Ryuusuke Kawamura

TRANSIENT HEAT CONDUCTION AND THERMAL STRESS PROBLEMS OF A NONHOMOGENEOUS PLATE WITH TEMPERATURE-DEPENDENT MATERIAL PROPERTIES

Nonhomogeneous materials, such as functionally gradient materials (FGM), have special characteristics due to arbitrarily distributed and continuously varied material properties. For such nonhomogeneous materials, the heat conduction equation is presented in a nonlinear form. In this paper, the temperature solution for such a nonlinear system is formulated approximately, and the solution of the integral form of nonuniform thermal material constants is given. Taking into account the effect of temperature dependency of material properties, the one-dimensional transient heat conduction problem of such a nonhomogeneous plate is analyzed theoretically, and the associated thermal stress distribution is formulated under the mechanical of traction-free condition. Numerical calculations are carried out for a nonhomogeneous plate made of Zirconium Oxide and Titanium alloy. The influence of a temperature dependency in material properties and of a change of nonhomogeneity affected by the temperature and the thermal st...

THERMAL BENDING OF LAMINATED COMPOSITE RECTANGULAR PLATES AND NONHOMOGENEOUS PLATES DUE TO PARTIAL HEATING

This article is concerned with a thermal bending analysis of a laminated composite rectangular plate due to a partially distributed heat supply. For the theoretical development, we have introduced the methods of finite cosine transformation and Laplace transformation to the temperature field and adapted the classical plate theory based on Kirchhoff-Loves hypothesis to the thermoeiastic field. Thereafter, we have applied the theoretical development proposed in the present article to the analysis of a nonhomogeneous rectangular plate of the thermal stress relaxation type such as functionally gradient material. Then we have evaluated temperature change, thermal stress, and thermal deflection of simply supported plates and clamped ones. And we have examined the effect of relaxation on distributions of the thermal stress and thermal deflection for the nonhomogeneous rectangular plate.

Optimization of material composition of nonhomogeneous hollow sphere for thermal stress relaxation making use of neural network

In this study, a neural network is applied to optimization problems of material compositions for a nonhomogeneous hollow sphere with arbitrarily distributed and continuously varied material properties such as functionally graded material (FGM). Using the analytical procedure of a laminated hollow sphere model, the analytical temperature solution for the nonhomogeneous hollow sphere is derived approximately. Furthermore, the thermal stress components are formulated under the mechanical condition of being traction free. As a numerical example, the nonhomogeneous hollow sphere composed of zirconium oxide and titanium alloy is considered. Also, as the optimization problem of minimizing the thermal stress distribution, the numerical calculations are carried out making use of neural network, and the optimum material composition is determined taking into account the effect of temperature-dependency of material properties. Furthermore, the results obtained by neural network and ordinary nonlinear programming method are compared.

THEORETICAL ANALYSIS OF THERMOELASTOPLASTIC DEFORMATION OF A CIRCULAR PLATE DUE TO A PARTIALLY DISTRIBUTED HEAT SUPPLY

In this article, we consider a circular plate and discuss the transient thermoelastoplastic bending problems making use of the strain increment theorem. In order to develop the analysis for the temperature field, we introduce the methods of generalized finite Fourier transform and finite Hankel transform. And for the theoretical analysis of thermoelastoplastic deformation of the plate, we treat the problem as plate bending, which is usually applied to the analysis of thermoelastic deformation. For the thermoelastic deformation, the analytical solution is obtained. On the other hand, for the plastic deformation, the solution is evaluated with the aid of the finite difference method. For the numerical calculations, the strain increment is calculated by successive elastic solution. Some numerical results are shown graphically.

THERMAL BUCKLING ANALYSIS OF INHOMOGENEOUS RECTANGULAR PLATE DUE TO UNIFORM HEAT SUPPLY

This paper is concerned with the thermal buckling analysis of an isotropic inhomogeneous rectangular plate subjected to the arbitrary thermal loads. The fundamental equations system is derived by introducing the technique of the newly defined position of the reference plane, which allows us to analyze the problem using an elementary plate theory. It is assumed that the material properties such as the coefficient of linear thermal expansion α, the thermal conductivity λ, and Youngs modulus of elasticity, E, are changed in the thickness direction with the power law of the coordinate variable, whereas Poissons ratio ν is assumed to be constant. As an illustrative example, we consider the thermal buckling problem of a simply supported inhomogeneous rectangular plate due to uniform heat supply. Numerical calculations are carried out for several cases taking into account the variations of the inhomogeneous material properties, aspect ratio, and width-to-thickness ratio.

