In this paper, we propose an effective finite element method (FEM) on the basis of domain decomposition method. In the domain decomposition method, the domain of structure is decomposed into subdomains, which are connected each other with an independent interface using a penalty function method. Using this FEM, the analysis of the whole structure can be carried out by analyzing the individual subdomain. As a numerical example, the stress analysis of an aircraft structural panel repaired with bonded composite patches is made, and the efficiency and the accuracy of the FEM are verified. The FEM is also used to carry out several parametric studies to examine the effects of patch shape and size on the stress fields in the repaired structural panel and composite patches. Finally, we determine the optimum shape and size of a composite patch to endure the maximum tensile applied stress by a mathematical programming.

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In this paper, we propose updated Lagrangian formulation of hyperelastic body, which has been formulated by total Lagrangian approach, and confirm the accuracy and stability of developed finite element analysis code. The referenced configuration of proposed hyperelastic constitutive equation consists with the configuration of elasto-plasticity for finite deformation by applying updated Lagrangian approach. So, both of constitutive equations can be treated simultaneously in analysis. Numerical results by updated Lagrangian formulation show higher stability under large deformation.

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The finite element mixed formulation of nonlinear viscoelasticity and material loading test results of high damping rubber material are presented to simulate mechanical properties of high damping rubber bearing. This finite element formulation is enable to deal with Simo-Taylor viscoelastic and damage model and compressibility of rubber material. Parameters of elastic potential function and damage model are obtained from material loading test. Simulations of horizontal properties of high damping rubber bearing are carried out to demonstrate the applicability of the finite element formulation.

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This paper presents the dual reciprocity boundary element method (DRBEM) for solving the steady-state heat conduction problem of temperature-dependent materials. The integral equation formulation uses the fundamental solution of the Laplace equation for homogeneous materials, and due to this fact a domain integral arises in the boundary integral equation. In this paper, this domain integral is transformed into a boundary integral based on the dual reciprocity introducing a new set of radial basis functions. An iterative solution procedure is used because material constant is temperature-dependent and hence nonlinear. The details of the proposed DRBEM are presented, and a computer code is developed for two-dimensional problems. Through comparison of the results obtained by the computer code with the exact ones, the usefulness of the proposed DRBEM is demonstrated.

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The meshless methods using node-by-node procedure is proposed to solve three-dimensional elastic problems. Meshless methods are expected to solve three-dimensional problems without time-consuming mesh generation process. In this paper, the node-by-node meshless method (NBNM), which discretizes the weak-formed governing equations of continuum mechanics using only distributed nodal data is applied to solving three-dimensional problems. This paper presents the formulation of the proposed method and numerical results for three-dimensional elastostatic and eigenvalue problems. It was shown that the proposed method is capable of simplifying the three-dimensional analysis data and solving elastic problems with the same accuracy as conventional FEM.

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Human creats the numerous kinds of gesture of different emotion by the motion and straining of the facial skin including the facial wrinklings. Basically, the deformation of the facial skin is mainly occurred by the contraction of the facial muscles under the skin. Therefore, it is necessary to clarify the mechanism of skin deformation behaviors induced by these contractions of facial muscle under various emotions. The determination of constitutive parameters in constitutive equation for active and passive mechanical properties of facial muscle is indispensable based on the experimental results. Here, to determine the parameters in constitutive equations of muscles, an experimental method in vivo state including measurement of the integrated EMG is proposed. Then, their constitutive parameters are identified based on the least square approach using the analogy with the FEM model. Finally, the validity of the identified results is discussed.

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We have developed an FEM tetrahedral-mesh generation technique for re-using an existing mesh in order to generate a new mesh after a change in 3 D-CAD data during parameter survey. Up to now, all meshes for updated 3 D-CAD data have been generated manually; however, the developed technique automatically uses a volume mesh and a surface mesh extracted from the existing mesh. It does this by recognizing the difference in the 3 D-CAD data before and after it is changed. As a result, mesh generation time is not wasted; that is, after the first mesh generation, the next generation times are shortened to 1/5 of the initial time.

