| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1993: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1992: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1991: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
Recently, various special ceramics are essential to the development of computers and many other electronic devices. When ceramic materials are subjected to a rapid change in temperature, such as thermal shock, substantial stresses develop because of temperature changes. Resistance to weakening of fracture under these conditions is called thermal endurance, thermal stress resistance, or thermal shock resistance. The effect of thermal stresses on different kinds of materials depends not only on material characteristics but also on stress level, stress distribution in the body, and stress duration. Hence, it is very important to determine the actual stress in a ceramic material under given conditions of heat transfer.
In this study we solve exactly the problem of thermal shock in structures, such as a sphere and a cylinder. When a solid sphere or cylinder is subjected to a uniform temperature rise over its cross section, stress wave occurs at the surface the moment thermal impact is applied. The stress wave at the surface proceeds radially inward to the center of the solid. The wave may accumulate at the center and give rise to very large stress magnitudes, even though the initial thermal stress is relatively small. This phenomenon is called the stress-focusing effect.
Recently Hata solved the problem of stress-focusing effects in a uniformed heated solid sphere exactly by applying the ray theory. The results show the interesting phenomenon that the stresses caused by the stress-focusing effects peak out periodically at a constant interval. This study also analyzes the effect of thermal stress waves in several solid structures precisely using the same method. The numerical results give clear indications of a stress-focusing effect. These results are useful for the design of solid structures under thermal impacts.
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