This paper describes a through-wall crack length evaluation procedure applicable to Leak Before Break (LBB) assessment of Japan Sodium cooled Fast Reactor (JSFR) pipes made of Mod.9Cr-1Mo steel. In LBB assessment of JSFR pipes, it is required to calculate virtual through-wall crack length, though the crack growth is quite small under design condition. Generally, it is known that the through-wall crack length depends on loading condition, namely the load ratio between tensile and bending and that the length under pure bending load condition is largest. This study proposes a simplified method to evaluate the through-wall crack length both for axial and circumferential cracks as a function of load ratio and fatigue crack growth characteristics. Using the method, through-wall crack length can be predicted as far as we know the loading condition and material properties.

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配管は、社会インフラの水、ガスから、産業界での油圧、薬品、反応ガス…など、あらゆる分野に使われており、これらの特に締結部の漏れ等の耐久性確保は、社会・プラント・設備全体の安全性確保の上で非常に重要な技術課題となってきている。本報告はこれら配管継ぎ手の中でも産業界で広く用いられているくい込み型鋼管継手(Bite Type Tube Fittings)を対象に、繰返し内圧、曲げ振動、負荷下でのねじ締結部位の力学敵挙動解析、ゆるみ評価を行い、ねじ嵌めあい面でのすべり発生に基づいた簡易ゆるみ限界基準を導いた。これらの基準予測式の妥当性を確認するために、各種不可の繰返し試験を行い、ゆるみ等の実測から予測式の妥当性を確認した。

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The numerical simulation was carried out for the Erichsen test of 6000 series aluminum alloy plate with a large scale parallel computing finite element method, ADVENTURE Cluster[○!R]. Stress and strain distributions in the test piece were obtained in detail. It was shown that necking was occurred at the circle which is about 30° from the top of the punch rod and the necking was decided the Erichsen value.

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In order to examine the sealing mechanism of a connection with a metal gasket, the sealing test according to JIS B2490 and FEM analysis were carried out. The dimensions of platen used in the test are according to JIS B 2490 and the metal gasket types are chosen as metal flat and ring joint gasket. The material of the gaskets was aluminum. The ring joint gasket types are chosen as octagonal and oval. The effect of internal pressure on the sealing performance of connection with the metal flat gaskets was measured. The relationship between the gasket compression stress and amount of leakage through inter faces on the metal flat gasket was obtained. And also, the relationship between compression load and amount of leakage through inter faces on the ring joint gaskets was obtained. The von Mises stress distributions on the interface on the metal gaskets were calculated using FEM. Using the results of sealing test and FEM, it was suggested that the sealing performance was improved, when the von Mises stress more than the gaskets material of the yield stress adequately. Furthermore, it was suggested experimentally that the ratio of the maximum of von Mises stress in the gaskets material of yield stress was 1.015.

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We derive a solution for two elliptical voids that are free boundary to an elastic medium (matrix) of infinite extent under anti-plane problem. These two voids have different long and short radii and different central points. When there are two voids in the matrix, we consider the matrix as a part of poroelastic matrix. The matrix is subjected to arbitrary loading, for example, by uniform stresses. The solution is obtained as a series with an explicit general term involving the complex potential of the corresponding homogeneous problem. This procedure is referred to as heterogenization. Several numerical examples are presented with graphs.

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Regarding bending buckling of box beams which have the rectangular cross-section with four thin plates, we try to derive the buckling stress based on the energy method. Box beams of the main target are with the aspect ratio of cross-section accompanied with compression buckling in the compressed plate. It is supposed that the buckling occurs only at the compression side and forced displacement at two adjacent plates is induced by the compression buckling. The accuracy of the derived equation is verified by the comparison with the results of buckling eigenvalue analysis using Finite Element Method (FEM). The derived buckling stresses correspond to results by FEM, although somewhat error exists near the critical aspect ratio of the cross-section.

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This paper describes the relation between the flattening phenomenon in the cross section and the visco-elastic behavior of the catheter made of soft nylon resin which is reinforced with thin stainless wires called braid. Especially, by considering that the shape of cross section gradually changes into the elliptical shape during process of applying the torsional moment, the experimental formula for the torsional moment is derived based on the shear flow theory, and then, the values of torque when the flattening phenomenon begin to start are estimated. Moreover, in this study, in order to confirm the effect of axial force on the flattening phenomenon, the experiments are conducted under conditions that the initial axial force is variously changed.

