The authors applied MPI/OpenMP hybrid parallel programming model to molecular dynamics (MD) for simulating a protein structure. In a symmetric multiprocessor (SMP) cluster architecture, it can be expected that the hybrid parallel programming model, which uses the message passing library such as MPI for inter-SMP node communication and the loop directives such as OpenMP for intra-SMP node parallelization, is the most effective one. In this study, the parallel performance of the hybrid style was compared with that of conventional flat parallel programming style, which uses only MPI. The computer environments used here are Hitachi SR8000/MPP placed at the University of Tokyo. When using 16 SMP nodes (128 PEs), it was observed that the parallel efficiency with the hybrid style was 90%, which was 15% higher than that of the flat-MPI for MD simulation of a protein with 33 402 atoms.

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In the development of various advanced materials by controlling their heterogeneous microstructures, there is a growing need for the multi-scale analysis. There have been many studies on the correlation between the heterogeneous microstructure and the macroscopic properties mainly using the asymptotic homogenization method with the help of the finite element method. Although the consideration of fracture origin in components such as interface crack is important in the multi-scale stress analysis, it was impossible to calculate the microscopic stress under high gradient of macroscopic strain/stress field at the crack tip. Furthermore, the representative dimension of the fracture origin lies between the microscopic scale and the macroscopic one. Hence, this paper proposes a novel three-scale computational method that employs both the homogenization method and the enhanced mesh superposition method to study the correlation among microstructure, component and fracture origin simultaneously. An equation solver for large-scale 3 D analysis by the mesh superposition method is also presented. A demonstrative 3 D example of porous thin film with interface crack, whose finite element model has approximately 78 thousand solid elements, is shown.

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Resonant ultrasound spectroscopy (RUS) is widely used to evaluate the characteristics of small solid specimens like superconductor of a single crystal or anisotropic materials of fiber reinforced composites, for example. The elastic moduli of the solid body can be determined by measurement of the resonant frequencies exited by a pair of Piezo-electronic transducer. In this paper, a numerical technique for the determination of the elastic constants in RUS testing is discussed. An alternative evaluation function for the search algorithm of the elastic moduli is employed, and boundary element analysis is applied to compute the eigenvalue of the 3 dimensional vibration on the solid body. Furthermore, genetic algorithm is introduced to avoid some difficulties on the identification process for the anisotropic material. Some numerical simulations for the steel blocks, single crystal and CFRP laminate are conducted to demonstrate the effectiveness of the present method.

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In forging operations, an appropriate die-shape determination is of vital importance. This paper presents a new method for automatic determination of the intermediate die surface in multi-step forging based on an optimization technique. In the first stage of the process, using a unique design parameter which generates the shape lying between the pre-form and the final product, a preliminary die surface, which gives the lowest forging load within the design space, is determined. In the second stage, further detailed optimization by local search is performed around thus obtained solution at the first stage. Constraints for avoiding material defects such as folding and cracking during forging are considered. The validity of this method has been confirmed by applying it to the die design for an axisymmetric backward extrusion problem.

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This study is concerned with biomechanical evaluations of isthmic spondylolisthesis that causes slippage of a defected vertebra. Because the frequency of this disease depends on the site of spondylolysis, it is supposed that the mechanical boundary condition in lower lumbar spine has influence on isthmic spondylolisthesis. To clarify the mechanism of isthmic spondylolisthesis, the effects of isthmic defect on stress distribution in intervertebral disks were investigated by using a three-dimensional finite element model of a whole spine. The results of extension motion analyses show that the maximum compressive principal stress of L 4-L 5 disk in L 4 defect model is significantly increased in comparison with that of an intact model and the instability of the defect vertebra is also increased. Such a high compression on the disk may cause disk degeneration which leads to spondylolisthesis.

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Computer simulation has been conducted to investigate the cluster formation process through diffusion-limited aggregation. In the simulation, cluster growth was assumed to take place on three types of 2-dimensional lattice, namely, triangular, square and hexagonal. Influence of lattice types on cluster characteristics was studied among these three types of lattice, comparing indices such as cluster diameter, fractal dimension, density distribution along radius, average of contact number and contact location. Moreover, comparison was made between on-lattice and off-lattice cluster growth.

