Masayuki Ishihara

Piezothermoelastic analysis of a cross-ply laminate considering the effects of transverse shear and coupling

In this study, we treat the behavior of a piezothermoelastic composite plate taking into account the effects of transverse shear and coupling among mechanical, thermal, and electrostatic fields. As an analytical model, we consider a rectangular laminate composed of several fiber-reinforced laminae and a piezoelectric layer. All the laminae are assumed to exhibit 2-mm symmetry and the principal axes of anisotropy to coincide with coordinate axes, that is, a cross-ply laminate is considered. We assume that the laminate is subjected to mechanical, thermal, and electrical loads with all edges simply supported and treat the problem as a coupled piezothermoelastic one. Numerical calculation is carried out to examine the effects of transverse shear and coupling on the behavior of the laminate. Moreover, the control of the deflection by applied voltage is examined.

Analysis of Dynamic Characteristics of Rotating Circular Saw Subjected to Thermal Loading and Tensioning

An analysis is carried out to investigate the dynamic characteristics of a tensioned circular saw. The analytical model is a rotating annular disc, undergoing plastic strain at a given temperature. By using the plate bending theory, the governing equations for the in-plane behavior during rotation and under thermal load and plastic strain and those for the resulting out-of-plane behavior are derived. Then, the solution of in-plane forces is obtained and the modal analysis is carried out. The in-plane forces and natural frequencies are calculated numerically to investigate the effect of tensioning conditions on them, and to find suitable tensioning conditions.

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.

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.

Analytical technique for thermoelectroelastic field in piezoelectric bodies with D∞ symmetry in cylindrical coordinates

ABSTRACT A general solution technique for non-axisymmetric thermoelectroelastic problems in cylindrical domains with D∞ symmetry is constructed. The displacement and electric field are expressed in terms of the respective potential functions, and the thermoelectroelastic field quantities are expressed in terms of the elastic and piezoelastic potential functions, each of which essentially satisfies a Laplace equation with respect to the spatial coordinates, combined with the two thermoelastic displacement potential functions. As an application of the technique, the theoretical analysis of a solid cylinder subjected to combined mechanical and thermal loading is performed, and the necessity of the thermoelectroelastic analyses is demonstrated.

General Solution Technique for Electroelastic Problems in Green Materials

In view of the engineering significance of piezoelectric bodies with D ∞ symmetry, such as bulk wood and film or fibers made of poly-L-lactic acid, an analytical technique is constructed for general solutions to electroelastic problems in these bodies. First, the constitutive equations which describe the symmetry are presented. 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 three functions, namely an elastic displacement potential functions and two piezoelastic displacement potential functions, and the former is found to satisfy a fourth-order differential equation and the latter to satisfy a Laplace equation with respect to the appropriately transformed spatial coordinates.

504 Transient Thermoelasticity of a Laminated Composite Hollow Sphere with an Interlayer of Functionally Graded Materials

Functionally graded materials (FGMs) are inhomogeneous materials, in which the properties vary continuously from one surface to the other. Typically, these materials are made from a mixture of ceramic and metal. The characteristics of ceramic yield the high-temperature resistance due to their excellent and thermal property, but have a serious defect such as brittleness. The characteristics of metal, on the other hand, prevent fracture caused by stresses due to their mechanical strength. FGMs are the material which can have both properties. In the future, we expect that FGMs are used in the various engineering applications. A functionally graded interlayer can reduce the thermal stresses caused by the material constant mismatch between a ceramic and a metal. And it is well-known that the thermal stress distributions in a transient state can show large value compared with the one in a steady state. Then, the analytical studies concerned with transient thermoelasticity become important. The transient thermoelastic problems of laminated composite strip and laminated hollow cylinder with an interlayer of functionally graded material were analyzed exactly [1,2]. In this paper, we analyze the transient thermoelastic problem for a laminated composite hollow sphere with an interlayer of functionally graded material, and obtain the exact solution for the one-dimensional temperature change and thermoelastic response. 2. Analysis