In this paper, formulations for homogenization method using the boundary element method (BEM) for unit cell analysis are presented. Unlike the finite element method (FEM), the application of BEM for the homogenization analyses is not fully explored. Possible formulations, a full knowledge of numerical implementation and appropriate expressions for the effective elastic moduli, when BEM is employed in unit cell analysis, are not fully explored yet. The purpose of present paper is to discuss possible equation formulations, numerical implementations and formulations for the effective elastic moduli, which are suited for BEM unit cell analysis. Two different BEM formulations for unit cell analysis (multi-region and single-region with volume integral) are presented. Periodic boundary conditions and numerical procedures are discussed, and then formulas for effective elastic moduli are presented. Finally some numerical examples are presented.

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In this paper, a finite element analysis of laminated composite plates with piezoelectric laminae is developed. This formulation is based on the first-order shear deformation theory. This theory is extended to include the piezothermoelastic response of composite plate structures. The element employed is a triangle with 18 degree-of-freedom which include extension, bending and transverse shear deformation states. Numerical results show that moderately thick piezothermoelastic composites are sensitive to shear deformation.

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The dynamic responses of two-dimensional granular material subjected to the oblique impact and side impact of a spherical projectile are investigated experimentally and also numerically by using discrete element method. The granular material is modeled by the 329 nylon spheres arranged regularly and two-dimensionally in a rectangular container. The numerical simulations are carried out at the impact velocities less than 10 m/s. The numerical simulations are compared with the results of measurements using high-speed video camera. It is ascertained that the motion of each particle can be well simulated by discrete element method. The dynamic response of the particulate aggregation is elucidated by probing the distribution of velocity vectors of individual particle and normal direction component of contact forces between particles in detail. The effect of wave propagation on the shattering behavior of granular materials is manifested. It is found that the dynamic arching in granular material is formed just under impact point.

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Fracture of machines and structures in general is caused by the existence of stress concentration. Therefore, it is important to know the values of stress concentration factor K_t or stress intensity factor K_I, K_II. In many cases, those values can be obtained from stress concentration handbooks. However, the values given in a handbook is not necessarily accurate. So, in this paper, the accuracy of the values of K_I and K_II given in a handbook are examined through the exact values calculated by the versatile program for two-dimensional stress analyses based on the body force method.

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Coalescence process of metallic atom clusters is studied by newly devised multi-resolution molecular dynamics (MRMD) method which combines ordinary molecular dynamics (MD) method with rigid body dynamics. Based on the concept that molecular or atomic motion is important and effective only in a surface region in which clusters are contacting, a set of equations of motion are derived from a single Lagrangian composed of whole variables in atomic system by using assumptions of rigid body motion according to accuracy required in each region. In simulation of two equivalent clusters' collision, comparison of MRMD results with ordinary MD results is made in respect to trajectories of cluster center, energies, and angular momentums. It is found that these methods produce coincident shapes and motions of cluster. Increase of kinetic energy obtained by using MRMD method when clusters coalesce, however, is smaller than that obtained by using ordinary MD method. It is also found that proper transmission of rotational motion in clusters' system can be possible by adopting a conservation scheme of angular momentum in rigid body dynamics. As a result, contraction of calculation time is realized by the MRMD method.

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Axial crush behavior of strengthening structural members is numerically simulated by the use of the dynamic explicit FEM code DYNA3D. The numerical model of the structure is composed of the shell elements and the material is assumed as a mild steel or a high tensile strength steel corresponding to the performed experiment. A drop hammer composed of solid finite-elements hits the top edge of the structure at 10 m/s, keeping its lower edge embedded into the rigid base. The calculated hat-shaped cross-sections are three types of rectangles and a more complex shape with a rectangular concave portion on the hat top. The axial length of the strticture is 120∼200 mm. When the accordion type cyclic buckling mode takes place, the crush strength is high and thus the structure attains a high capacity of the energy absorption. Another mode of bending collapse around a single plastic hinge also occurs under some conditions. In this case, the structure has a low capacity of energy absorption and thus is not preferable. The calculated crush strength agrees well with the corresponding experimental result, especially for the high strength material. The crush strength is larger for the shorter hat-height, which is coincident with the experimental result. It is also well simulated numerically that a more complex shape of the cross-section leads a higher crush strength.