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This paper presents a method for the analysis of two-dimensional crack problems using the boundary element method. In the present method, a domain to be analyzed is divided into two regions : the near-tip region, which is circular in shape and centered at the crack tip, and the outer region. The displacements and stresses in the near-tip region are represented by the truncated infinite series of the eigenfunction with unknown coefficients. The stress intensity factor is represented by one of the coefficients. The outer region is formulated by the boundary element method. The system of linear algebraic equations with respect to nodal displacements, nodal tractions and the coefficients of the series are constructed by discretized boundary integration in the outer region and the continuity conditions. To test the accuracy of the present method the center slant cracked rectangular plate under a uniform tension has been analyzed. The isoparametric linear elements are used. The calculated dimensionless stress intensity factors are in good accuracy.

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In this paper the problem of an antiplane vertical crack in a coated strip of functionally graded piezoelectric material (FGPM) is studied. It is assumed that the elastic stiffness, piezoelectric constant, and dielectric permitivity of the FGPM vary continuously along the thickness of the strip. The coated strip is under anti-plane mechanical and in-plane electric loads. The solutions involve solving singular integral equations by application of the Gauss-Jacobi integration formula. Numerical calculations are carried out to obtain the stress/electric displacement intensity factors and the energy density factors. They are greatly affected by the geometric parameters, the FGPM graded properties and the electromechanical loading.

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The purpose of this work is to develop the procedure and mathematic model to estimate mechanical properties of short grass fiber filled PA6. First, vibration tests were carried out to study vibration characteristics of composite material. Then various micro-mechanics models for short fiber composites are evaluated using vibration and tensile test varying in-plane tensile angle. Along the evaluation, a combination of micro-mechanics model is proposed to get appropriate results. Also, procedure to identify young's modulus of matrix and dumping factor of composite by comparison of vibration test results and FEM considering in-plane distributions of fiber orientation is demonstrated. Through evaluation, the FEM analysis using mechanical properties of composite material determined by proposed procedures considering fiber orientation and distribution of fiber orientation angle gives good estimation

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The mode II fatigue crack growth behavior from delamination was investigated with UD laminates (made of unidirectional laminates) and C laminates (made of unidirectional laminates and cloth laminates) of high strength glass fiber reinforced plastics (GFRP). Fatigue crack growth tests were carried out by end notched flexure speciments at the stress ratios R=0.3, 0.1, -0.5, and -1.In UD laminates, the theshold of energy release rate range, ΔG_IIth, of fatigue crack growth was independent of the stress ratio. In C laminates, the ΔG_IIth value at negative stress ratios was about four times of that at positive stress ratios. In C laminates, a fatigue crack propagated along the interface of the unidirectional laminate at positive stress ratios, while along the interface of the cloth laminate at negative stress ratios. When the stress ratio was negative, the fracture surface of C laminates was rough because of the resin rich area of fabric crossing, and this roughness shielded the crack tip, restricting the shearing deformation near the crack tip. Thus the crack growth resistance of C laminates at negative stress ratios in much larger than that at positive stress ratios.

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A small in-plane bending fatigue testing machine forin-situ observation of small fatigue crack growth behavior by means of an atomic force microscope (AFM) was successfully developed. Laminated piezoelectric ceramics were adopted as an actuator in order to miniaturize the fatigue loading facility operating on the stage of an AFM. Small fatigue crack growth test under constant amplitude loading was then carried out on α-brass and successive observation of small fatigue crack growth behavior was performed by the AFM. The fatigue crack tended to grow along one slip direction with the highest Schmid factor, as the crack driving force of a small crack was not large enough to operate other slip directions with lower Schmid factors simultaneously. Frequent crack branching and kinking behavior were also observed during crack growth. It was considered that the constraint of slip deformation due to the cyclic strain hardening was mainly responsible for crack branching and kinking behavior. The intervals of branching or kinking were affected by the difference of mobility among slip planes.

