Elastic Twinning and Cleavage Fracture in Calcite Crystals: Experimental Methods and Preliminary Results

Report No. ARL-TR-6144
Authors: Corydon D. Hilton; Jian H. Yu; Jeffrey J. Swab
Date/Pages: September 2012; 28 pages
Abstract: Twinning and cleavage fracture are fundamental deformation mechanisms which occur in crystalline solids. Calcite has been considered an ideal material for experimental deformation twinning studies for many years due to its transparency and the fact that slip does not occur in the material at room temperature. Although it has been acknowledged that elastic twinning can be induced in calcite materials by indenting upon the cleavage face of the crystal, there is a lack of quantitative data on twin growth behavior for twins created in this manner. Additionally, the historical calcite twinning literature lacks high-quality images of elastic twins. The major focus of the experimental work presented here is on elastic twins created by indenting the (100) cleavage face of natural calcite crystals. High-quality images of the twin growth process are presented along with initial quantitative results (including twin length as a function of indentation load and indentation load-displacement data). In addition, preliminary results are included for cleavage fracture experiments performed on calcite materials.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2012