It was found in a recent experiment done by J. Zhang and co-workers that a flexible filament in a flowing soap film can exhibit three states-the stretched-straight state, the flapping state, and the bistability. When this experimental model is regarded as a one-dimensional flag in a two-dimensional fluid flow, their findings contradict the common idea that flags always flap in a wind. In this paper, the flag-in-wind problem is simulated by a fluid-structure interaction finite element analysis, where the Navier-Stokes equations based on the ALE method is strongly coupled with the Lagrangian equilibrium equations of the structure. In the simulation the three states are successfully reproduced, and the effects of some representative parameters on the amplitude and frequency of the oscillation are investigated to reveal the underlying mechanism of the flag flapping.

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A technique for automatically generating a hexahedral mesh of a complex solid model was developed. This technique can automate the interactive operations (such as model editing) that are carried out as a pretreatment for hexahedral-mesh generation. Consequently, the time taken by these interactive operations was significantly shortened, and high-speed generation of a hexahedral mesh was thus possible. Furthermore, the developed technique was applied to the generation of a hexahedral mesh of an engine-block model. And it was confirmed that the mesh generation time is shortened to one tenth of that for the conventional method.

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This study provides dynamic analysis of solids by MPS (Moving Particle Semi-implicit) method. A two-dimensional code based on particle interaction model of MPS method is developed to simulate elastic behaviors, large deformation and fracture in solids. Meshes are not needed in the MPS method, so that fracture as well as large deformation can be analyzed without mesh distortion. We propose a new particle method for dynamic simulation of elasticity. The equation of motion in elastic solids that is characterized by material density, Young's modulus and Poisson's ratio is discretized to particle interaction between neighboring particles. Rotation of particles is considered for the conservation of angular momentum in the discretized formulation. We had good results about not only conservation of momentum in physical quantities but also reciprocal action of displacements and stress distributions in elastic models. Limit of numerical stability is obtained. Large deformation and fracture of various solids are simulated. The results show good agreement with experiments.

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Interface energy and stress at amorphous-crystal interface are important quantities which reflect the microstructure of polycrytalline thin films. In this paper, we study well-relaxed amorphous-crystal interface with molecular dynamics simulation and propose a new method to provide these quantities by using several order-parameters to evaluate atomistic microstructure. We obtain values of the interface energy, 0.29±0.08J/m² and 0.33±0.08J/m² for (100) and (111) plane, respectively, which are good agreement with experimental data. We also find that these interface properties are strongly influenced by structural relaxation. We show that the dependence of the interface energy on the crystal orientation is small, and that the interface stress involves the scattering across a broad range. Critical nucleus size estimated from the interface energy is slightly smaller than that estimated by direct molecular dynamics simulation for homogeneous nucleation. This disagreement is thought to be attributed to the continuum approximation of the classical nucleation theory applied to the small cluster.

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In this paper, the large deflection problem of a circular plate subjected to internal pressure is treated. In-plane tension is acting before subjecting the pressure loading. In the deformation analysis of the circular plate, simultaneous nonlinear differential equation system is derived by applying the von Kárrmán's large deflection theory. The circular plate is clamped or simply supported at the boundary edge. At the finite element method formulation, the Galerkin method that is a kind of weighted residual method is applied. By numerical calculation, the present solution is compared with the solutions obtained from linear theory and the Heckey's membrane theory. Furthermore, it is also shown that the present solution approaches to the membrane solution for large values of a pressure parameter.

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High polymer materials are remarkably weak to heat compared with the metal and ceramics. And, there is a limit in the use of high polymer materials as parts of the structure. Therefore, to expand the range of use of high polymer materials further, the strength evaluation by the high temperature environment is needed. In this study, the polycarbonate was examined as a sample material about static and dynamic fracture behaviors in the high temperature environment. The stress intensity factor was determined by using method of caustics. An environmental temperatures ware assumed to be a room temperature, 40, 60, 80, and 100°C. The crack model assumed V-notch, and aimed at the union of the specimen configurations. As a result, the stress intensity factor indicated a small value by the temperature high. The same the vibration behavior of the dynamic stress intensity factor by which the temperature change is accompanied has been understood. As for static and dynamic fracture toughness values, the tendency which decreased gradually along with the rise of the temperature was obtained. It has been understood that the difference of dry processing of the specimen greatly exerts the influence from static by the dynamic fracture behavior.

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The design variable progressive optimization method, a kind of multilevel optimization based on RSA, was applied to optimize the shape of two-piece resealable aluminum beverage bottle bottoms. On the basis of sensitivity analyses, the most effective dimensions are selected as design variables in the first stage of design optimization, while the dimensions with relatively small influences are optimized in the secondary stage. In the design optimization of the bottom, the column strengh was maximized, the bulge strength was restricted to fall into a range, and the maximum bottom growth and the axial displacement of sidewall were constrained.

