This paper is concerned with the application of the boundary element method with the analog equation method (AEM), proposed by Katsikadelis and Nerantzaki, and Green's theorem to analyze steady-state heat conduction in anisotropic solids. In this study, the linear differential operator (the Laplacian) of steady-state heat conduction in isotropic solids is extracted from the governing differential equation. The integral equation formulation employs the fundamental solution of the Laplace equation for isotropic solids, and therefore, from the anisotropic part of the governing differential equation, a domain integral arises in the boundary integral equation. This domain integral is transformed into boundary integrals using Green's theorem with a polynomial function. Mathematical formulations of this approach for two-dimensional problems are presented in detail. The proposed solution is applied to two typical examples, and the validity and other numerical properties of the proposed BEM are demonstrated in the discussion of the results obtained.

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When analyzing the strength of large structures, the stiffness of the foundation, on which the structure is placed, might significantly affect the numerical results. In order to take account of the foundation stiffness, therefore, the lower surface of the structure, which is in contact with the foundation, is frequently treated as spring-supported boundaries. Meanwhile, it is not necessarily easy to estimate the foundation stiffness with sufficient accuracy for the purpose of implementing numerical analyses. In this paper, a finite element approach to estimate the foundation stiffness as an inverse problem is proposed, where the target large structure is placed on the elastic foundation that are modeled as groups of one-dimensional spring elements in parallel. The magnitude of the spring constant that represents the foundation stiffness can exactly be calculated algebraically in terms of the same number of measured surface displacements. In the numerical analyses, unknown are the diagonal components of the global stiffness matrix that include the effect of the foundation stiffness. The validity and the accuracy of the proposed numerical method are verified by comparing the numerical results to the exact solutions for a bending problem of a cantilever that is supported by a single spring element.

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Copper electroplating is generally used for the fabrication of Large-Scale Integration (LSI) besides other methods such as sputtering because of its excellent via/trench filling ability, good adhesion and lower process temperature and cost. In the electroplating process, estimating a growth rate of electroplating in real-time is essential. It is possible to estimate a growth rate of electroplating from the current density on the LSI wafer surface because the rate mainly depends on the current density. In our previous research, applying inverse analysis methods, a new nondestructive method to monitor a growth rate of electroplating from the magnetic flux density outside the electroplating device measured by magnetic sensors was developed. In this paper, measurement experiments under several electroplating conditions are performed in order to verify the effectivity of this method. The growth rates of electroplating estimated by the method are compared with the thicknesses measured by the profilometer. Also the electric potentials in the electroplating device estimated by the method are compared with those measured by the electrometer. These results show that this method could be applicable to practical problems. In addition, we extend the method for an arbitrarily shaped electroplating device by applying FEM and BEM. We apply Tikhonov regularization to this method and develop a new determination procedure of the regularization parameter

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A new identification method with micro/nano-indentation for plastic material parameters of film/substrate system is presented. The method is based on extensive finite element computation on, “soft film on hard substrate” cases indented with cone. The method also utilizes the substrate effect on load versus depth relation in the indentation, this effect has often been regarded as undesirable. The computational results were expressed as a response surface in a material parameter space. Based on the surface, and employing experimentally obtained load versus depth relation, the plastic material parameters of the film are identified. A numerical example determined by this method for different plastic properties of film/substrate system is given.

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Damage detection has received much attention for structural health monitoring. In this paper, we develop a damage detection method for truss structures using a neural network with relearning process. The damage of truss structures is characterized as reduction of mass and stiffness of truss member. The input data are composed of the frequencies and mode shapes of damaged truss structure. To verify the validity and effectiveness of the present method, the damage detection is conducted using the input data without measurement errors, and the results of the damage detection are compared with the exact ones and those by previous damage detection methods. Consequently, it is found that the present method can identify satisfactorily the location and magnitude of damage. Finally, the damage detection is conducted using the input data with measurement errors. It is recognized from the results that the present damage detection method is effective in practical use.