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It is desired to develop the identification scheme of the principal axis of plastic anisotrypy of polycrystalline sheet metal to the improvement of calculation accuracy of formability. Elastic anisotropy is due to texture, it is same cause with plastic anisotropy, therefore, plastic anisotropy can be measured through phase velocity measurement of an ultrasonic wave. The rotation of the principal axis and the change of elastic constants of a sheet metal for press forming during plastic deformation are identified with the phase velocity of Rayleigh wave. It is demonstrated that the principal axis rotates independently of the material fiber.

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This paper describes an analytical formulation and a numerical solution of the dynamic problems of multi-layered porous shells of revolution saturated in viscous fluid. Each layer has different porosity and void diameter. The equations of motion and the relations between the strains and displacements are derived by extending the Sanders elastic shell theory. As the constitutive relations, the consolidation theory of Biot for models of fluid-solid mixtures is employed. The flow of viscous fluid through a porous elastic solid is governed by Darcy's law. On the boundary surface of each layer, it is assumed that there is no flow resistance and the fluid pressure and the fluid flow are continuous. The fluid flow equations and deformation equations of shells are numerically solved using the finite difference method. As a numerical example, the simply supported three-layered truncated conical shell under a semi-sinusoidal internal load with respect to time is analyzed. Numerical computations are carried out by changing porosity and mean void diameter of each layer, and the variations of pore pressure, displacements and internal forces with time are discussed.

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This paper describes the application of neural network for nano-indentation testing to evaluate mechanical properties of multi-layered thin films. The properties of films are evaluated from a set of load-depth curves which is obtained by indentation using spherical indenters having different radii. In this study, finite element simulation of indentation is conducted to provide learning data of the network. Two multi-layered networks are independently used to identify the properties of films. By using the first network, the ranges of estimation are roughly estimated, and the appropriate properties can be determined by the second network. It is demonstrated that Young's moduli of 4-layered films can be successfully determined by the proposed method. It is also shown that both of Young's modulus and thickness can be identified 2-layered films.

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In the previous study, micromechanical modeling of an intelligent material containing shape-memory polymer particles was performed by taking into consideration of distributions of glass-transition temperature T_g of particles. The macroscopic elastic modulus of the material E could be formulated successfully as a function of the differences of shear modulus and bulk modulus between particle and matrix, and the numerical results of E were reasonable irrespective of T_g distributions of particles. In this study, by considering not only T_g distribution of particles but also pre-strain which is given to a particle a priori and corresponds to the shape recovery strain of the particle, micromechanical analysis of same intelligent material as before is performed on the macroscopic elastic modulus. In modeling, thermal expansion strain due to mismatch between coefficients of thermal expansion of a particle and a matrix is also considered. By analyzing the model, the macroscopic elastic modulus can be expressed in terms of the shape recovery strain of particles and thermal expansion strain in addition to T_g distribution function.

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In the previous study, micromechanical analysis of stiffness of an intelligent material containing shape memory polymer particles was performed by taking into consideration of the distributions of glass-transition temperature T_g of the particle and the magnitude of pre-strain given to a particle a priori. In this study, by using the previous results, temperature dependence of the macroscopic elastic modulus E of such a material is calculated to the given T_g distributions. It can be seen from the results that the value of E after shape recovery of particles increases with increasing the prestrain and such increase in E is strongly influenced by T_g distribution of particles and the maximum heating temperature of the material. We conclude from these results that the macroscopic stiffness of an intelligent material containing shape memory polymer particles may be designed after shape recovery of particles by the proper choice of the type of T_g distribution of particles.

