effect of magnetic fields on the fracture properties in a nickel-iron superalloy (Incoloy 908). The tensile, notch tensile and small punch tests were employed at liquid helium temperature (4 K) in magnetic fields of 0 and 6 T (T; tesla). A finite element analysis were also preformed to convert the experimentally measured load-displacement data into useful engineering information.
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Yoshinori ONO, Toshihiro TSUCHIYAMA, Setsuo TAKAKI
Article type: Article
Pages
25-26
Published: September 20, 2002
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High manganese austenitic steel, for example Hadfield steel (13%Mn-1%C), exhibit ductile-to-brittle transition behavior related to intergranular fracture at low temperature. In this study, the influence of manganese content on low temperature toughness and fracture behavior has been investigated in high carbon and high manganese austenitic steel by means of electron microscopy, Charpy impact test and tensile test. Optimum manganese content for 0.9%C steel is 18 to 22 % to suppress the intergranular fracture and keep excellent toughness even at 77K. TEM observations of tensile-tested pieces have revealed that twin deformation, which causes stress concentration at grain boundaries, occurs also in 22%Mn-0.9%C steel as same as in Hadfield steel. This result suggests that the suppression of the intergranular fracture in 22% Mn-0.9% steel is due to the higher grain-boundary fracture strength of 22% Mn-0.9% steel than that of Hadfield steel.
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Toshio OGATA, Tetsumi YURI, Yoshinori ONO
Article type: Article
Pages
27-28
Published: September 20, 2002
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Local fracture toughness of top, middle, bottom, and heat-affected zones of weld joints of SUS304L and SUS316L have been evaluated by a new testing procedure of J-evaluation on tensile test (JETT) with circumferentially notched round bar specimen. Delta (δ)-ferrite contents of those welds were changed between 0% and 10%. The tests were carried out at 4K. Fracture toughness at 4 K obtained by JEIT was a little bit higher than that obtained by conventional CT specimens as was lower in weld metals than in base metals and decreased as the content of δ-ferrite increased in both 304L and 316L. Scatter in the values of fracture toughness among the locations in weld metals were considered to be caused by effects of δ-ferrite grains.
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S. Toyooka, Madjarova V., H. Kadono
Article type: Article
Pages
29-30
Published: September 20, 2002
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Electronic Speckle Pattern Interferometry (ESPI) has been developed to make possible to observe dynamic feature of deformation in Dynamic ESPI (DESPI). Precise phase analysis of "subtraction and addition method (SAM) is presented. Plastic deformation process of aluminum alloy (A2017) was analyzed. We found that there are two different features of the plastic deformation process. In the former process, plastic deformation is accompanied by vibration caused by strong energy concentration and relaxation. In the later process, switching between two quasi-stable states was observed frequently. These phenomena will be interpreted by Physical Mesomechanics (PMM)
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Koji YAMADA, Satoru TOYOOKA
Article type: Article
Pages
31-32
Published: September 20, 2002
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The Magnetic diagnosis of iron-based materials is performed by using a small Hall element for the leakage flux observation after polarizations of these materials. We found first derivatives of the normal component of the leakage flux along with the positions well coincided with intensities of residual strains for samples of SUS304,A533B and S25c, where the intensities of the first derivative in reversed proportional for paramagnetic amterial of SUS304 due to induced martensitic transformations and positively proportional for ferromagnetic materials of A533B and S25C.
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Manabu TOMINAGA, Satoru TOYOOKA, Koji YAMADA, Akiyoshi SHINAGAWA, Tosh ...
Article type: Article
Pages
33-34
Published: September 20, 2002
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Dynamic processes in tensile tests of SUS304 specimen were observed by dynamic ESPI that enables us to investigate the entire process of whole-field deformation. In later process of a plastic deformation state, we found that strain-localized band revealed by concentrated correlation fringes swept over the specimen repeatedly. Correspondingly, on the stress-strain curve, serrated variations took place. This phenomenon will be discussed associated strain-induced martensitic transformation.
