EVALUATION OF THERMAL STRESSES INDUCED IN ANISOTROPIC MATERIAL DURING THERMAL SHOCK

In machines and structures operating in a high-temperature environment, such as a turbine blade or a cutting tool, repeated thermal shock is known to induce damage and fracture. Such damages are big problems in technical fields. In developing a good material with a high resistance to thermal shock, it is essential to conduct a quantitative evaluation of the thermal stresses induced in the material during the thermal shock. However, until recently, there have been few methods to evaluate the thermal stresses quantitatively at a given instant of the thermal shock. As an experimental method for the quench-type thermal shock, the present authors proposed the new method that enables us to evaluate the thermal stresses quantitatively. Using this method, we succeeded in clarifying the characteristics of thermal shock of several materials, such as ceramics, cemented carbide, and cermets. However, the influence of the material anisotropy on the thermal stresses induced by the thermal shock is still unknown. In the present study, we perform the thermal shock experiment using two kinds of materials with different degrees of the material anisotropy. From the experiment, it is clarified that the thermal stresses induced by the thermal shock vary with the material anisotropy. A similar result was also obtained using the finite element method (FEM) simulation, which covers a wide range of the material anisotropy. A simple expression was found via simulations used to evaluate the thermal stresses when the material has anisotropies in physical properties, such as Young's modulus and a linear expansion coefficient.