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The size effects on yield stress and hardening evolution in the crystal plastic deformation processes has been recognized through experimental observations. The quasi-simple shear experiments to evaluate the initial yield stress and the hardening evolution by employing different sizes of square plane specimen was executed. Consequently, the following results were obtained. As a first experimental result, the resolved shear stress depends on the initial mean free pass length of dislocations. As a second one, the process, in which dislocations reach and pass through the surface of a specimen, decreases the hardening evolution. As a third one, it was confirmed that the smaller the specimen, the higher hardening evolution because of accumulation of dislocation. Further, it was concluded that initial mean free pass length and geometrically necessary dislocation effect on hardening evolution should be introduced in the crystalline plastic constitutive equation.

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A modified non-schmid crystal plasticity based constitutive equation, considering the size effects on yield stress and hardening evolution, was proposed and implemented in an elastic crystal plastic finite element analysis code. The quasi-simple shear FE analyses and experiments by employing different size were executed to demonstrate size effects on stress-strain curves and strain distributions. An experiment based dislocation free pass length was introduced in the hardening evolution equation. FE analyses results of plastic deformation behavior have shown good agreement with experimental ones. Finally, the availability of this constitutive equation was confirmed.

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PZT piezoelectric thin films are promising candidates for use as microactuators or microsensors in MEMS (Micro Electro Mechanical Systems) or NEMS (Nano Electro Mechanical Systems) because of their quick response to electrical stimuli. In this research, the RF magnetron sputtering method is used to deposit PZT thin films. Sputtering conditions are proposed that control the crystalline plane (111) of perovskite structure for PZT in order to influence the piezoelectric constant. The substrate angle and temperature, Ar/O₂ pressure and flow rate were investigated by the heuristic and experimental design methods to optimize the PZT perovskite crystal thin film. The substrate temperature was the most important factor that affected the piezoelectric constant. The crystalline structure, surface topography and piezoelectric constant of the deposited PZT were observed by X-ray diffraction structural analysis, atomic force microscope and piezoelectric constant evaluation equipment. PZT thin films with only perovskite structure were obtained and PZT (110) was mostly dominated. With increased substrate temperature, PZT (111) was grown, and the piezoelectric property improved. The measured elastic modulus of 70 GPa for the deposited PZT was in good agreement with the quoted value for commercial based bulk PZT. We obtained a pizoelectric constant of d₃₁=-28 pm/V, and produced a high performance bimorph actuator.

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In this paper, a new head injury criterion evaluated by the hydrostatic stress occurred in the head crash phenomenon. In order to obtain the threshold value for brain's organ and tissue, in vitro impact experiments to cultured nerve cells were performed. PC-12 cultured nerve cell was employed to imitate the human's nerve cell. In the experiments, various pressure waves were generated by introducing different heights of dropping weight for impacting. Relationships between peak values of impact compressive and expansive pressure waves and detachment rates and injury rates evaluated by the cell membranes damage were obtained.

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The protection of spacecraft against hypervelocity impacts of space debris causing fatal damage to spacecraft stractures has received wide attention. In this paper is concerned with the numerical analysis of hypervelocity solid-solid impacts and evaluation of protection capability of double bumper debris shields. To analyze numerically the hypervelocity solid-solid impact phenomena, an improved Smoothed Particle Hydrodynamics (SPH) method with new particle generation and particle merger techniques is used. We first propose to evaluate the protection capability of debris shields on the basis of the kinetic energy of debris cloud through unit area at the position of pressure wall, and then evaluate the protection capability of double bumper debris shields. As a consequence, it is elucidated that the double bumper debris shields have high protection capability and could reduce the damage of pressure walls.

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A woodpecker strikes its beak toward a tree repeatedly. But, the damage of brain or the brain concussion doesn't occur by this action. Human cannot strike strongly the head without the damage of a brain. Therefore, It is predicted that the brain of a woodpecker is protected from the shock by some methods and that the woodpecker has the original mechanism to absorb a shock. In this study, the endoskeltal structure, especially head part structure of woodpecker is dissected and the impact-proof system is analyzed by FEM and model experiment. From the results, it is obvious that the woodpecker has the original impact-proof system as the unique states of hyoid bone, skull, tissue and brain. Moreover it is considered that woodpecker has the advanced impact-proof system relating with not only the head part but also with the whole body.