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Kensuke KAGEYAMA, Youhei HARADA, Takeshi YOSHIKAWA, Hiroshi KATO
Article type: Article
Pages
35-36
Published: September 20, 2002
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Several agglomerated alumina powders were prepared and mixed with zirconia or zirconia rich virgin powder. Mixed powder were pressed and sintered by atmospheric sintering. Obtained specimens were served for four-point bending test and fracture toughness testing to investigate the influence of agglomerated structure on mechanical properties. SEM observation showed that the agglomerated alumina structures were dispersed in zlrconia rich matrix of all specimens. Some specimens also showed higher bending strength and/or fracture toughness than conventional alumina-zirconia composites.
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Takayuki SUZUKI, Kohei NAGATANI, Kazumi HIRANO, Tokuo TERAMOTO, Minoru ...
Article type: Article
Pages
37-38
Published: September 20, 2002
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Martensitic transformation and degradation characteristics for Fe-Pd ferromagnetic shape memory alloy were investigated by the developed AFM (Atomic Force Microscopy)/MFM (Magnetic Force Microscopy) hybrid nano-characterization technique. Martensitic transformation characteristics such as martensitic transformation temperature, reverse transformation temperature and morphology of martensitic phase for Fe-Pd alloy were detected by the changes in AFM and MFM images at microscopic or nanoscopic area. Degradation characteristics under cyclic loading at room temperature were also detected by the changes in AFM and MFM images. Especially in MFM the images became unfocused with increasing number of cycles although average martensitic transformation temperature changed slightly. Then it was found that the hybrid nano-characterization was high-sensitive technique to detect degradation under cyclic loading for ferromagnetic shape memory alloy.
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Qiuping Hu, Katsuhiko Watanabe
Article type: Article
Pages
39-40
Published: September 20, 2002
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Although it is known that the stress field in dissimilar materials under specified surface tractions generally depends on three independent elastic parameters, what three concrete parameters are useful and effective has yet to be studied. The authors showed previously that the axisymmetric problem is a special case of 3-dimensional problem of which the stress field depends on three elastic parameters and (α, β, γ) (α, β : Dundur's parameter, γ : product of two Poisson's ratios) is a useful combination of elastic parameters to deal with the problem, and proposed to use (α, β, γ)as parameters also for general 3-dimensional problem. In this paper, the fundamental properties of (α, β, γ) are studied and it is shown that these parameters exist in the closed domain in the 3-dimensional space of (α, β, γ).
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Qiuping Hu, Katsuhiko Watanabe
Article type: Article
Pages
41-42
Published: September 20, 2002
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The distinction between good pair and bad pair about the stress singularity at the interface edge for axisymmetric dissimilar materials can be made in the same way as in plane strain problems by Dundurs' parameters. However, the authors pointed out previously that, different from plane strain problems, the stress concentration at the interface may occur in the case of axisymmetric problems. In this report, the distinction conditions about the stress concentration are given by applying elastic parameter (α, β, γ) proposed previously and its validity is demonstrated through finite element analysis.
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Qiuping Hu, Katsuhiko Watanabe
Article type: Article
Pages
43-44
Published: September 20, 2002
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This study purports to derive fundamental solution of stress for 2-dimensional semi-infinite dissimilar materials. In this report, what elastic parameters are convenient and effective to specify material combination and to express the solution is discussed first. Then, the replacement of concentrated force in a body by traction force on virtual boundary, which is employed to obtain the solution, is introduced as the preparation for successive reports.
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Toshimitsu A. Yokobori, Izumi Jyohichi, Tadao Iwadate
Article type: Article
Pages
45-46
Published: September 20, 2002
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With regard to fracture under dynamic load, an interaction model in the form of a fracture model of a crack and a inverse pile-up of dynamic dislocation groups at the tip of a dislocation free zone was proposed. It was analysed based on a coexisting model of static equilibrium and dynamic distribution of dislocation arrays. These analyses showed that the stress concentration at a crack tip is reduced by the shielding effect of dislocation groups and that at the tip of the dislocation free zone is induced by the effective stress distribution in a dislocation array which is a result of the dynamic dislocation distribution. This result shows a theoretical foundation for the experimental result of the existence of a fracture trigger point under dynamic load.