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Scoliosis is a disease in which the spine is curved to the lateral. Surgery is the only way to revert from serious scoliosis to normal spinal array. Metallic implant is used in scoliosis surgery to correct the spine array. The spinal implant is composed of a plurality of components such as rod, connector and screw. However, the implant installed would be sometimes broken in everyday life. In this study, the implant model is recreated in the CAD system, to perform stress analysis by the finite element method. It is clarified that the absolute value of the longitudinal compressive stress increases at the edge portion of the slit of the connector and the tensile stress increases at the central portion of the connector side closer to the vertebra.

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The purpose of this study is to investigate the development of local deformation by using the image analysis based on Natural strain theory. In our previous study, the local deformations generated under different types of deformations history, which are obtained by applying the simple shear to the reversed direction after the forward direction, have been examined. It is confirmed that the development of local deformation is almost the same if sum of the strain that is obtained by the different deformation path is the same. The developments of local deformation in each infinitesimal element on the surface of the specimens are investigated under the condition that the plastic strain on identical line elements is integrated along each deformation path. In this study, the developments of local deformation in the simple shear after applying the initial tension are examined. Then, the effect of pre-tensile deformation on the development of local deformation generated under large shear is revealed.

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The purpose of this study is to investigate the relation between the development of anisotropy and the deformation history of pre-deformation by examining the shape of yield surface obtained under large deformation. In a series of our previous reports, using a test piece applying the large pre-deformation of the combined loading of tension and shear, the shape of yield surface has been estimated by investigating the slope of the tangent in the deviatoric stress and deviatoric strain curves. In this paper, the shape of yield surface is examined by conducting the experiment for changing the sequence of tension and torsion in pre-deformation. Especially, the pre-deformation of shear after uni-axial tension is investigated in this report. Then, the relation between the development of the anisotropy of yield surface and the deformation history of the pre-deformation are revealed.

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In experimental measurement, displacements at top of the membrane have been measured by laser displacement meter. Large deformation and contact simulations were performed to study deformation behavior of membrane by using a large scale simulator ADVENTURECluster^[○!R] which was based on Finite Element Method (FEM). Both cases of simulation and experiment, two types of tensions of 0.5kN/m and 1kN/m were loaded on the edge of membrane to compare experimental displacement measurements and simulation results. In this study, the problems that we should consider to establish design technique have been shown from simulations and experimental displacement measurement.

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Nominal structural stress (NSS) is one of the parameter for the fatigue life prediction method of the spot welded structure. There is the calculation method for accurately obtaining the nominal structural stress. In this study, the NSS calculation method was applied to the arc-weld test specimen, the position that nominal structural stress occurs was obtained. The position of fatigue failure was confirmed by the fatigue experiments. The possibility that the position of fatigue failure is obtained by nominal structural stress was shown.

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Recently, a development of the fatigue life prediction technology of the weld by CAE is demanded. In our previous researches, the nominal structural stress (NSS) calculation method was applied to the arc-weld structure, it has been shown that there is a possibility of predicting the fatigue life of an arc welding. In this study, the NSS calculation method of arc weld structure was applied to the laser weld structure, the accuracy of stress values which was obtained from the NSS calculation method was researched. As a result, the nominal structural stress of the laser weld structure was accurately obtained by the NSS calculation method.

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In welding, material is heating locally. Therefore, it generates tensile residual stress in the heat affected zone and changes the quality of material. Those will be causes problem of stress corrosion cracking in SUS304. One of the conventional prevention is to use material that hardly occur heat sensitization, but stress corrosion cracking is observed in that material. Therefore, it is desired to reduce or remove the tensile residual stress generated by welding. Accordingly, we have been proposed a method that adds ultrasonic vibration during welding. The method can reduce the tensile residual stress easily in a shorter time than conventional methods. Experimentally, it has ever been shown that this method can reduce the tensile residual stress on heated zone for thin plate of SUS304. In this study, it is examined that acceleration amplitude influences to reduction of the tensile residual stress for welding of thin plate of SUS304.

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Sharp resonance response is important for many micrometer- and nanometer-scale resonators used in MEMS and NEMS. The purpose of the present paper is to numerically analyze thermoelastic damping of micro-scale resonators using the elastodynamic finite integration technique (EFIT) for coupling problems of elastodynamics and heat conduction. We analyze the damping behavior of a cantilever-type resonator for different aspect ratios. It is found that the peak magnitude of thermoelastic damping decreases for higher aspect ratio of the resonator. The numerical results are also compared to the theoretical prediction based on the Bernoulli-Euler beam theory.