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Carbon tool steel substrates were quenched after TiN coating by dc magnetron sputtering, and the effect of the substrate post quenching on the mechanical properties of TiN films were investigated. The residual stress of TiN film decreased by the substrate post quenching. Corresponding to this, the hardness of TiN film also decreased. On the other hand, the adhesive strength obtained by the scratch test and the substrate hardness were improved by the substrate post quenching. The reason why the adhesive strength was improved was explained by the following three effects of the substrate post quenching ; the decrease of the residual stress, the increase of the substrate hardness, and the formation of the mixing layer between the film and the substrate caused by elevated temperature in the post quenching procedure.

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A method of improving mechanical properties of Al thin films by low energy ion irradiation treatment after the deposition was proposed in this study. The surface of the Al thin films deposited on the glass substrate was irradiated with low energy Ar ions for 30 minutes, ion acceleration voltage 50 V and 100 V, ion current density was changed from 0.15 to 0.4 mA/cm². Young modulus and hardness of Al thin film were increased, spacing of lattice planes d was decreased and peak intensity of Al (111) was increased after the irradiation. It is found that the improvement of mechanical properties of the Al films and increasing of peak intensity of Al (111) is related. Moreover it turns out that the irradiation effect of the ion acceleration voltage 50 V compared with 100 V is more remarkable. The proposed treatment method is expected to improve surface mechanical properties of metal thin films deposited by various formation techniques.

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This paper considered three dimensional internal inclined crack growth behaviors due to repeated rolling thermoelastic contact. In this analysis, crack is modeled as an internal inclined planar crack in a three dimensional half-space. Rolling contact is simulated as a long and narrow distributed load with both normal and shear components moving with constant velocity. At first, stress intensity factors along the crack contour are analyzed using high carbon chromium bearing steels. Next, numerical results of crack growth contours are given based on a modified Paris power low. And fatigue life is estimated by maximum crack growth. The shapes of crack contour and fatigue life are calculated under various conditions, which change sliding ratio, frictional coefficient, depth and angle of inclined crack. And influences of conditions, which affect the shapes and fatigue life, are considered from viewpoint of stress distributions in the state where there is no crack.

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Ductile cast iron is often used for automobile parts as having cast surfaces with shot blast. Influences of surface roughness, microstructure transition layers, a lot of kinds of defects and residual stresses on fatigue strength are very complicated. The microstructure in the cast transition layer contains a work hardening layer due to shot blast and a pearlitic layer or a ferritic layer produced by casting. To clarify the effect of surface roughness, microstructure transition layers and defects on fatigue strength, tension-compression fatigue tests have been carried out on the specimens composed of a ferrite-pearlitic structure. The residual stresses were relieved by annealing to evaluate various factors independently. The fatigue strength has been evaluated using the √area parameter model. The effective defect size √area_eff with the interaction between surface roughness and defects has been defined so as to evaluate the effect of surface roughness on fatigue strength. The evaluation of the maximum defect size by statistics of extreme and the lower bound of the scatter of fatigue strength have been proposed for practical design.

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This paper deals with fracture process of a ceramic/metal functionally graded material (FGM) under three-point bending. The used material has a functionally graded surface layer (FGM layer) on a stainless steel (SUS 304) substrate, and the FGM layer consists of partially stabilized zirconia (PSZ) and SUS 304. In order to investigate the fracture process of the FGM, three-point bending tests of rectangular specimens and numerical analyses are carried out. On the three-point bending tests, crack initiation and unstable crack growth occur on the FGM layer, and the crack is arrested at the interface between the FGM layer and substrate. Then, the crack branches and both crack-tips grow stably along the interface with increasing deformation. After a some amount of crack growth, the both crack-tips are arrested, and a new crack is initiated and grow into the SUS 304 substrate ahead of the initial cracking of the FGM layer. The finite element analyses taking account of distribution of a PSZ volume fraction and plasticity of SUS 304 phase are carried out for each stage of fracture process. Based on the numerical results of the stress intensity factors and stress distributions, the fracture behavior of the FGM is discussed in details.

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In order to examine the relationship between particle size and the strength of dental porcelains, the particle distributions of dental porcelains were measured using a laser diffraction particle distribution analyzer. Statistical analysis revealed that the particle distribution was well fitted to a three-parameter Weibull distribution. The bending strength of the glazed specimen was equal to or greater than that of the as-received specimen. This is thought to have resulted from the glass constituent of the porcelain undergoing fusion and flowing into the indentation cracks, thereby contributing to a recovery of bending strength. Using the author's process zone size fracture criterion, experimental data concerning the dependence of the bending strength of glazed specimens on cracking was clarified. The distribution of fracture toughness of glazed specimens agreed well with a two-parameter Weibull distribution. Analysis of the dependence of the bending strength of the glazed specimen on cross head speed indicated that the static fatigue sensitivity of the healed crack was not high.