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In the current manufacture of multi-layer printed wiring boards, the method frequently used to laminate the core with insulating resin as build-up layer. However, a problem has emerged in that the strength of the substrate decreases due to the insulating resin part as the multi-layers are progressively formed. Thus, it becomes necessary to use FRP for the insulation layer part. Especially among various kinds of FRPs, AFRP has been considered a suitable FRP because of its low coefficient of linear thermal expansion in the x-y plane. On the other hand, there are various kinds of aramid fibers used to reinforce the plastics. Kevlar fiber and Thecnora fiber are well known among them. Therefore, this paper describes the small diameter drilling in the printed wiring board made of Kevlar fiber reinforced plastics and Thecnora fiber reinforced ones. Especially this report dealt with the blind via holes formed by CO₂ laser and the through hole drilled by a conventional drill tools. The machinability of two types AFRP was compared in small diameter drilling for circuit connection.

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The inner microstructure of blend specimen with the 20% addition of LCP was investigated in this paper, especially in discussion the effect of the stress amplitude on the fatigue fracture property and the effect of LCP addition. The results are following as: (1) PP/LCP blend is an immiscible two-phase material. The diameter of LCP fiber phase would become large from middle layer to core. (2) Companion to add LCP, (a) E' increased and tan δ was low, it showed that the strength increased and the ability of the inner heating itself decreased. (b) The tensile strength increased, but the stretch largely decreased. (c) The microhardness distribution on the specimen surface was improved and the stress concentration on the middle layer would be relaxed. Thus, the fatigue fracture changed to the trend of the brittle damage and the lifetime became long. (3) The severity of the specimen heating itself resulted in the increase in the stress amplitude, the low E' and high tan δ would obviously show. The reinforcement LCP would soften and pulled out from PP matrix. The fracture trend of specimen would change from brittle to ductile.

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Fatigue properties of tungsten fiber reinforced Ti-6Al-4V (W/Ti-6Al-4V) alloy has been investigated. W/Ti-6Al-4V composites were fabricated by 2 kinds of Hot Isostatic Pressing (HIP) conditions and elongated by 2 kinds of the following process by rotary swaging (RS), die forging (DF). The fatigue properties of these MMCs (metal matrix composites) were compaired with conventional Ti-6Al-4V alloy and HIP treated Ti-6Al-4V one. According to the results in the present study, the average hardness and fatigue strength of HIP-DF-0 showed higher values in comparison with those of conventional Ti-6Al-4V by about 20-30% and 15% respectively. However, the fatigue limit of MMCs was unexpectedly deteriorated in comparison to the conventional ones. The deterioration of the fatigue limit was considered to be due to the defects in the microstructure of the composites such as clustering of fibers, fiber orientation, micro-cracks and porosity.

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In this study, the influence of asymmetric triangular wave on fatigue life at eleveted temperature environment have been studied for PA66 resin materials. Especially the fracture mechanism has been analyzed for reliability. The main results are as follows; (1) There is the effect by the load waveform in the fatigue life of this materials. In the low stress side, fatigue lifes of the Fast-Slow wave are about 10 times in comparison with the Slow-Fast wave. (2) The fracture mechanism can be divided into three groups. In the high stress side, the fatigue factor control the fatigue life, and the waveform effect is little. In the low stress side, the creep factor control it. It is variable even in the inside waveform on the effect of creep. (3) There is the effect of the viscoelasticity by the load waveform.

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A new evaluation method was developed for low-cycle fatigue life for fork-type root attachments of long steam turbine blades. In this study, low-cycle fatigue life was estimated by calculating the micro crack growth life under a steep strain distribution, using the micro-crack growth rate, which is proportional to the effective crack length according to non-linear fracture mechanics. To verify this evaluation method, low-cycle fatigue tests on pin joint models were conducted, in which the crack growth behavior at the inner surface of the pin hole was observed by interrupting the tests. The estimated results for micro-crack growth behavior agreed well with the measured results. To obtain the local strain range distribution for fork-type root attachments, a two-step FEM analysis was proposed, including three-dimensional analysis of a whole-blade model and two-dimensional elastic-plastic contact analysis of a single blade-fork model.

