When the piezoelectric film is glued on the surface of a cracked material subjected to mechanical load, change in distribution of electric potential is observed on the surface of piezoelectric film. Based on this phenomenon, passive electric potential CT(computed tomography) method was developed for the identification of two- and three-dimensional cracks based on the FEM inverse analysis. In this paper, this method was applied to identify 3-D surface crack opening on the back surface. Numerical simulations were carried out on determination of location and size of back surface crack. It was found that crack parameters were identified within the error of 1.0%, when the noise level of observed electric potential distribution was lower than 0.1%.

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The developments of hydrogen production equipment using inorganic membrane have been conducted to separate hydrogen from feed gas. A reactor vessel had been used for the purification of hydrogen in the hydrogen production process. The reactor vessel consists of a long vessel including pipe and catalyst balls, and then the space between the pipe and the vessel is filled with small catalyst balls. It is difficult to examine the stress state of the pipe in the vessel when the vessel is bent by mechanical and thermal loads in the operation. Because the section packed the catalyst balls isn't a continuum and the catalyst balls can't be transmitted the forces to separate in tensile state. In this paper, a method was proposed to identify the effective material constants of the section packed the catalyst balls in the vessel. The validity of the proposed method was confirmed by numerical simulations and experiment.

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Authors have proposed a new nondestructive method of evaluating welding residual stresses, the Bead Flush Method, and confirmed its validity for simple butt-welded plates. In this method, eigen-strain distributions are estimated from strain changes due to removal of reinforcement of the weld using the inverse analysis. Then, residual stresses are estimated by the elastic FEM (Finite Element Method) analysis using estimated eigen-strain distributions as initial strains. In this study, further development of this method was attempted for application to welded pipes. Eigen-strain distributions in welded pipes are more complicated than those of welded plates from a view point of residual stress estimation. Based on a previous research, a further formulization was attempted to overcome this difficulty and problems to be solved were made clear.

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Multilayer coatings are widely used to various optical parts, for example, multimode optical fibers, beam splitters, antireflection coatings. For another applications, multicoated thin films on solar panels have capabilities to control the solar energy by means of spectrum transmittance and reflectance control. In this paper, we discuss the design specifications for the function of solar panel. In the design of optical multilayer coatings, refractive index and thickness of each layer must be determined in accordance with the specifications on spectral reflectance. The solar spectrum, the culmination altitude and conditions of the production process for coatings must be considered. To solve the problem, our developed design system is used for optimum design. Obtained optimum design results for less severe design specifications are shown.

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The purpose of this paper is to present a numerical algorithm for the problem of the coefficient identification of the scalar wave equation: Determine the unknown coefficient function with the knowledge of simultaneous Dirichlet and Neumann data. We introduce a functional to be minimized and recast our problem to a variational problem. To find the minimizing function, we use the alternating directions method. We confirm the effectiveness of our algorithm by numerical experiment.

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In this paper, we study inverse kinematics problems in which the trajectories of walking robot toes are generated under the condition of minimum walking energy. It is important for a walking robot that motions of legs are determined to achieve a desired body motion. A 4-legged walking robot with two rinks and two motors at joints of waist and knee is assumed in this study. A mathematical optimization method is used for the optimization of several parameters which describe the trajectory function of toe. A fuzzy clustering is applied to select teaching data for neural networks to obtain trajectory parameters. Some trained neural network controllers are applied to each obstacle by switching over.

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An efficient numerical method is proposed for three-dimensional corrosion analysis of structures having net geometory, such as rebar in concrete, fence with sea-side structure. The knowledge of physical quantities (potential and current density) on the surface of corroding materials is very important in corrosion monitoring and corrosion protection. Boundary element method is suitable for corrosion analysis, because it doesn't require discretization of internal domain. Enormous number of elements is necessary to discretize the structure having net geometory. To reduce the number of boundary elements, our method is based on complex Fourier series expansion of boundary quantities in circumferential and axial direction of net structures. In order to demonstrate the usefulness of the method, Example problem of rebar in concrete with cathodic protection system are presented.

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An iterative domain decomposition method for the numerical solution of an external problem of the Helmholtz equation is considered. An artificial boundary decomposes the external domain Ω into a bounded subdomain Ω_1 and the unbounded subdomain Ω_2 outside Ω_1. We apply the Dirichlet-Neumann map on the boundary. The finite element and the boundary element methods are used for the discretization of the equations on the domains Ω_1 and Ω_2 respectively, and the methods are indirectly combined by the nodal data along the artificial boundary. Numerical examples show that our method is applicable for low frequency waves and the upper limit of tractable frequencies depends in polynomial order on the radius of the artificial boundary.

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This paper describes the application of the Trefftz method to the simulation of the sloshing phenomenon in the two-dimensional rectangular vessel. The phenomenon can be modeled as the initial and the boundary value problems of the Laplace equation with respect to the velocity potential. The equation is solved to determine the fist- and the second-order derivatives of the potential on the fluid surface. The initial value problem is solved by the scheme using both velocity and acceleration which are estimated from the potential derivatives. Finally, the present scheme is applied to the simulation of the sloshing phenomenon on the fluid in the two-dimensional rectangular vessel.

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We deal with a pulsatile flow in a two-dimensional stenosed blood vessel using the Cartesian coordinate system. In this paper we assume that some voxel data are given. We determine the boundaries of the domain in a manner of VOF (fractional volume of fluid) and use the non-staggered finite difference method and the neighboring point local collocation method (NPLC) for the spatial discretization. The numerical results obtained by the present method are in good agreement with other reliable results.

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