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Rubber material is a most important component of seismic isolation bearing. Usually, this rubber has to be subjected to compression load, never tension because the heavy weight structure, e. g. building, is put on. Recently, the seismic isolation rubber bearing is applied to the light weight structure. On this case, the design will be considered that the bearing will be subjected to tension load because of structure tilt. Since the void nucleation due to tension affects the mechanical properties of this, it is important that the critical stress for void nucleation is to be clear. The cyclic tension tests are conducted for obtaining the variation of stress-strain relation using by thin rubber disk specimen modeled on a seismic isolation rubber bearing. After the tests specimens are cut and observed the surface configuration, especially void nucleation. Consequently, The stress-strain relation on first cyclic load has a hysteresis loop caused by void nucleation. Next, the stress distribution in the rubber disk under tension load are determined by FEM. From the comparison of experiment it is indicated that the triaxial stress is efficient for the parameter of void nucleation and the critical stress of void nucleation is determined.

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For composites containing NiTi fiber or Ti fiber in a polycarbonate (PC) matrix, uniaxial tensile loading-unloading tests were carried out. NiTi fiber shows psuedoelasticity (PE) at room temperature. Furthermore, the constitutive relation of shape memory alloy composites (SMAC) has been proposed taking visco-plasticity of the matrix into consideration, and some numerical simulations for the deformation behavior of NiTi/PC have been carried out under uniaxial tensile loading-unloading and thermo-mechanical loading. The overstress visco-plasticity model was used for visco-plastic matrix, and Brinson's model was used for shape memory alloy fiber. From the experimental and numerical results, the following conclusions are obtained. (1) The numerical results of the deformation behavior show good agreement with the experimental ones. (2) As compared with PE/Elasto-plastic composites, PE/PC composites exhibit psuedoelastic deformation behavior, while the compressive residual stress in the matrix after tensile loading-unloading is relatively low. (3) SME/PC composites show large contraction due to an elevation of temperature after tensile loading-unloading, while the compressive residual stress in the matrix is low.

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The importance of application of FEM to car crush has been increasing to evaluate the safety of cars and to reduce the cost of development expenses of cars. However, these analyses do not always correspond to the experiments because the analyses do not consider such effects of forming as residual stress, residual strain, and wall thinning that are caused by the manufacturing process. The purpose of this paper is to prove the necessity of analysis considering forming history of the manufacturing process on structural analyses. In order to investigate that, comparisons between analyses and experiments on hydroformed member in various conditions were carried out. Comparing analytical results with experimental one, crush load of the model that is used in this study could be more exactly predicted by considering the forming history. As the results, it is important to consider the forming history in order to estimate the crush characteristics accurately.

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The present paper proposes a novel approach for the identification of the material parameters of elasto-plasticity for individual component layers of a bimetallic sheet. This method has an advantage of using the experimental data (tensile load vs. strain curve in the uniaxial tension test and the hending moment vs. curvature diagram in the cyclic bending test) for a whole bimetallic sheet but not for individual component layers. A set of material parameters in each of two types constitutive models of cyclic plasticity (the Chahoche-Rousselier model and the Prager model) for individual component layers were identified by minimizing the difference between the experimental results and the corresponding results of numerical simulation. An optimization technique based on the iterative multipoint approximation concept was used for the identification of the material parameters.

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SPH (Smoothed Particle Hydrodynamics) method, which is one of the meshless analysis, has been proved as a powerful tool for structural analysis especially in hyper-velocity impact problems. Recently the method has been shown to have much potentials for general dynamic structural problems, however, the applications have not been sufficient because the theory for plastic analysis in SPH has not fully developed. In this study elastic-plastic analysis of SPH in 2 -dim has investigated to clarify the accuracy and characteristics of this method. Two elastic-plastic models have been used. One is so called [D^p] matrix method (strain-rate independent model) and another is Johnson-Cook Model (strain dependent model). The results have showed that elastic-plastic SPH analysis has good accuracy in comparison with FEM and presented reasonable solutions in time-dependent and time-independent problems in 2 dimensions.

