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26 July 1999 High-temperature compression and ring-on-ring testing of sapphire
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Sapphire's strength at elevated temperature is highly dependent on the test conditions. Tests that involve compressive forces at localized contact point can cause failure strengths due to the rhombohedral twinning. High contact stress can result at the load points due to roughness of surfaces. A thin sheet of Grafoil serves as a complaint layer between the load surface and the specimen and reduces the contact stress, and this increased the compression strength by a factor of 4 and the biaxial flexure of c oriented specimens by 2X at 600 degrees C. The strength reported by different testing facilities was comparable when Grafoil was used. The use of Grafoil has made it possible to evalute the effect of process parameters on the compressive and biaxial flexure strength at 600 degrees C.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Frederick Schmid, Keil A. Schmid, Chandra P. Khattak, and Daniel C. Harris "High-temperature compression and ring-on-ring testing of sapphire", Proc. SPIE 3705, Window and Dome Technologies and Materials VI, (26 July 1999);


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