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The electrochemical-poroelastic bending behavior of conducting polymer actuators is an attractive feature, considering their potential applications such as artificial muscles or MEMS. In the present study, a computational modeling is presented for the bending behavior of polypyrrole-based actuators. The one-dimensional governing equation for the ionic transportation in electrolytes given by Tadokoro et al. is combined with the finite element modeling for the poroelastic behavior of polypyrroles considering the effect of finite deformation. The validity of the proposed model has been illustrated by comparing the computed results with experimental results in the literatures.

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In this paper, the elastoplastic bending collapse of cylindrical tube subjected to statically pure bending is studied by using finite element method (FEM). It is revealed in the case of infinite length that the moment of the elastoplastic cylindrical tube is controlled by flattening ratio of tube. Also, it is shown that the flattening ratio of tube can be expressed by axial and circumferential stress as a function of the material and geometrical properties and curvatures. Based on these facts, an approximate numerical method to estimate the maximum moment of cylindrical tubes is proposed, and its validity is shown by comparing with numerical results of FEM.

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In this paper, in-plane equivalent elastic modulus Ey of a hexagonal honeycomb sandwich, which includes the effect of face sheet interference, is studied by using numerical results of FEM. It is shown by comparing with deformation of practical honeycomb sandwich that there are two error factors to apply the rule of mixture to honeycomb sandwich. One of error factors is that the deformation of honeycomb core does not coincide with the face sheet since an inclined cell wall deforms much larger than a vertical cell wall. Another one is that the non-uniformity deformation of core along the height direction is induced by the interference effect with face sheet. Then, a method to calculate elastic modulus based on the compatibility condition of core and face sheet is proposed, and its validity is verified by using numerical results of FEM.

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A Material, which has zero or very small thermal expansion coefficient, is expected in parts for precision machines and optical instruments. An analytical model for a short fiber composite is developed to evaluate thermal expansion coefficients by applying the Eshelby's equivalent inclusion method to two kinds of inhomogeneities, i.e. fiber and filler. It is assumed that the inhomogeneities distribute uniformly within the limits of an arbitrary orientation angle in the 2-D plane. Good agreement between the theoretical results based on the present model and experimental ones is obtained. The effects of distributions of fiber-orientation, fiber-aspect ratios, volume fractions and Young's moduli on thermal expansion coefficients are investigated for a carbon fiber/epoxy resin composite. The possibility of realizing zero and very small thermal expansion coefficients in the short-fiber composite is shown in case that fiber-aspect ratios are relatively large and fibers are almost aligned.

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On the basis of hyperelastic material behavior various forms of the strain energy density function, depending either on the invariants of the right Cauchy-Green deformation tensor. If a material behaves transversely isotropic behavior with respect to the reference configuration, then the strain energy function can depend on five principal invariants. Five principal invariants are ordinary three invariants and additional fourth and fifth invariants. In the area of automotive belt designing technique, the most material of belt is constructed be fibre reinforced hyperelastic. In this paper, we propose the polynomial strain energy function and determinate its material constants for the fibre reinforced material.

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A virtual crack closure-integral method (VCCM) for the generalized finite element with drilling and strain degrees of freedoms (DOFs) is presented in this paper. Free mesh method (FMM) is one of useful methods for fracture mechanics analysis. However, in FMM, quadratic elements with mid-side nodes cannot be employed due to restrictions arising from its local mesh generation rule around each node. Generalized elements with drilling and strain DOFs which have no mid-side nodes may improve the accuracy in fracture mechanics analysis over the conventional constant strain elements. Present authors have proposed a VCCM for two-dimensional generalized elements with drilling DOFs, in their previous papers. In this paper, in order to improve the accuracy in fracture mechanics analysis further, we present a VCCM for generalized finite element with drilling and strain DOFs. Finally, some numerical examples are presented and it is demonstrated that the generalized element with drilling and strain DOFs has superior accuracy over that with drilling DOFs only.

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In order to investigate fatigue characteristics of vulcanized natural rubber (NR), fatigue tests are carried out under various stress ratios R and variable loading. In this paper, fatigue crack propagation life is predicted depending on fatigue crack propagation behavior, because the fatigue life is almost the fatigue crack propagation life. Two essential assumptions for the application of Miner's rule are satisfied. It is considered that Miner's rule can predict the fatigue life safely under two-step loading, because the fatigue damage location is depending on R. Under complex variable loading, it is considered that the crack growth rate under 0<R<1 condition is accelerated because of disappearance of crystallization effect. So, it is necessary to make up the modified constant life diagram. The fatigue crack propagation life can be predicted using the modified constant life diagram and Miner's rule.