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The indirect fictitious-boundary integral method is applied to two-dimensional unsteady elastodynamic problems. At first, the impulsive stresses are analyzed for a circular hole in infinite medium subjected to impulsive pressure at the surface boundary, and this result is compared with the analytical solution. Next, the longitudinal impact problem of a strip with a semi-circular notch is treated, and the dynamic stress concentration factor and the stress distribution are accurately analyzed. Finally, the availability of this method to two-dimensional unsteady elastodynamic problems is shown.

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It is known that each stress component is intensified at the tips of an anticrack (rigid line inclusion) as well as a crack, proportionally to γ^-1/2. This paper deals with the numerical method of the singular integral equations of the Cauchy type for the analysis of stress-singularities at anticrack tips by using the body force method. In the singular integral equations, the densities of the body forces which should be distributed along the anticrack surfaces are to be obtained so that the boundary conditions on the anticrack surfaces can be satisfied. The numerical method of the singular integral equations is based on the Lobatto-Chebyshev integration formula. In order to demonstrate the effectiveness of the proposed method, some numerical examples are given. The calculated stresssingularities at anticrack tips converge very fast with the increase of the number of the collocation points and some of them are compared with the exact solutions in order to verify the accuracy.

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The effects of compacting pressure and sintering temperature on elastic moduli of sintered irons for reduced and atomized iron powders were investigated. The elastic moduli were mainly depended on porosity. The porosity decreased exponentially with increasing compacting pressure and was independent on sintering temperature. However, hecause the pore surface becomes smooth and the open porosity decreases with increasing sintering temperature, Young's modulus and shear modulus increased slightly at the equal porosity. It is clarified that the critical porosity exists where the downtrend of elastic moduli changes and increases with sintering temperature. Furthermore, the new equations of elastic moduli against kinds of iron powder, compacting pressure and sintering temperature that can be controlled on manufacturing of sintered parts, were deduced. The good correlation between calculated data by using of the equation with considering of the critical porosity and experimental data was obtained.

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It is very important in the industrial field to examine mechanical and fatigue life properties of small materials such as thin films. Some kinds of test equipment and methods for such small material have been developed. For example, there are simple and compact tensile testing devices that use a DC motor as the actuator, and also micro indentators, which measure material properties by pushing a diamond indentator on the surface. However, it is still difficult to conduct a fatigue test with complex waves like a triangle wave by the above testers. In this study, a small fatigue testing device, in which a piezo electric ceramic is applied as the actuator, was produced as a trial for measuring a tensile strength and fatigue life properties of a small material. Through our tests, it was found that the small fatigue testor which was developed here is effective for small specimens. Results showed that a yield stress and tensile strength for our film material was much higher than for SUS304 bulk material, which we had tested previously. The fatigue life was also much higher than for the bulk.

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In order to investigate the effect of the constraint of deformation at an interface on the slip behavior, a test is carried out at room temperature in high-cycle fatigue of a two-phase (α/γ) stainless steel bicrystal, which consists of ferritic (Fe30Cr) and austenitic (Fe15Cr15Ni) single crystals, with a longitudinal interface parallel to the load axis. In this bicrystal, the active slip direction intersects the interface. Since the yield stress of α-phase is much higher than that of γ-phase, the slip takes place only in the γ-phase. Not only primary slip lines expected from the crystallographic orientation but also additional slip lines are observed in the γ-phase near the interface. The stress distribution is analyzed by a finite element method (FEM). It shows that the resolved shear stress, τ_rss, on the specific slip system near the interface increases, and the activated slip system corresponds to the additional slip experimentally observed. The region where the additional slip are observed agrees well with the one where the resolved shear stress exceeds the critical stress of the γ-stainless steel single crystal. This signifies that the characteristic slip behavior near the interface is attributed to the increase of τ_rss due to the constraint of deformation.