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In order to evaluate the fatigue strength of the machine structures, it is necessary to know the fatigue crack propagation properties. Conventionally, a replica method has been used to observe the fatigue crack propagation properties. However, a lot of time and trouble are taken with copying the fatigue crack shape down from the specimen surface. Thus, real-time fatigue crack observation system for a rotating bending fatigue testing machine has been newly developed in this study. The purpose of this study is to investigate the fatigue crack propagation properties of JIS SCM435 under very high cycle regime by using the newly developed system.

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Low- and high-cycle fatigue tests were conducted for heats A and B of SUS630 stainless steels. 480℃ (H900) and 580℃ (H1075) aging samples were prepared. In the low-cycle fatigue properties, all samples revealed almost equal fatigue strength under constant strain amplitude tests. Cyclic softening and hardening were small, and cyclic yield stress was higher than conventional steels. In the high-cycle fatigue tests, almost all specimens showed internal fracture in case of H900, while H1075 showed surface and internal fractures in short and long life regions, respectively. In the high-cycle fatigue properties, although the heat A revealed higher fatigue strength than the heat B, the difference was small between the H900 and H1075. The high-cycle fatigue strength of the present materials was lower than that of other high-strength steel in spite of almost equal inclusion sizes.

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Internal fatigue crack growth rate was measured by using beach marks resulting from repeated two-step fatigue tests. Two types of b each marks were then observed, which were small and large beach marks indicating internal cracks at initial and final stages of fatigue, respectively. The internal crack shape at the initial stage was a half-ellipse and asymmetric, while that at the final stage were a circle and symmetric. The asymmetric internal crack shape requires three-dimensional modeling, and therefore, an extremely slow crack growth rate, smaller than the lattice length, is expected in two-dimensional modeling. The asymmetric internal crack actually revealed the extremely slow crack growth rate. Moreover, the measured growth rate showed good agreements with that estimated by Omata's method based on Tanaka-Akiniwa model. These results indicate that the gigacycle fatigue life can be estimated by the internal small crack growth life.

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In this study, Giga-cycle fatigue properties for A5083P-O aluminum alloy were investigated by ultrasonic fatigue testing at 20 kHz, rotating bending fatigue testing at 100Hz and electromagnetic resonance type fatigue testing at 100 Hz. Not only the ultrasonic fatigue testing but also rotating bending fatigue testing were conducted up to 10^<10> cycles with 3 years testing period to validate the ultrasonic fatigue testing. The results of the ultrasonic fatigue test showed negligible difference from those of conventional fatigue testing results. Furthermore the slope of S-N curve becomes smaller in 10^8〜10^<10> cycles and fatigue limit like behavior was discovered. In addition, successive surface observation result indicated that non-propagating fatigue crack related to fatigue limit existing.

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A three dimensional grain mapping technique for polycrystalline materials, called X-ray diffraction contrast tomography (DCT), was developed at SPring-8 (Super Photon ring-8 GeV), which is the brightest synchrotron radiation facility in Japan. To evaluate the fatigue damage of grains, total misorientation, β for each grain was calculated from DCT measurement. It is found that value of β increases with number of cycles, and change of β for primary slip plane is the largest in diffraction planes. In addition, the largest change of β, was observed in the diffraction plane with the largest Schmid factor, F_s in equivalent primary slip planes. From this results, it is found that change of β reflects slip behavior in a grain, because change of β correspond to Schmid factor in fcc materials which can be determined the primary slip direction.

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In the present study, fatigue fracture behavior of commercially pure iron thin wires with the grain size of 23 μm and the diameter of 700μm was investigated by bending fatigue test. At bending moment ratio M_<min>/M_<max>=-1 and -0.8, microscopic observation of fracture surface shows striations. Therefore fatigue cracks initiated at both the upper and lower surfaces and propagated toward the neutral axis of the specimen. On the other hand for tension-tension fatigue (stress ratio R=0.1), ratcheting failure and necking were occurred and the initiation and propagation of fatigue crack were not observed.