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Fatigue tests have been conducted to investigate the influence of irreversible hydrogen and its activation energy for hydrogen desorption from trap site on the fatigue strength for cold-drawn high strength steels with different activation energy, but having the same chemical composition. Specimens were cathodically hydrogen charged, and internal hydrogen states were changed as follows : (a) non-charged sample and (b) the one that contained only irreversible hydrogen. Since the fatigue crack was initiated at internal inclusion or microstructural inhomogeneity, the fatigue strength was discussed based on the stress intensity factor calculated from stress and defect size. In the case of the sample with higher activation energy, 71.4 kJ/mol, irreversible hydrogen had no influence on the fatigue strength. In this case, the fracture surfaces of the sample with and without irreversible hydrogen were the same. However, for the sample with lower activation energy, 60.3 kJ/ mol, the fatigue strength of the specimen having only irreversible hydrogen decreased compared with non-charged specimens. The fracture surface of the sample with irreversible hydrogen was brittle compared with that of non-charged sample. This indicates that the influence of irreversible hydrogen on the fatigue strength tends to become small with increasing activation energy for irreversible hydrogen desorption.

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We previously developed a crack propagation model that can be used to calculate crack paths in micro-solder joints in semiconductor structures. We have now developed a method based on this model that can be used to predict solder fatigue life. Correcting for the effect of element size is difficult when fatigue life is calculated using a finite element method, so we investigated the dependence of the calculated life on the element size and developed a formula for approximating this dependence using Hutchinson-Rice-Rosengren singularity theory. This formula enables us to estimate fatigue life regardless of element size. We tested this formula by analyzing the effect of element size on the fatigue life of a center-cracked plate (CCP) made of tin-lead eutectic solder. The results agreed well with the experimental results, indicating that our method can effectively predict solder fatigue life.

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We previously developed a crack propagation model to calculate crack paths using accumulated damage in microsolder joints in semiconductor structures. We have now developed a method based on the crack propagation model, which is named accumulated damage model, to predict fatigue-crack propagation properties of solders. Generally, there is a correlation between crack propagation rates, da/dN, of solders and J-integral ranges, ΔJ. The correlation can be represented in an equation as a simple power relationship, given by da/dN=B [ΔJ] ^q. We derive this simple power equation from our crack propagation model and Hutchinson-Rice-Rosengren singularity theory. The equation enabled us to estimate fatigue-crack propagation properties from cyclic stress-strain curves and fatigue strength properties. We used the method to predict fatigue-crack propagation properties for center-cracked plate specimens made of Sn-40Pb and Sn-3.5Ag-1Cu. The predictions agreed well with actual fatigue-crack propagation properties determined by experiment for center-cracked plate specimens made of Sn-40Pb and Sn-3.5Ag-1Cu, indicating that our method effectively predicts solder fatigue-crack propagation properties.

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It is well known that the inelastic strain accumulation of statically determinate structure subjected to forced displacement is caused by the elastic follow-up due to surrounding elastic region. The author once showed that the relaxation phenomenon of creeping structures during the elastic follow-up can be well estimated by the reference stress method. By applying this result, the author has proposed a simplified method to estimate the creep strain accumulated by the elastic follow-up. It has been shown that elastic follow-up factor can be calculated from the reference stress ratio, which is the ratio of Local Reference Stress and Global Reference Stress. The proposed method was applied to the elastic follow-up of 2-bar model and 2-beam model. For 2-beam model, a simple method has been proposed to estimate the stress-strain relation during the elastic follow-up, and it showed quite good agreement with FEM results. It was also shown that the proposed method can be applied to the plastic strain accumulation due to the elastic follow-up. By comparing with other strain estimation methods such as Neuber's method and Stress Relaxation Locus method, the proposed method was found to be reasonable and precise.