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Hiroyuki HIRAKATA, Takato KUSANO, Takayuki KITAMURA
Article type: Article
Pages
47-48
Published: September 20, 2002
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A new technique for producing a sharp pre-crack at an interface between a thin film and a substrate ahs been developed and used for a sputtered Copper (Cu) thin film on Silicon (Si) substrate. In this technique, a vacuum evaporated Cu thin film, which has poor adhesion to Si, is inserted between the sputtered Cu thin film and the Si substrate as a release layer. The interface between the release layer and the Si substrate is debonded at a much lower load than needed for full debonding, or the sharp pre-crack is successfully produced. By loading continuously, the crack propagation test from the pre-crack tip is conducted, and the interface toughness, Gc, is evaluated as about 1.90J/m^2.
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Gakuji NAGAI, Takuya OHKUBO, Takahiro YAMADA, Katsuhiko WATANABE
Article type: Article
Pages
49-50
Published: September 20, 2002
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We have been developing an image-based 3-D finite element procedure for simulating the mechanical behaviors of concrete materials subjected to compression. On the assumption that concrete materials consist of coarse aggregates and mortar, the digital image captured from a physical concrete specimen is directly used as a finite element mesh. In this modeling, tensile failures on interface on interface between coarse aggregate and mortar are considered.
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Shojiro OCHIAI, Hirokazu TANAKA, Mototsugu TANAKA, Masaki HOJO, Hirosh ...
Article type: Article
Pages
51-52
Published: September 20, 2002
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For description of the tensile behavior of UD composites, a nondimesional shear lag method combined with a Monte Carlo simulation procedure was proposed. The proposed method was applied to microcomposite with different interfacial toughness. The variations of the damage map, stress-strain curve and fracture morphology with varying interfacial toughness could be described systematically.
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Yoshihiko HANGAI, Katsuhiko WATANABE
Article type: Article
Pages
53-54
Published: September 20, 2002
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This paper purports to study the possibility of compounded mesh pattern for evaluating the singularities in three-dimensional dissimilar materials. Because of the plural singularities in those materials, it is generally not easy to make a mesh pattern that can correspond to all of the singularities. To solve this problem, it is tried to use a compounded mesh pattern of two different mesh patterns. One is for one singularity and the other for the other singularity. The displacements for each mesh pattern are superposed. The formulation corresponding to finite element method is given based on the principle of virtual work and the applicability of the method is studied through numerical examples of interface edge problems.
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Yoshihiko HANGAI, Katsuhiko WATANABE
Article type: Article
Pages
55-56
Published: September 20, 2002
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In the first report, the formulation of the compounded mesh method was given, and the applicability of the method was studied through numerical examples of interface edge problems. In this paper, three-dimensional center-through interface crack model is studied. Two mesh patterns are prepared. One mesh pattern is for the crack singularity and the other mesh is for interface edge singularity. These two mesh patterns are compounded, and the applicability of this method is studied.
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Toru KAWAGUCHI, Yoshihumi HIROSAWA, Masaki HOJO, Mototsugu TANAKA, Sho ...
Article type: Article
Pages
57-58
Published: September 20, 2002
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Single notched model composites, which consisted of boron fibers and the transparent epoxy resin, were used to observe the microscopic fracture process of unidirectional fiber-reinforced plastics during tensile testing. Tests were carried out under static loading. The in-situ observation revealed the typical fracture process as follows : First, matrix crack initiated at the notch tip and the crack growth was arrested by the neighboring fiber. Then, the onset and growth of interfacial debonding was observed while the main matrix crack was stable. The matrix crack growth and the interfacial debonding were repeated alternatively followed by the final overall fracture of the model composites. The three dimensional finite element analysis was carried out based on the in-situ observation. The observed fracture process was well reproduced and the values of the interfacial fracture toughness were evaluated.
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Mototsugu TANAKA, Akinori KONO, Masaki HOJO, Shojiro OCHIAI
Article type: Article
Pages
59-60
Published: September 20, 2002
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The finite element analysis was carried on in order to clarify the microscopic fracture mechanism of the matrix resin layer of FRP at the crack tip under the mode II loading. The analysis revealed the fracture process as follows : First, the microcrack initiated at the main crack tip due to the principal stress. Subsequent microcracks occurred one after another at even intervals with the increasing shear loading. Then, the delamination of the interface between fibers and the matrix resin layer initiated around the last microcrack due to the shear stress. Finally, the connection of microcracks occurred from the last microcrack to the main crack tip. The effect of the thickness of the matrix resin layer on the interval of microcracks was also investigated. The interval of microcracks increased in proportion to the increase of the thickness of the matrix resin layer.