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The influence of tensile pre-strain on a fatigue crack initiation and propagation behavior of a squeeze cast Al alloy, AC 4 CH-T 6, was investigated under rotating bending in comparison with that of wrought Al alloy, 6061-T 6. Fatigue strength was a little or not influenced by tensile pre-strain in both alloys. However, both the crack initiation and its propagation were influenced by pre-strain and the influence was different in the alloys. That is, in cast Al alloy, both the crack initiation and the early propagation of a shear mode crack were accelerated by pre-strain, though the influence was negligible in wrought Al alloy. On the other hand, the propagation of a tensile mode crack was suppressed by pre-strain in both alloys. The main reason for the acceleration of crack initiation in the cast Al alloy was an interface cracking or a weakening between eutectic Si particles and matrix by pre-strain.

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This paper is concerned with the numerical analysis of dynamic thermal stress and deformation for moderately thick shells of revolution made of functionally graded material by using finite element method. The material properties of the shell are continuously inhomogeneous along the shell thickness and dependent on the temperature. The temperature distribution through the shell thickness is expressed with a curve of high order, and thick shell elements are utilized for the analysis. As numerical examples, two kinds of functionally graded material shells composed of SUS 304 and PSZ subjected to thermal loads due to heat generation in the shell bodies are treated; one is a cylindrical shell and another is an axisymmetric shell having a parabolic meridian. In comparison with the results from the characteristic method, good agreement is obtained. And it is found that temperature distributions, stress distributions and deformations are significantly influenced by temperature dependent properties of the materials.

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In this paper, we discuss the recursive optimal design approach: an application of self-similarity to optimal structural design. The approach is formulated in a recursive manner based on a resourcebased optimization concept. An actually self-similar topology of the initial truss structure is introduced in order to realize a completely self-similar optimization process. Computational cost and suitability to parallel processing of the recursive optimal design approach are discussed from the view-point of self-similarity. Minimum-weight design of two-dimensional truss structure is conducted; the availability of the actually self-similar topology of the truss to the recursive optimization process is also discussed.

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In assuring the safety of a structure, it is important to evaluate the state of structural members non-destructively by magneto-mechanical acoustic emission (MAE). MAE is useful in NDT, because it reflects minute changes of stress and microstructure of ferrous materials. We studied MAE signals of a pure iron using displacement and shear sensors, for the detection of the longitudinal and shear components of the signals, which were analyzed by wavelet transform. The mapping of wavelet coefficients in the time-frequency coordinate plane provides informative characterization of the signals. From the analysis, we found that the low (150 to 300 kHz) and high frequency (400 to 800 kHz) components are caused by different magnetization effects. The low frequency component has strong displacement sensor response coincident with the rate of magnetic induction, suggesting magnetization via the discontinuous motion of domain walls. The high frequency component has strong shear sensor response and is observed near magnetic saturation, suggesting rotational magnetization effect.

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Our objective is to develop an effective method for measuring deformation in small solder ball joints. We focused on the Zeebeck Effect, which is characterized by electromotive force (E_mf) in thermo-coupling and tried to measure E_mf when the solder ball was deformed. A Cu wire-Solder ball-Cu/Ni wire arrangement was made. Usually a thermocouple connection for temperature measurement has two different metal wires directly facing each other. But, for our experiments a third metal, i.e., solder, was sandwiched between the two-thermocouple wires. The diameter of the solder ball was 1.3 mm. When an E_mf was generated and measured at various deformation speeds of the solder ball, we found that the E_mf increased as the deformation increased. Furthermore, the E_mf changed in relation to the load cycling magnitude. We demonstrated that the proposed E_mf measuring method can be a useful and powerful tool for the deformation evaluation of real solder connections.

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