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The purpose of this study is to investigate low cycle fatigue (LCF) strength, crack initiation and crack growth behavior of Ni based superalloy Alloy246. As the result of the observation of etched specimen, grain size is from 3 to 5 mm. LCF test is conducted under load controlled conditions. Small cracks initiate at the first cycle of low cycle fatigue and grow with coalescence. Small cracks propagate along slip direction. The result of fracture mechanics evaluation shows crack growth rate along dendritic structure is higher than that along slip direction. As the result of EBSD, crack growth direction corresponds to slip plane. Small cracks initiate near grain boundary. Small cracks initiate under stress of 100 MPa.

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The high cycle fatigue properties of Fe-30Mn-3Si-3Al and Fe-22Mn-0.5C twinning-induced plasticity (TWIP) steels were evaluated by rotary bending fatigue testing and a replica technique. More specifically, small fatigue crack propagation and non-propagating fatigue crack phenomenon were comparatively studied in terms of occurrence of dynamic strain aging. In fact, dynamic strain aging occurs in the Fe-22Mn-0.5C TWIP steel because of the presence of Interstitial-substitutional (I-S) atom interactions. Probably due to the occurrence of dynamic strain aging, only the Fe-22Mn-0.5C TWIP steel showed non-propagating fatigue crack phenomenon at the fatigue limit. In contrast, a small fatigue crack of the Fe-30Mn-3Si-3Al TWIP steel continuously propagated even at the fatigue limit which was defined that the specimen does not fracture until 10^7 cycles.

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The spot weld of high tensile steel does not improve as base metal strength. However, with the application of high tensile steel by the body light weighting, the strength evaluation of the spot weld becomes important in a design. Therefore I perform the fatigue test of high tensile steel and spot welded joint and clarify control factor and a design guideline for the fatigue strength. As a result, I made clear that I could evaluate fatigue strength with a stress Intensity Factor mixed mode (mode I and mode II).

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The spot weld of high tensile steel does not improve as base metal strength. The previous study has investigated that a stress Intensity Factor mixed mode (mode I and mode II) can evaluate the fatigue strength. However, influence of residual stress is still not obvious which is important for the design of fatigue or spot weld conditions. Therefore, this study accomplish to clarify the fatigue limit diagram of notched specimen to evaluate fatigue strength of spot weld toe. Then, it become obvious that the compressive residual stress make extensive improvement of the fatigue strength.

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The spot weld of high tensile steel does not improve as base metal strength. However, with the application of high tensile steel by the body light weighting, the strength evaluation of the spot weld becomes important in a design. The previous studies show that a index to estimate fatigue strength and a possibility to improve fatigue strength. This study achieve extensive improvement of the fatigue strength by compressive residual stress that can apply to 590〜1500MPa grade steel. This improvement correspond to the estimation from the fatigue limit diagram of notched specimen.

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In this study, the fatigue properties of friction stir welded joint used A6061 and A2024 Aluminium alloys were evaluated. In order to consider the fatigue properties, fatigue tests were conducted at stress ratio R=-1, cyclic speed 23.3 Hz with plane bending fatigue condition. And then hardness distribution, fracture position, microstructure, crack growth behavior were investigated. As a result, hardness distribution and fracture position were corresponded in A2024 and A6061 FSW joints, but were not corresponded A6061/A2024 dissimilar FSW joint under the influence of microstructure. And surface crack growth behavior of A6061/A2024 dissimilar FSW joint showed same tendency of A6061 FSW joint. However, S-N behavior of A6061/A2024 dissimilar FSW joint showed same tendency of A2024 FSW joint. The reason for this, the influence of micro-crack growth behavior from crack initiation to 0.3mm.

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Materials containing columnar grains might cause fatigue life reduction. In this study, fatigue tests were carried out for nickel-based superalloy polycrystals, which were composed of (i) columnar grains + equiaxed grains and (ii) only equiaxed grains. Polycrystalline FE analyses were conducted to estimate their fatigue lives. Resolved shear stresses ware calculated in expected twelve slip systems by FE analysis. Fatigue life was estimated based on the resolved shear stresses on primary slip plane. It was suggested that there were fatigue life reduction in materials containing columnar grains by FE analysis, but there was no significant difference between the two materials by fatigue tests.

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In order to clarify the relationship between the microstructure and the small fatigue crack initiation behavior in Ti-6Al-4V alloy, the small fatigue crack initiated in Ti-6Al-4V alloy was observed in detail by using an atomic force microscopy (AFM) and an electron back scattered diffraction (EBSD). The fatigue crack in Ti-6Al-4V alloy initiated from the basal slip in a-phase. In addition, in comparison with Schmid factor of α-phase from which the fatigue crack initiated and other α-phases around the crack initiation area, Schmid factor in a-phase from which the fatigue crack initiated is the highest compared with other α-phases.