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Hiroyasu YAMAMOTO, Chunhung CHEN
Article type: Article
Pages
61-62
Published: September 20, 2002
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The tensor expression of Hill's anisotropic yield surface equation has been considered, and the elastic-plastic constitutive equation for anisotropic materials has been derived from its yield surface equation. Then, by applying this constitutive equation to the uniaxial tensile deformation, the equation for the size variation of tensile specimen has been obtained.
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Hiroyasu YAMAMOTO, Chunhung CHEN
Article type: Article
Pages
63-64
Published: September 20, 2002
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By applying the elastic-plastic constitutive equation based on Hill's anisotropic yield surface equation to the uniaxial tensile deformation, the size variation of tensile specimens has been numerically analyzed with the r-values as parameters of the material anisotropy. Then, the results of the numerical calculation have been compared with those of the uniaxial tensile test of carbon steel specimens. As a result, it has been shown that the accuracy of size variation of specimens in the numerical analysis improves remarkably by considering the material anisotropy.
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Yoshiaki YASUI, Daigoro SAITO, Mai MOCHIDA
Article type: Article
Pages
65-66
Published: September 20, 2002
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This paper presents the impact absorbing characteristics of aluminum honeycomb cell under axial impact loading. In order to clarify dynamic impact absorbing characteristics of honeycomb structure generally used as lightweight structure member, following facts were executed on enlarged hexagonal cell mode. For the purpose of the increasing of energy absorption quantity multi-layered cell model were performed dynamic test by dropped hammer impact test machine and FEM analysis about honeycomb increased of the multi-layered number and it changed the ratio of upper cell (h_U) and bottom cell's (h_B) height. As the result of experimental and analytical studies, the fundamental impact absorbing characteristics was able to confirmed multi-layered cell models honeycomb cell. And, 2layered honeycomb cell proved effectiveness that it is not retated to influence by shape or figure.
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Futoshi NISHIMURA, Kazuhiro MORINO, Norio KAWAGOISHI, Kazunori FUKADA
Article type: Article
Pages
67-68
Published: September 20, 2002
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In this study, tensile tests were carried out on four kinds of high-strength steels by radical nitriding (Die steel; SKD61,Maraging steel; YAG300,Structural steel; SNCM439 and High carbon chromium bearing steel; SUJ2). The influence of nitriding on stress-strain behavior and mechanical properties were investigated. As a result, fracture ductility of these materials was decreased by nitriding. The decrease of fracture ductility was related to the crack occurrence on specimen surface. On the nitrided steel, the main reason for the decrease of fracture ductility was surface embrittlement due to nitriding.
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Youhei YAMAIZUMI, Noriaki OKAMOTO, Mituhiro SHINBORI, [in Japanese]
Article type: Article
Pages
69-70
Published: September 20, 2002
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Experiments were performed to study the behavior of axially crushed aluminum round tubes. The mean radius to thickness (R/h) ratios of these varied from 15 to 75. The modes of collapse and the mean collapse loads obtained in these tests are presented. A simple estimation on the energy-absorption efficiency is presented by using the buckling stress expression based on the tangent modulus theory and the expression of mean collapse load considering the formation of plastic hinges. The estimation results are compared with the experiments.
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Shinji KUBO, Takeshi IWAMOTO, Toshio TSUTA
Article type: Article
Pages
71-72
Published: September 20, 2002
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At present, there are a lot of research works evaluating the deformation behavior of metallic materials by crystal plasticity theory in order to account for their microscopic deformation behavior in crystal level. Of course, the influence of martensitic transformation on TRIP steel must be taken into account because martensite is formed with the specific crystal orientation relationship between parent phase and martensite. Moreover, the martensitic transformation affects greatly the mechanical properties of TRIP steel. Here, the coupled effects of slip systems and variant systems on the martensitic transformation process and the mechanical properties of TRIP steel are investigated. Therefore, the constitutive equation for single crystal is derived by including the influence of the martensitic transformation into the usual crystal plasticity theory Then, the deformation behavior under plane strain condition is simulated by FEM.
