Yoshihiro Ootao

Analytical technique for electroelastic field in piezoelectric bodies belonging to point group D

To elucidate the electroelastic field in woods, which are piezoelectric bodies belonging to point group D∞, we construct an analytical technique for general solutions to electroelastic problems in these bodies. First, the constitutive equations are derived considering the microstructures and their combined behaviors. Then, the displacement and electric field are expressed in terms of two types of displacement potential functions and the electric potential function, and their governing equations are obtained using the fundamental equations for the electroelastic field. As a result, the electroelastic field quantities are found to be expressed in terms of four functions, namely two elastic displacement potential functions and two piezoelastic displacement potential functions, each of which satisfies a Laplace equation with respect to the appropriately transformed spatial coordinates. As an application of the technique, the electroelastic field in a semi-infinite body subjected to a prescribed electric potential on its surface is analyzed, and the numerical results are illustrated. This novel technique serves to investigate the electroelastic field inside wooden materials.

Transient Thermoelastic Analysis for a Multilayered Hollow Circular Disk with Piecewise Power Law Nonhomogeneity

This article is concerned with the theoretical treatment of transient thermoelastic problem involving a multilayered hollow circular disk with piecewise power law nonhomogeneity due to uniform heat supply from inner and outer surfaces. The multilayered hollow circular disk is cooled from the upper and lower surfaces of the each layer with constant heat transfer coefficient. The thermal conductivity, the Youngs modulus and the coefficient of linear thermal expansion of each layer are expressed as power functions of the radial coordinate, and their values continue on the interfaces. We obtain the exact solution for the one-dimensional temperature change in a transient state, and in-plane thermoelastic response under the state of plane stress. Some numerical results for the temperature change, the displacement and the stress distributions are shown in figures.

Transient Thermal Stress Problem of a Functionally Graded Magneto-Electro-Thermoelastic Hollow Cylinder Due to a Uniform Surface Heating

This article is concerned with the theoretical analysis of the functionally graded magneto-electro-thermoelastic hollow cylinder due to uniform surface heating. We analyze the transient thermal stress problem for a functionally graded hollow cylinder constructed of the anisotropic and linear magneto-electro-thermoelastic materials using a laminated composite model as one of theoretical approximation under a plane strain state. As an illustration, we carry out numerical calculations for a functionally graded hollow cylinder constructed of piezoelectric and magnetostrictive materials and examined the behaviors in the transient state. We investigate the effects of the nonhomogeneity of material on the stresses, electric potential, and magnetic potential, and the effect of the applied electric potential on the thermal stress σθθ.

Transient Thermoelastic Analysis for a Laminated Composite Strip with an Interlayer of Functionally Graded Material

This paper is concerned with the theoretical treatment of transient thermal stress problem involving a laminated composite thick strip with an interlayer of functionally graded material due to nonuniform heat supply in the width direction. The thermal and thermoelastic constants of the interlayer of functionally graded material are assumed to vary exponentially in the thickness direction. We obtain the exact solution for the two-dimensional temperature change in a transient state, and thermal stresses of a simple supported strip under the state of plane strain. Some numerical results for the temperature change, the displacement and the stress distributions are shown in figures. Furthermore, the influence of the thickness and position of the interlayer is investigated.

Electroelastic Response of Cylindrical Fiber with D∞ Symmetry Exposed to Local Electric Field Through Opposed Electrode Pair

ABSTRACT To obtain practical information on the electroelastic behavior of poly-l-lactic acid microtweezers or catheters, a previously constructed analytical technique is used to obtain the electroelastic field solution of a poly-l-lactic acid cylindrical fiber exposed to a local electric field, which is applied through an opposed pair of square-sectioned electrodes. The numerical representation of the solution reveals the detailed field quantity distributions, their importance in the design of microtweezers and catheters, the overall deformation of such devices, and the effects of the electrode dimensions on the deformation. GRAPHICAL ABSTRACT

A general solution technique for electroelastic fields in piezoelectric bodies with D∞ symmetry in cylindrical coordinates

To elucidate the electroelastic field in bodies with D∞ symmetry such as wooden materials, we constructed a general solution technique for electroelastic problems in such bodies in a cylindrical coordinate system. We introduced the displacement and electric potential functions to express the displacement and electric field in cylindrical coordinates; their governing equations were obtained using the fundamental equations for the electroelastic field. The electroelastic field quantities could be expressed in terms of two elastic displacement potential functions and two piezoelastic displacement potential functions, each of which satisfies a Laplace equation with respect to the appropriately transformed cylindrical coordinates. As an application of the technique, we analyzed the problem of an infinitely long cylinder subjected to a non-axisymmetrically distributed electric surface potential. Using numerical calculations, we elucidated the electroelastic field quantities within the cylinder and found unique electroelastic coupling behaviors, which clearly demonstrate the necessity for the analytical technique presented. Moreover, we confirmed the possibility of the nondestructive evaluation (NDE) techniques by use of the piezoelectric effects.

Hygrothermal Field Considering Nonlinear Coupling Between Heat and Binary Moisture Diffusion in Porous Media

The hygrothermal field in porous media exposed to heat and moisture considering nonlinear coupling was studied. Dissolved and gaseous phases with different diffusivities were used to model the moisture in solids and voids, respectively. Heat generated by the transformation of gaseous moisture into dissolved moisture was considered along with the transformation from dissolved moisture into gaseous moisture due to a change in temperature. The balance between dissolved and gaseous moistures is determined by the chemical equilibrium. A system of nonlinear coupling diffusion equations was derived, and a steady field for an infinite strip was demonstrated.

Genetic Algorithm Optimization for Tensioning in a Rotating Circular Saw Under a Thermal Load

The optimization problem for tensioning conditions in a rotating circular saw under a thermal load is solved by a genetic algorithm. The governing equations for the in-plane behavior due to rotation, thermal load by friction, and plastic strain by tensioning and those for the resulting out-of-plane behavior are presented; the solution for in-plane forces is obtained; and a modal analysis is performed. Numerical calculations are performed to investigate the effect of tensioning conditions on the natural frequencies. The optimization problem to maximize the natural frequency of the most critical mode is solved, and the optimal tensioning conditions are determined.

Transient Thermoelastic Analysis of a Laminated Hollow Cylinder Constructed of Isotropic Elastic and Magneto-Electro-Thermoelastic Materials

This paper presents the theoretical analysis of a laminated hollow cylinder constructed of isotropic elastic and magneto- electro-thermoelastic materials under unsteady and uniform surface heating. We obtain the exact solution of the transient thermoelastic problem of the laminated hollow cylinder in the plane strain state. As an illustration, we perform numerical calculations of a three-layered composite hollow cylinder made of isotropic elastic, piezoelectric and magnetostrictive materials and investigate the numerical results for temperature change, displacement, stress, and electric and magnetic potential distributions in the transient state.

Transient Thermal Stress Problem of a Functionally Graded Magneto-Electro-Thermoelastic Hollow Sphere

This article is concerned with the theoretical analysis of the functionally graded magneto-electro-thermoelastic hollow sphere due to uniform surface heating. We analyze the transient thermoelastic problem for a functionally graded hollow sphere constructed of the spherical isotropic and linear magneto-electro-thermoelastic materials using a laminated composite mode as one of theoretical approximation in the spherically symmetric state. As an illustration, we carry out numerical calculations for a functionally graded hollow sphere constructed of piezoelectric and magnetostrictive materials and examine the behaviors in the transient state. The effects of the nonhomogeneity of material on the stresses, electric potential, and magnetic potential are investigated.