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In this study, the effect of low temperature nitriding on the 4-points bending fatigue properties of Ti-6Al-4V alloy were examined. The fatigue limit of the nitrided specimens tended to increase as the nitriding temperature decreased. Especially, the specimens nitrided at 550 ℃ showed higher fatigue limit than that of the un-nitrided specimen, whereas the conventional nitriding at 850 ℃ reduced the fatigue limit of Ti-6Al-4V alloy. This was because a thick nitrogen compound layer was formed and grain-coarsening occurred. Moreover, the fatigue crack propagation of the nitrided Ti-6Al-4V alloy was observed using the developed system.

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The effects of cavitation peening (CP) and shot peening (SP) on bending fatigue strengths of an aluminum alloy (A7075-T6) specimen with an artificial semi-circular slit were investigated The bending fatigue test specimens with small semi-circular slit were subjected to CP and SR Bending fatigue tests were conducted on the specimens to determine the fatigue strength and the depth of the semi-circular slit that can be rendered harmless by CP and SR It was found that the fatigue strength increased and a semi-circular slit less than 0.2 mm and 0.1 mm in depth was rendered harmless by CP and SP, respectively. The depth of a semi-circular slit that can be rendered harmless by CP and SP was estimated based on fracture mechanics assuming that the semi-circular slit was equivalent to a semi-circular crack The prediction results were almost consistent with the experimental results. These results indicated that the distribution of compressive residual stress is a controlling factor of the depth of the semi-circular slit that can be rendered harmless by peening.

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The effect of shot peening (SP) on rolling contact fatigue life of bearing steel JIS-SUJ2 under contaminated lubrication was investigated. Vickers hardness of the specimen were measured before and after SP. Resistance to indentations was compared by measuring the profiles of the Vickers indentation. Then, rolling contact fatigue tests were carried out under contaminated lubrication. The resistance to indentations and rolling contact fatigue life were improved by SP owing to work hardening and compressive residual stress. Thus, SP is effective in increasing the rolling contact fatigue life in contaminated lubrication.

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Fatigue crack initiation behavior of shot-peened magnesium alloy AZ31 was investigated. Fatigue tests were conducted using a rotary bending fatigue testing machine. The fatigue specimens were machined from two directions. Their loading directions are parallel and perpendicular to rolling direction. In the finite life regime, the shot peening improved the fatigue life significantly and the anisotropy in fatigue life disappeared by shot peening. On the other hand, fatigue limit of peened specimen was almost the same in comparison with that of untreated specimen. And the anisotropy in fatigue limit still remained. The crack initiation behaviors at stress amplitude of 115MPa were observed using an optical microscope. The small crack was initiated along the twin boundary at the early stage of fatigue life even in shot peened specimen. However, the crack growth was delayed by shot peening, resulting in the improvement of fatigue life in shot peened specimen.

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Zr_<55>Cu_<30>Ni_<30>Al_<10> bulk metallic glass (BMG) is known to show high strength. However, comparing with the strength of BMG, the fatigue limit observed under 4-points bending condition higher than espected. In addition, a fatigue crack usually initiates from a corner of the tensile stress surface. After fatigue tests, fracture surfaces were observed using a scanning electron microscope (SEM). As a result, the fracture surface includes two primary regions: a crack-growth region and a final-fracture region. The crack-fatigue region is spread in concentric circles from the fracture origin part and covered completely by striation-like stripes. In addition, the stripes were discussed with attention to the point that it matches the characteristics of the striations. According to the results, stripes observed in the fatigue fracture region suggested the possibility of striations.

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Two fundamental concepts for diagraming and formulating fatigue strength of notched materials are described; the hypothesis of cyclically plastic adaptation and the yield-zone-based criterion on size effect. Each concept is independently and has a quite different base. The former describes cyclic stress behavior at a fatigue slip band and is concreted as an equivalent cyclic stress ratio reflecting mean stress effect. The latter is formulated by normalizing a yield zone growth curve and ranked as a kind of a ductile failure rule combining with stress distribution. Based on such conceptions, the fatigue strength of the notched and un-notched specimen can be linked completely analytically. It is noted that, by utilizing formulae in plasticity on beams and torsion bars, the yield-zone-based criterion on size effect explains analytically and numerically the size effect of the un-notched specimen itself.