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Yuji Nakasone, Tetsu Shimizu, Soji Kasumi, Daisuke Tabata, Hisashi Bep ...
Article type: Article
Pages
73-74
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The present study has investigated plasticity-induced martensitic phase transformation in fatigue of unnotched SUS304 plates. Martensitic phase transformation occurred in uunotched SUS304 plate specimens fatigued at room temperature in air. Volume fraction ξ_<α'> of α' martensite in the uunotched potion of fatigued specimens was measured by ferrite scope. The relations between the maximum value of ξ_<α'>, ξ_<α'max>, and the number of load cycles N were represented by reverse sigmoidal curves for all the applied stress range △σ levels tested in this study. For the most portion of fatigue life, the value ofξ_<α'max> remained almost constant. This value was increased with increase in the value of △σ. The spatial distribution ofξ_<α'> in the specimens varied with N : i.e., continued cycling of stress made α' transformation localized near the central portion of specimens where the ξ_<α'>, value reached as high as 30-40%. This value is more than doubled compared to the highest ξ_<α'> value found in the tensile tests of SUS304 at room temperature. Invisible cracks of 200μm in length were found in the high ξ_<α'> value region. These results imply that the measurement of ξ_<α'> in fatigued SUS304 components may detect crack initiation sites and may predict residual fatigue life.
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Tomomi NAKAJIMA, Osamu WATANABE
Article type: Article
Pages
75-76
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Crack initiation and propagation of fcc polycrystal are studied from the mesoscopic viewpoint. OFHC copper, pure aluminum and SUS 304 stainless steel are taken as examples of material fracture to observe surface under both of monotonic and cyclic loadings. Crack initiation and propagation is simulated based on Asaro's crystal plasticity model by introducing fracture mechanism in finite elements reacting mesoscopic stress or strain at the fracture boundary surface. The obtained results may be regarded as physically plausible, and they are examined and compared with experimental results.
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Masashi SHIBATA, Mitsutoshi KURODA
Article type: Article
Pages
77-78
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Continuum damage mechanics has been used in a number of creep analyzes. Various material constants in theories of continuum damage mechanics are determined so that the predictions agree with experimental results. Physical meaning of such material constants are not necessarily clear. In this study, we use a micromechanical approach to evaluate a damage variable in continuum damage mechanics.
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Kazuhito SHINTANI, Takaaki NAKAJIMA, Kouta YAMAYA
Article type: Article
Pages
79-80
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Since a linear strand of gold atoms was observed at a nanocontact between a STM probe and a metal surface, nanowires of metals and semiconductors have drawn much attention of researchers working in the field of nanotechnologies. Nanowires are expected to show both the electronic and mechanical properties peculiar to nanoscale. In this study, molecular dynamics simulation is employed to study deformations of gold nanowires under tensile strain. The interaction forces between atoms are calculated by using the embedded-atom method potential. Before tensile process, the model nanowire is equilibrated at a specified temperature. While a few layers at one end of the nanowire are kept fixed, the ones at the opposite end are forced to be displaced. How the anisotropy of the nanowires affects their deformation behaviours and mechanical properties is investigated.
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Tetsuya OHASHI, Michihiro SATO, Akihito UMANO, Takuya MARUIZUMI, Isao ...
Article type: Article
Pages
81-82
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The periodic structure of the shallow trench isolation (STI) type ULSI cells is generally used for the latest semiconductor device structure. However, dislocations are accumulated when the device size becomes small, and in the electron channel they have an enormous effect on the electronic state and obstruct the device from normal operation. In this paper, we model the periodic structure of the STI type ULSI cells, and analyze plastic slip that takes place in the devices during the oxidation process of oxide film and evaluate the accumulation of dislocations that accompany plastic slip. For the analysis of slip deformation, we use a crystal plasticity analysis program which is based on the finite element technique. The result shows that stress concentrations at the shoulder part of the device area and bottom corner of trench cause plastic slip and dislocation accumulation, and directions of these dislocation lines are mostly parallel to z axis and this means that these dislocations are approximately 60°mixed type.