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This paper presents a numerical technique for analyzing one-dimensional transient temperature distributions in a hollow circular cylinder of functionally graded ceramic-metal-based materials (FGMs) in relation to both the temperature-dependence and continuous/gradual variation of the thermal properties of the FGM, and also the related stress distributions are analyzed. The FGM cylinder is assumed to initially have a steady state of temperature gradient, having exposed to high temperature on the inner ceramic surface and to low temperature on the outer metallic surface associated with its in-service environment. The FGM hollow cylinder is then rapidly cooled on the inner ceramic surface by cold air. The transient temperature and stress distributions in the FGM hollow cylinder are analyzed numerically for a model of mullite-molybdenum system. The analytical technique of temperature distributions shown here is quite simple and widely applicable compared with methods previously proposed by other researchers.

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3-dimensional analysis of fracture surface using SEM (Scanning Electronics Microscope) is inevitable to clarify the cause of fracture. It is popular and effective to obtain fracture surface profile by stereo matching or by integrating secondary electron signals. The former method is advantageous because of its accuracy, and the latter method is advantageous because of its resolution; however, it is rather difficult to attain both accuracy and high resolution. Therefore, conventional methods cannot satisfy the accuracy of quantitative analysis in fractography. In this paper, a new method is proposed, which is the combination of the two methods. In this method, the height of stereo matching is revised with the inclinations measured by secondary electron signal intensity so as to lessen the error of stereo matching and obtain the real profile height of fracture surface. The error of proposed method is investigated and the results show that the method can improve the accuracy. A personal computer takes approximately six minutes to process one photograph.

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A method of improving mechanical properties of thin films by low energy ion irradiation treatment after the deposition was proposed in this study. The low energy Ar ion irradiation treatment is applied to aluminum thin films, which are widely applied to the MEMS and semiconductor device as conductive layers. Experimental results show that mechanical properties of the Al thin film deposited improved remarkably after the treatment. The surface of the Al thin films were irradiated with low energy Ar ions using Kaufman type ion gun for 30 minutes under the conditions: base pressure 1 × 10^-4 Pa, irradiation angle 90 degrees, acceleration voltagd 50 V and current density 0.1 mA/cm². The improvement is interpreted that Al atoms on the surface of the films were migrated due to kinetic energy of Ar ion irradiations and as the result: the bond strength in a direction of lengthwise was reinforced at the surface of Al films. The proposed treatment method is expected to improve surface mechanical properties of metal thin films deposited by various formation techniques and conditions, using selected irradiation treatment.

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A new method, combination of a boundary element method and a finite element method, has been developed to simulate the electroplating of a silicon wafer with copper. In this method, the Laplace equation is solved by representing the complicated phenomena near the anode and cathode surface as polarization characteristics (PCs) and using the PCs as nonlinear boundary conditions. The electrical resistance distribution of thin copper and TaN films on a silicon wafer is then taken into account. To make a uniform copper film, the anode (copper plate) is divided suitably into several pieces. To design the size of each multiple anodes rationally, the ideal anode current density distribution which is obtained by solving inverse problem are used. In the inverse problem both of the potential and the current density on the cathode are given as the ideal values, i. e., the uniform current density and its corresponding potential. Optimization of current to be supplied to each piece of the anode is performed by employing the Simplex method.

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Static load tests were carried out for component models and an experimental full-sized car body in which aluminum honeycomb panels are applied as outside plates to improve pressure resistance while their requisite light weight and rigidity are being kept. The results obtained are summarized as follows. (1) Tensile strength for general part of honeycomb panels were 240∼250 MPa. (2) Tensile strength for welded joint part of honeycomb panels were 194∼198 MPa. (3) Bending strength of a honeycomb panel was approximately 170 MPa. (4) Shearing strength of a honeycomb panel was at least 77 MPa. (5) Stresses of an actual car body were under 30 MPa. Then an actual car body has a sufficiency of the strength reliability.

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To evaluate the fatigue strength of an actual car body in which aluminum honeycomb panels are applied as outside plates to improve pressure resistance while their requisite light weight and rigidity are being kept, fatigue tests were carried out for component models (general part and welded joint part of honeycomb panels). The results obtained are summarized as follows. (1) Fatigue strength for general part of honeycomb panels was 60 MPa (at 1 × 10⁷ cycle). (2) Fatigue strength for welded joint part of honeycomb panels was 45 MPa (at 1 × 10⁷ cycles). (3) Stresses of an experimental full-sized car body were under 30 MPa. Then an actual car body has a sufficiency of the fatigue strength reliability.