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Lots of accident for industrial structures are caused by material fatigue. In some situations, detection of fatigue crack are required to prevent catastrophic accident. The stopping hole method is used as countermeasure for detected cracks. The stopping hole that is introduced in crack tip restrain stress concentration, and fatigue crack growth is delayed. However, stopping hole diameter is not determined based on knowledge of fracture mechanics. In many cases, the diameter is determined by engineer's experience. Measurement based on mechanical consideration is fundamental to enhance the efficacy of stopping hole. Some fatigue crack growth experiments with stopping hole is demonstrated in this study. Introduction of stopping hole into closed two cracks situation and out-plane compress stress effects for fatigue crack are discussed based on the experimental results. Number of loading cycle to cause re-growth of fatigue crack is derived by the experiments, and stress concentration factor is calculated by finite element method based on the experimental conditions.

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A new ΔK-decreasing test method was developed by using metal film. The film was adhered to a through elliptical hole in a base plate and was fatigued in accordance with the displacement constraint along the hole circumference in the base plate subjected to a cyclic stress. Commonly, a stress intensity factor range was increased with a crack propagation under a constant stress amplitude but was decreased toward the hole edge because of the difference in thickness between the film and the base plate in this ΔK-decreasing test method. As a result, the fatigue crack propagation rate was decreased and was arrested near the hole edge under the constant stress amplitude to the base plate. The threshold stress intensity factor ranges were obtained for some kinds of metal films.

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The influence of fiber orientation on the crack propagation behavior was studied with single edge notched specimen which were cut from an injection molded plate of thermoplastic polyphenylenesulphitde (PPS) reinforced with 30wt% carbon fibers. Specimens were cut at five angles relative to the molding direction, i.e. θ=0°(MD), 22.5°, 45°, 67.5°, 90°(TD). Fracture mechanics parameters derived based on anisotropic elasticity were used as a crack driving force. Macroscopic crack path was nearly perpendicular to the loading direction for the cases of MD and TD, while inclined for the other angles. For modeIcrack propagation in MD, TD and resin, the crack propagation rate is expressed as a power function of a parameter corresponding to the crack-tip radius, H_IΔG_I, where H_I is a compliance parameter. The crack propagation rate under mixed mode I and II was correlated to the range of the total energy release rate, ΔG_<total> divied by Young's modulus.

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Fatigue limit and fracture patterns in epoxy based carbon composite were examined. When all fiber direction was along the specimen axis, higher value of fatigue limit was obtained. In this case, the stable crack growth tended to occur. When the directions of carbon fibers were parallel and perpendicular to the specimen axis, fatigue limit was lower. In this case, the unstable crack growth tended to occur. It is concluded that there is good relationship between fracture pattern and fatigue limit in the case of present study.

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This paper describes elasto-plastic damage model coupled combined hardening rule and damage based on Continuum Damage Mechanics. This model reproduce material damage in the elastic-plastic state and behavior of the stress and strain due to cyclic load. We conducted the fatigue test of S45C test piece and report the results were examined material damage and deformation behavior by very low cycle fatigue.

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In this study, the fatigue behavior of TiNi alloy under various hydrogen environments was investigated by using thin wires with the diameter of 0.7 mm. In particular, the effect of frequency in hydrogen environments was investigated. Fatigue tests with stress ratio of R=0.1 were conducted in four kinds of environments: NaOH solution with hydrogen charging (current density J=127 mA/mm^2 and 0.0254 mA/mm^2), NaOH solution without charging, and pure water. Fatigue life decreased in these all hydrogen environments than in air. The effect of hydrogen charging current density on fatigue life was very small. The effect of frequency in current density J=127 mA/mm^2 was similar to that in ordinary metal corrosion fatigue, while in current density J=0.0254 mA/mm^2, the frequency effect was very small in the range of stress amplitude above fatigue limit in air, and the fatigue life depended on number of cycles. Therefore, life prediction by net stress model was conducted for current density J=127 mA/mm^2. As a result, the predictions agreed with the test results.

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In order to achieve shear mode crack propagation that appears on the surface of rolling/sliding contact machine elements along with the plastic flow, a test method was developed. Rolling contact fatigue is the damage of rolling/sliding contact machine elements, and the crack exists along with the plastic flow. For the applied stress around the crack, shear stress is considered to be dominant caused by the rolling/sliding contact. And the authors considered that the plastic flow acts as a guide to Mode II crack propagation and prevents the branching. The depth of the plastic flow layer on the rolling/sliding contact machine element surface is a few hundred of microns. Therefore, in this study, in order to achieve Mode II fatigue crack growth test of such thin area, a test method was developed. After the cyclic loading, the Mode II crack propagation without compression load was succeeded. The authors concluded that crack growth direction was guided by plastic flow.