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Shi hua TANG, Michiaki KOBAYASHI, Setsuo MIURA, Hiroyuki FUJIKI, Seiic ...
Article type: Article
Pages
83-84
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In the authors' series study on ultrasonic nondestructive evaluation method, longitudinal wave velocities propagating in the plastically deformed medium under simple and pure shear states were apparently different from each other. The investigation has suggested that the point defects induced by cross slip were one of the major reasons to cause such differences. As one of studies on this phenomenon, the current paper will present the authors extended investigation on how the surface morphology, i.e. surface roughness is developed under both shear states via finite element polycrystal model. Finally, the authors will also give a quantitative analysis on the irregularity of surface roughness via fractional dimensional analysis.
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Ryoichi KAWAKAMI, Shoji IMATANI
Article type: Article
Pages
85-86
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Poly crystalline materials are composed of crystal grains, each of which is joined with neighboring grain via so-called grain boundary. The grain boundary is supposed to play a major role in the deformation behavior at high temperature. This paper deals with the three dimensional finite element analysis of such poly crystals. A single crystal model proposed by Asaro is employed in each crystal and grain boundary sliding is also taken in account. It is shown that the local deformation is relaxed due to the grain boundary sliding and that the geometrical configuration of grain boundary is dominant on the inhomogeneous deformation of the poly crystal material model.
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Tsuyoshi MAYAMA, Katsuhiko SASAKI, Hiromasa ISHIKAWA
Article type: Article
Pages
87-88
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In this study, a series of subsequent creep tests and microscopic observations were carried out at room temperature. Creep curves after cyclic preloading on SUS304 stainless steel had the dependence of the cycle number of the cyclic loading. Microscopic observations were also conducted by TEM to confirm the dependence of the creep curves on the cycle number. The microscopic observation showed that dislocation structures changed due to the additional cyclic loading after stress-strain relation stabilized. Finally considering dislocation density creep curves were described by Boyle-Spence type creep law.
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Hiroshi OKADA, Yasuyoshi FUKUI, Noriyoshi KUMAZAWA
Article type: Article
Pages
89-90
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Micromechanical analyses on rubber modified epoxy resin are presented. In rubber modified epoxy resin, rubber particles are contained in Epoxy matrix. Epoxy can be regarded as a brittle matrix material and dose not undergo much nonlinear deformation. It has been seen in literature that Epoxy undergoes a considerable amount of nonlinear deformation when it is mixed with rubber. Such a material is called rubber modified Epoxy resin. It has also pointed out in literature that the primary cause of nonlinear deformation is the cavitations (fracture) of rubber particles which are embedded in Epoxy matrix. In this paper, we point out that that the effects of residual stress which is induced in curing process has a significant contributions in the deformation mechanisms of rubber modified Epoxy resin. Analyses are carried out using a classical method of micromechanics and a BE (boundary element) based homogenization method.
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Yusuke HANDA, Mitsutoshi KURODA
Article type: Article
Pages
91-92
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A polymer blend containing a large number of small rubber particles shows much higher toughness in comparison to non-blend polymer. In this study, we study microscopic deformation behavior in a polymer blend using finite element analysis. Furthermore, a macroscopic constitutive model that represents observations in the microscopic analysis is proposed. This macroscopic constitutive model is suitable for large-scale engineering computation.
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Seiichi KOBAYASHI, Daisuke Tomii, Toshikazu TORIGAKI, Kazuyuki SHIZAWA
Article type: Article
Pages
93-94
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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An investigation of theoretical modeling and numerical simulation for polymer such as polypropylene or ABS resin is expected for its industrial application under conditions of large deformation, high strain rate and failure of a structure. In this report, constitutive equations of non-coaxial viscoplasticity and of craze as a damage in polymer are thermodynamically derived by considering anisotropic craze evolution with plastic deformation. Also a transformation rule of craze tensor between damage and pseudo non-damage configurations is newly proposed. Then influences of damage evolution around a shear band to Young's modulus and effective stress are numerically discussed through a large deformation FEM analysis.
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