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Mode I stress intensity factors for part-through crack were evaluated from the crack opening displacement distributions measured along the crack on the surface in a finite plate. This method was originally proposed for a through crack in a finite plate using complex valued-formulae of a crack in an infinite plate and was extended to a part-through crack in a finite plate. For the analytical results using FEM analyses, the stress intensity factor K_est-values obtained by this method showed close agreement with stress intensity factors calculated from Newman-Raju's equation. Furthermore, for the experimental results using annealed cracks without residual stresses, the evaluated K_est-values were in good agreement with the stress intensity factors calculated from Newman-Raju's equation. This method was also useful to evaluate the fatigue crack propagation rate of part-through cracks with the compressive residual stress in the wake of the propagating fatigue cracks, even though applied stresses and residual stress distributions are unknown in materials.

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In this paper, we consider the decrease in threshold stress intensity factor (SIF) range ΔK_th due to high maximum SIF K_max, that is observed for several materials in the tests by K_max constant method when i) closure-free and ii) non-corrosive atmosphere conditions are realized. We proposed an assessment criterion to predict this phenomenon from the past data for Al and Ti and showed that the criterion is valid also for steels. Finally we proposed a simplified model to explain the phenomenon, considering the fact that marks of static fracture are observed on the fracture surface.

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In this paper, push-pull fatigue tests of notched specimens under R =-1, 0 and 0.5 were carried out on annealed 0.1% carbon steel with the Vickers hardness H_v=105 and quenched-tempered 0.5% carbon steel with H_v=582. The fatigue limit of a long crack, σ_w2, was obtained from that of a notched specimen with a sharp and deep notch whose radius is smaller than the branch point ρo. Using the present and past σ_w2 data, the effect of the positive mean stress on the ΔK_w of the long crack was evaluated by using 3.2HB (≅σ_B) and σs/ (3.2H_B), where ΔK_w is the stress intensity factor range for the purpose of predicting the fatigue limit of a metal with an arbitrary crack, σ_s is the lower yield stress or 0.2% proof stress, σB is the ultimate tensile strength and H_B is the Brinell hardness. Although the σ_w2 decreased with the mean stress, σ_w2 was cut off by the threshold stress σ_w2 of the plastic deformation at crack tip. For the quantitative prediction of the fatigue limit of a cracked steel with an arbitrary crack length under a positive mean stress, he σ_w2 and σ_w2 values were approximated with simple formulae.

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The fracture experiment of a crack in a weld line between two different steels (SPC and HT 60) was carried out over the temperature range from -196°C to room temperature. Different from a crack in a material, the fracture mode change from mode I (opening) type to mode II (in-plane shearing) type due to the difference of material properties of two steels was observed with the increase of temperature in addition to brittle-ductile transition behavior. That is, in the range below -150°C, only mode I brittle fracture occurred without blunting of a crack tip. In the range from -150°C to -100°C, although a crack tip a little blunted, unstable mode I brittle fracture occurred. In the range from -100°C to -75°C, a crack showed stable mode II ductile fracture first, then, changed to unstable mode I brittle fracture, and, in the range from -75°C to room temperature, a crack showed stable mode II ductile fracture first, then, changed to stable mode I ductile fracture. The CED (crack energy density) in an arbitrary direction were evaluated through the results of finite element analyses corresponding to the fracture experiment. It was shown that a dramatic increase of fracture resistance by brittle-ductile transition cannot be expected for a crack in a weld line between two different steels because brittle-ductile transition is accompanied by fracture mode change from mode I to mode II.

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The small punch (SP) tests were conducted at 77 K and 4 K using austenitic stainless steels JN 1, JJ 1 and JK 2, which have been recently developed for use as a cryogenic structural material. The tests were applied to the steels aged at 923-1073 K to investigate changes in their toughness at cryogenic temperature due to thermal aging. The area under the load-deflection curve up to the macro-crack initiation was defined as SP energy to evaluate the fracture toughness of the steels. The experimental results showed that the SP energy of JN 1 decreased monotonously with an increase in aging temperature. On the other hand, the SP energy of JK 2 showed no significant change even after the thermal aging at 923 K and 973 K and decreased after the thermal aging at 1023 K. Metallographic examination revealed that this difference in decrease of SP energy due to thermal aging was caused by the variation in amount and distribution of grain boundary M23C6 carbides. As a consequence, JN 1 was more susceptible to thermal aging embrittlement than the other steels, and high resistance of JK 2 to embrittlement was attributable to the depression of precipitation and coarsening of grain boundary precipitates.

