Thermal Stresses and Cracks During t

Thermal Stresses and Cracks During the Growth of Large-sized Sapphire with SAPMAC Method

The finite-element method has been used to study the thermal stress distribution in large-sized sapphire crystals grown with the sapphire growth technique with micro-pulling and shoulder-expanding at cooled center (SAPMAC) method. A critical defect model has been established to explain the growth and propagation of cracks during the sapphire growing process. It is demonstrated that the stress field depends on the growth rate, the ambient temperature and the crystallizing direction. High stresses always exist near the growth interfaces, at the shoulder-expanding locations, the tailing locations and the sites where the diameters undergo sharp changes. The maximum stresses always occur at the interface of seeds and crystals. Cracks often form in the critical defect region and spread in the m-planes and a-planes under applied tensile stresses during crystal growth. The experimental results have verified that with the improved system of crystal growth and well-controlled techniques, the large-sized sapphire crystals of high quality can be grown due to absence of cracks.

作 者： Xu Chenghai Meng Songhe Zhang Mingfu Zuo Hongbo Wang Guigen   作者单位： Center for Composite Structure, Harbin Institute of Technology, Harbin 150080, China  刊 名： 中国航空学报（英文版）  ISTIC 英文刊名： CHINESE JOURNAL OF AERONAUTICS  年，卷(期)： 2007 20(5)  分类号： V2  关键词： thermal stress   crack   sapphire   SAPMAC method  

【Thermal Stresses and Cracks During t】相关文章：

Chemical characteristics of aerosols at coastal station in Hong Kong.Ⅱ.Environmental behavior of trace elements during t04-26

Thermal Anomalies and Earthquakes: Evidence from Wenchuan, China04-27

Some characteristics of the atmosphere during an adiabatic process04-26

暑假英语作文：During Summer Vacation04-27

An analysis on spatial variation of urban human thermal comfort in Hangzhou,China04-26

Preliminary results on relationship between thermal diffusivity and porosity of sea ice in the Antarctic04-27

白t恤搭配09-14

什么是黄金T+D04-28

d t n l教案03-08

The retrieval of two-dimensional distribution of the earths surface aerodynamic roughness using SAR image and TM thermal04-27