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Internal strain and stress distributions of carburized transmission gear was non destructively measured by neutron diffraction in order to understand deformation behavior after carburizing. The material used in this study was chromium-molybdenum steel, SCM 420 H. The carburized case depth was determined by microscope and measuring hardness distribution. The diffractions from Fe-110 and 211 planes were used, and internal strain was obtained from the lattice spacing change. Reference coupon specimens were cut from the same carburized gear, and then lattice spacing was measured as stress-free one. As the results, the carburized case depths of shift fork groove and dog clutches were relatively deeper than that of gear wheel. From measured axial, radial and hoop residual strains near the internal spline, large tensile residual strain parallel to the axial direction was generated in the shift fork groove. Furthermore, tensile residual strains parallel to the axial and hoop directions were also generated in the gear wheel. Residual strains of carburized gear were found to be not uniform, and be balanced by local deformation through the whole gear including the shift fork groove and dog clutches.

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Cavitation erosion resistance was studied for duplex stainless steels (DP33, DP37 and DP38) and super duplex stainless steels (DP40 and DP42) using a vibratory apparatus in distilled water and seawater. In comparison with the effect of the difference of the component element content on cavitation erosion resistance, following facts were clarified. Cavitation erosion resistance of the duplex stainless steels and the super duplex stainless steels in the distilled water and P.I. value which showed the corrosion-resistance did not show the good correlation. Cavitation erosion resistance in distilled water and seawater showed the good correlation with Vickers microhardness (HV) which was obtained from the ratio of ferrite phase to austenite phase and each hardness by a composite rule, and the cavitation erosion resistance are improved when the hardness increases.

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In this paper, a three-dimensional digital human-head model was developed and several dynamic analyses on the head trauma were conducted. This model was built up by the VOXEL approach using 433 slice CT images (512×512 pixels) and made of 1.22 million parallelepiped finite elements with 10 anatomical tissue properties such as scalp, CSF, skull, brain, dura mater and so on. The numerical analyses were conducted using a finite element code the authors have developed. The main features of the code are 1) it is based on the explicit time integration method and 2) it uses the one point integration method to evaluate the equivalent nodal forces with the hourglass control proposed by Flanagan and Belythcko and 3) it utilizes the parallel computation with the MPI. In order to verify the developed model, the head impact experiment for a cadaver by Nahum et al. was simulated. The calculated results showed good agreement with experimental ones. A front and rear impact analyses were also performed investigate the relation between the impact direction and the positions of the high measurement of pressure and stresses in brain. The obtained results represent that brain injury has a closer relation with the Mises equivalent stress rather than the pressure. At this time, the large deformation of a frontal cranial base was observed in both frontal and occipital impact analyses. We expect that it induces the brain injury in a frontal lobe regardless of the impact positions.

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In order to evaluate the influence of injury to the intervertebral disc, supraspinal ligament, interspinal ligament, and facet joint on the spinal deformation, we conducted a bending test in a total of 8 directions and a torsional test using the 6-axis material testing machine we developed for this study. The study closely investigated changes in the range of motion (ROM) of the functional spinal unit (FSU) associated with injury using a FSU of the lumbar spines obtained from human cadavers. The results of the bending test showed that when the intervertebral disc was injured, the ROM increased equally in all directions. When the supraspinal ligament and interspinal ligament were injured, the ROM increased only in the flexion. When the facet joint was injured, the ROM increased in the flexion and extension. The results of the torsional test showed that when the facet joint was injured, the ROM increased remarkably. Furthermore, the coupled motion to lateral direction was recognized in the models with the facet joint.

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Microstructure, hardness and wear resistance of WC/Co coatings prepared by cold spraying and influence of powder properties, such as powder size, WC particle size and cobalt content, on those properties have been investigated in this study. Both smaller WC particle and low cobalt content are found to be effective to produce dense, hard and highly wear resistant coating. Smaller powder size is also favorable to make a coating with high mechanical properties. The cold sprayed coating using WC (0.2μm) /12% Co with powder size of -20+0μm has best mechanical properties within this study. This coating has high density compared to conventional HVOF sprayed coatings. Its abrasive wear resistance has been almost comparable to HVOF coating. Strong correlation is also seen between hardness and wear resistance.

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