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Residual stress, hardness, toughness and adhesive strength of TiN coatings deposited on carbon steel S45C by DC magnetron sputtering under three sputtering gas pressures 0.5 Pa, 0.8 Pa and 1.76 Pa were investigated. The residual stress once increased and then dehreased with increasing bias voltage at 0.5 Pa and 0.8 Pa, but increased monotonously at 1.76 Pa. Comparing at relatively low bias voltage, it increased with decreasing gas pressure. These residual stresses were considered to be generated by bombardment with high-energy ions during the coating process, and these variations could be explained by the difference of bombarding energy at each gas pressure. The variations of hardness and toughness with increasing bias voltage at each gas pressure correlated with the variation in residual stress at corresponding gas pressure. Increasing bias voltage, the adhesive strength decreased at 1.76 Pa, increased at 0.5 Pa, once decreased and then increased at 0.8 Pa. The qualitative tendency of its variation also could be explained by the difference of bomgarding energy at each gas pressure.

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Recently, the high-speed submerged water-jet peening using the high impact pressures being accompanied by the bubble collapse is attracting attention. In this study, therefore, in order to improve such a peening effect and to make rapid progress of the applicable range, we take up a typical water-jet accompanied by uniformly large bubble-cloud, the time dependent change of residual stress is systematically measured on the gear surface by means of the X-ray diffraction method for a complex mechanical part of complicated shape (single helical gear of SCr420H3V2L2 carbon steel), and the definite peening effectiveness has been verified. We show on the surface that the residual tensile stress can be effectively improved into the residual compressive stress. It is also confirmed that uniform peening effect well works even for such very complex parts.

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Since stress peening can obtain a larger compressive residual stress compared with non-stress shot peening, it has a large effect on improving fatigue strength and it is used in leaf spring. However, when remaking to the stress peening, no systematical study can be seen. It can be said that it is not clear about the mechanism. So it carried out stress shot peening's experiment about bending, simple tension and torsion by using plate specimen and round bar. It was made clear about whether what percent of loaded pre-stress was added to the residual stress, and effect of specimen's size existed. When pre-stress was removed, what percent of loaded pre-stress is added to compressive residual stress. This rate is called effect of pre-stress. Simple tension had the largest effect of pre-stress, and bending and torsion became the same result. It could be seen that effect of pre-stress tended to increase in proportion with increasing specimen's size, and after that became the saturation.

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Nowadays roll core sandwich panels (RSPs) have been widely used in various structures, and thus, to identify the bending properties of RSPs is significant. The present paper aims to investigate the bending properties of RSPs by three-point bending tests. The study clarified the effects of core height, direction of roll core, and the position of applied load on the bending properties. The study also found that the RSPs were more useful for mobile and other types of structures, compared with the conventional honeycomb sandwich panels (HSPs) that are widely used now. Futhermore, theoretical shear moduli were obtained with Gibson's method, taking into account the anisotropy. The estimated displacements where the theoretical shear moduli were used coincided well with the results of the bending test for each direction.

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Various products which used a magnet have been developed, and it is necessary to learn about its practical use in Industry Arts Course at Junior High School. Then, three kinds of teaching tool for learning the mechanism of an eddy current experinentally were developed as an example of practical use of magnet. Developed teaching tools as follows ; (1) it is a slide teaching tool that a magnet slip down on the slope made of various metals, (2) it is a coin falling teaching tool that various coins slip down on the slope in which two magnets are set in parellel on the way, (3) it is a torque measurement teaching tool that the rotating speed of aluminum disk is deduced by applying the magnetic field, and its torque is measured. As these results, the work of an eddy current could be learned in experience and the concern about magnet or science of students was able to be raised.

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