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The subloading crystal plasticity model is endowed with the distinguished advantages that the yield judgment is not required and possesses the automatic controlling function to attract the resolved shear stress to the critical shear stress in the plastic slip process. The subloading crystal plasticity model will be modified by incorporating the pertinent evolution rule for the kinematic hardening proposed by Hardero) and its application to the isotropic hardening in this article.

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Inelastic strain rate is induced only by the stress rate component normal to the yield surface in the traditional elastoplastic constitutive equation since it is given only by the plastic strain rate derived from the consistency condition for the yield surface. However, it would be induced also by the stress rate component tangential to the yield surface in real material behavior. The inelastic strain rate induced by the deviatoric stress rate component tangential to the subloading surface is formulated in this article.

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The texture evolutions of Ni alloys are evaluated using the crystal plasticity. We incorporate the twinning deformation in the crystal plasticity to simulate both the Cu type texture of rolled pure Ni and the Brass type texture of rolled Alloy C22. Calculation results of texture have the very similar characteristics in crystal orientation distribution to experimental results.

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The subloading surface model has been formulated and applied to the prediction of cyclic loading behavior of metals. This article presents a formulation of the stress-update algorithm for the extended subloading surface model. The stress-update algorithm by the return mapping using the fully implicit algorithm is formulated aiming at obtaining calculation results in high accuracy and efficiency. It is incorporated into the implicit finite element program Abaqus through the User-subroutine UMAT. We simulate elastoplastic behaviors of metal to assess calculation accuracy and efficiency of the proposed algorithm.

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A new material model based on non-associated flow rule for anisotropic metals has been proposed. To predict the fracture during metal forming, an appropriate material model should be applied. However, the conventional models have some difficulty for this purpose because they cannot separately evaluate the stress anisotropy and the deformation, plastic strain rate, anisotropy. A plastic strain rate tensor should be permitted to follow the rotation of the stress rate tensor, which rotates instantly from the direction of the current stress tensor as in the case of plastic instability. Therefore, a non-associated flow model, in which the plastic potential function is defined independently of the yield function, has been proposed. In this report, the outline of the proposed model is presented.

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Residual stress and deformation occur by the change of mechanical properties and volume caused by phase transformation during quenching. In the past, elasto-plastic analysis combined with phase transformation analysis method, in which volume fraction of 4 phases (Ferrite, Pearlite, Bainite and Martensite) during heat treatment process can be individually taken into account, was constructed for the prediction of residual stress caused by heat treatment such as induction hardening. In this paper, changes of stress and strain during tempering are taken into account and applied to the prediction of residual stress of S50C steel crankshaft to verify the validity of this method.

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Multiwalled carbon nanotubes (MWCNTs) in uncured ultraviolet ray curing resin thin suspension of several cm squares were aligned by applying the multi-phase voltage. After the alignment, the suspension was cured by irradiating ultraviolet ray. Then, electrical resistivities of the thin films in which the MWCNTs were loaded by 0-0.5 wt% were measured in parallel and vertical directions to the aligned MWCNTs direction. The multiple-electrode used to the experiment was constructed by 24 long and slender electrodes. The cover glass was put on the multiple-electrode, and the suspension was dropped on the cover glass and expanded by compression load. The multi-phase voltage was applied to the multiple-electrode, and the traveling electric field was applied to the suspension

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This paper studies the Mode I fracture behavior and crack monitoring of bonded carbon fiber reinforced polymer (CFRP) composite joints with carbon nanotube (CNT)-based polymer adhesive layer. Mode I fracture tests were carried out with double cantilever beam (DCB) bonded joint specimens consisting of woven carbon/epoxy composite adherends and CNT-based epoxy adhesives, and the critical energy release rate at the onset of crack growth, i.e., fracture toughness, was evaluated. The electrical resistance of the bonded joint specimens was also monitored during the tests. An analytical model based on the electrical conduction mechanism of CNT-based polymers was employed to describe the electrical resistance change due to crack propagation in the bonded joint specimens, and a good correlation was obtained between the predicted and measured results.

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