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A partial differential equation is derived for the macroscopic total strain of a material containing mutual perpendicular slit-like cracks with respect to the crack densities of the cracks by using the incremental form of the Mori-Tanaka theorem. By solving the partial differential equation, the macroscopic total strain, the average interaction stress and hence the macroscopic elastic moduli are formulated as a function of the crack densities of the cracks. On the contrary to the results obtained by the ordinary Mori-Tanaka theorem, the resulting macroscopic elastic moduli asymptotically tend to zero as the crack densities of the cracks increse. The present results are in good agreement with the analytical results by means of the differential scheme and the numerical results given by Huang et al. [Int. J. Solids Struct., 33 (1996), 1575-1586] especially at relatively low crack density when the magnitudes of the crack densities of the mutual perpendicular slit-like cracks are equal to each other.

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For a unidirectional fiber-reinforced composite material containing matrix cracks, the differential equation for the macroscopic total strain of the material is derived with respect to the crack density by adding only a small amount of cracks into the matrix and by adopting the incremental form of the Mori-Tanaka theorem to the resultant model of the material. By solving the differential equation, the macroscopic elastic moduli are formulated as a function of crack density. By comparing the resulting macroscopic elastic moduli with those obtained by Taya's method, the range of crack density in which Taya's method is applicable is clarified. This range becomes wider when the volume fraction and the aspect ratio of fibers increase.

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The equivalent eigenstrain is difficult to determine for a incompressible reinforcement in a composite material since its bulk modulus becomes infinite in the equivalent expression to the hydrostatic component of stress. Same difficulty may occur for the case of an incompressible matrix. In the present study, the methods to determine the hydrostatic component of the equivalent eigenstrain are examined for these two cases. For the incompressible reinforcement, the physical condition that the volumetric strain in the reinforcement is zero in value is used instead of the equivalent expression in order to determine the hydrostatic equivalent eigenstrain. For the incompressible matrix, the Eshelby tensors are rearranged with respect to the Poisson's ratio of the matrix and these are substituting into the equivalent expression. As a result, the bulk modulus of the matrix in the equivalent expression is canceled by these Eshelby tensors and the equivalent eigenstrain can be determined successfully. Moreover, both techniques are used for the case that all constituents are incompressible. The resultant hydrostatic component of the equivalent eigenstrain becomes zero.

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Cemented carbide alloy is widely used for high strength and hardness. The tips of cemented carbide alloy are sintered from the WC powder and often brazed on the wide sliding surface. Although welding is better than brazing, the welding crack occurs sometimes because the cemented carbide alloy has low contents of the bonding metal. Functionally gradient composite material will be expected to improve the weldability. One of the factors of the crack is the residual stress existed in the material. This paper describes an X-ray measurement method of both residual stress in WC and Ni phase of the cemented carbide alloy. Six kinds of specimen with bonding material Ni from 10% to 60% weight contents were made by spark plasma sintering (SPS) system. The stresses of the specimen were measured by X-ray diffractometer. As a result, the average residual stress between WC and Ni phase was approximately 500 MPa in compression, while the stress was released considerably after annealing.

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This paper describes an application of friction stir welding (FSW) to manufacture railway car body made of aluminium hollow extrusions (double-skinned car body). In this paper, from the viewpoint of strength, we show our approach from a design of the joint's sectional shape to the final evaluation test using actual double-skinned car body joined by FSW. As far as design of the joint, reaction force in the workpiece coincident with heat input was considered. At load test, we evaluated stress levels at the joint, accuracy of the simulation of the car body and double-skinned car body's characteristics. As a result, railway car body joined by FSW can meet all the requirements for actual application.

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Solder joints between a package and a printed wiring board (PWB) of a portable electronic device sustain thermal cycling as a result of power on-off, cyclic bending by key pad operation, and impact bending by dropping. Therefore, the authors conducted heat cycling, cyclic bending, and cyclic impact bending tests on the ball grid array solder joints between a chip scale package and a PWB. The evaluated solders were Sn-3 Ag-0.5 Cu and Sn-37 Pb. The tests showed that the life cycles of the Sn-3 Ag-0.5 Cu solder joints for the feat cycling and cyclic bending tests were approximately twice those of the Sn-37 Pb solder joints. On the other hand, in the case of cyclic impact bending test, the life cycle of the Sn-3 Ag-0.5 Cu joint under large strain was smaller than that of the Sn-37 Pb solder joint because of interfacial crack growth between the solder and the PWB. These fatigue lives of the joints were compared with crack initiation and failure lives of plain specimens by calculating local strain ranges in the joints by elastic plastic finite element analysis.

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