OPTIMIZATION OF MATERIAL COMPOSITION OF NONHOMOGENEOUS HOLLOW CIRCULAR CYLINDER FOR THERMAL STRESS RELAXATION MAKING USE OF NEURAL NETWORK

In this study, a neural network is applied to optimization problems of material compositions for a nonhomogeneous hollow circular cylinder with arbitrarily distributed and continuously varied material properties such as those of a functionally graded material. Using the analytical procedure of a laminated hollow circular cylinder model, the analytical temperature solution for the cylinder is derived approximately. Further more, the thermal stress components are formulated under the mechanical condition as being traction-free and making use of the Airys stress function method. As a numerical example, the hollow circular cylinder composed of zirconium oxide and titanium alloy is considered. In addition, for the optimization problem of minimizing the thermal stress distribution, the numerical calculations are made using a neural network and the optimum material composition is determined taking into account the effect of the temperature dependency of material properties. Furthermore, the results obtained by ...

Magneto-Thermo-Elastic Stresses Induced by a Transient Magnetic Field in a Conducting Hollow Circular Cylinder

We investigate the dynamic and quasi-static behavior of magneto-thermo-elastic stresses induced by a transient magnetic field in a conducting hollow circular cylinder. A transient magnetic field defined by an arbitrary function of time acts on the outer surface of the hollow cylinder and parallel to it. The fundamental equations of plane axisymmetrical electromagnetic, temperature and elastic fields are formulated, and solutions for the magnetic field, eddy current, temperature change and dynamic and quasi-static solutions for stresses and deformations are analytically derived in terms of the arbitrary function. The stress solutions are determined to be sums of a thermal stress component caused by eddy current loss and a magnetic stress component caused by the Lorentz force. The case of a magnetic field defined by a smoothed ramp function with a sine-function profile is examined in particular, and the dynamic and quasi-static behavior of the stresses and deformations are numerically calculated.

Thermally Induced Vibration of Inhomogeneous Material Rectangular Plate Due to Cyclic Variation of Thermal and Mechanical Loads

The purpose of this study is to clarify thermally induced vibration of a thin‐walled rectangular plate with inhomogeneous material properties in a thickness direction due to cyclic variation of thermal and mechanical loads. An effect of inhomogeneity of material properties on thermoelastic responses due to thermal and mechanical loadings is examined. When frequencies in loadings are close to natural frequency of the plate, vibrations due to both loadings offset each other. It is found that an effect of variation of natural frequency due to inhomogeneities in Youngs modulus or mass density on dynamic response is more significant than that of variation of thermal resultant moment due to inhomogeneity in coefficient of linear thermal expansion.

Thermally Induced Vibration of an Inhomogeneous Beam due to a Cyclic Heating

With the improvement of the performance and the efficiency of machines, the use of thin-walled and lightweight structural members has been frequently required in machines operating in high temperatures and under high internal pressure. An application of inhomogeneous materials, such as functionally graded materials, in structures subjected to the extremely high temperatures has been anticipated and development of such materials is being actively continued. In general, it often happens that the thermally induced instability, such as vibration and buckling, creates problems in the thin-walled and lightweight structural members, leading to the reduction of stiffness.

Dynamic and Quasi-Static Behaviors of Magneto-Thermo-Elastic Stresses in a Conducting Solid Circular Cylinder Subjected to an Arbitrary Variation of Magnetic Field

In the present article, dynamic and quasi-static behaviors of magneto-thermo-elastic stresses in a conducting solid circular cylinder subjected to an arbitrary variation of magnetic field are investigated. It is assumed that a magnetic field defined by an arbitrary function of time acts on the surface in the direction parallel to its surface. Dynamic and quasi-static solutions of stresses are analytically derived. The solutions of stresses are determined to be sums of thermal stress caused by eddy current loss and magnetic stress caused by Lorentz force. For the case that the arbitrary function is given by the sine function, the dynamic and quasi-static behaviors of the stresses are examined by numerical calculations.