Theoretical Development of Optimization Problem of Material Composition and Evaluation of Thermal Stress Intensity Factor for Heat-Resisting Functionally Graded Materials

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In this research project, thermal stress problems for nonhomogeneous materials such as the Functionally Graded Materials are treated theoretically for several analytical models. The FGMs are composed of the light metals and the engineering ceramics, and now attracts our engineering attention by the effect of thermally induced stress relaxation. Then, the following two practical problems are dealt with theoretically in the present research project.1. Optimization problems of material composition for nonhomogeneous body to minimize thermal stresses under the condition of unsteady heatingIn this research, taking into account the several analytical model, such as a plate, a cylindrical shell and spherical shell composed of nonhomogeneous materials, the optimization problems of material composition to minimize the transient thermal stress distributions are treated theoretically. And the optimum material composition are determined from the nonlinear programming method of calculations. And th … More e variations of several numerical parameter, such as temperature-dependency of material properities, temperature rise, thickness and the conditions of heat transfer, affected to the optimum material composition are examined from the numerical data of calculation.2. Evaluation of thermal stress intensity factor for nonhomogeneous bodyIn this research, theoretical development of thermal stress intensity factor for nonhomogeneous body is treated theoretically. As an analytical model, Kassir' s nonhomogeneous infinite body with a pennyshaped crack is considered. Assuming that the body is subjected to uniform heat flox from the crack surface, and the material properties such as thermal conductivity, shear modulus of elasticity and coefficient of linear thermal expansions vary with the axial direction according to the relation of power product form of the coordinate variable, the thermal stress intensity factor is evaluated theoretically. And the effects of variation of these material properities to the stress intensity factor are examined from the numerical data. Less