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Fatigue test was carried out for an experimental partial full-sized car body and an experimental full-sized car body in which aluminum honeycomb panels are applied as outside plates to improve pressure resistance while their requisite light weight and rigidity are being kept. In reference to the test results, an allowable stress at the filet welded joint and honeycomb panel structures were evaluated under Miner's law. And this evaluated stress was reflected against a design and a manufacture of an actual car in reference to the number and value of varying pressure loads acting on the car body running in a tunnel which are calculated from a running test of the actual car.

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Numerical simulations of a rail car body crashing against a rigid wall were carried out, and deformation of the car body caused by collision was predicted. By comparison with a test of a fullscale model, it was proved that the crash energy was absorbed only by the deformation of car body end structure and that any part of compartment for the driver and passengers was not damaged.

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The distributed optimization method by resource addition and reduction, which is called the DORAR method, is a new optimization method for the minimization of the total resource of systems, and it has been found to be suitable for parallel processing and very robust for initial solutions. The only parameter in the method is the amount of the small additional resource used for increasing the resources of the elements of a system. It has been found that the amount of the additional resource can be determined from the required accuracy of final results. However, the problem on slow convergence still remains. This paper introduces three improvements for adjusting the additional resource aiming its fast convergence and the high accuracy of the converged solutions. One is the gradual reduction of the additional resource, one is the utilization of the sensitivity information, and one is the adaptation of the additional resource using the history of the resource reduction. These improvements are tested for optimizing truss structures and their effectiveness is examined.

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Buckling operation is frequently performed in clinic to treat the eyeball retinal detachment. However, the effect of operation heavily depends on the surgical experiences at present. In this paper, to numerically simulate this operation in order to predict the suitable conditions for clinical operation, a 2-D FEM program for coupling analysis of hyperelastic solid and static liquid is developed based on an incompressible hyperelastic program which was developed by authors for analysis of the soft tissues of livinghuman, and its effectiveness is demonstrated by a testing analysis. It is further applied to the simulation of the segmental buckling operation on an eyeball to qualitatively investigate the influence of the buckle shape, suture width and eyeball internal pressure on the operation. By this simulation, the useful results are obtained and it is expected that proper buckle effect will be available in clinical operation with the aid of these results.

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The relationships between the load peaks in load-displacement curves and the failure type of trabecular root in an interlaminar peeling process of a beetle fore-wing of A. Dichotoma were investigated and the interlaminar reinforcement mechanism was analyzed by using FEM. The peeling model with trabecular structure was proposed and the geometrical parameters for the model were determined by in-situ microscope observation. It was shown that the proposed model could be used to predict failure type of the trabecular root and to make clear the interlaminar reinforcement of a fore-wing. It was also found that the load peaks in a peeling process were proportional to the diameter of a trabecula, and depended on the failure type of the trabecular root. The principal stress at the peeling tip was very converged without the trabecula, but could eased by trabecula structure. It was shown that the fracture type of the trabecular root could be predicted by FEM model analysis.

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The mechanical properties, especially load-deformation relations under quasi-static and impact loading, of golf balls have been investigated. Dynamic compression tests have been conducted by the method that the ball is made to collide with the stress bar at velocities of 20∼65 m/s and the load-deformation curves are obtained by integrating the stress wave histories. The following results have been obtained. The load-deformation curves show non-linearity mainly due to geometrical factor and show hysteresis due to internal friction of the ball both under static and dynamic loading. The ratio of energy loss due to internal friction to input energy increases with the amount of deformation. In collision of the ball with the stress bar, only 70% to 45% of the initial kinetic energy is converted to the rebound kinetic energy. This ratio decreases with increase of the impact velocity. Among the rest of the energy, 25% to 45% is dissipated by internal friction, about 8% is transmitted as elastic wave energy to the stress bar and the rest several % remains in the ball as strain energy and vibration energy.

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