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Crack Opening Profiles of Indentation Cracks in Normal and Anomalous Glasses

Published

Author(s)

Z Burghard, A Zimmermann, J Rodel, F Aldinger, Brian R. Lawn

Abstract

A comparative Vickers indentation study is made of two glasses, soda-lime andborosilicate. Indentations in the two glasses reveal substantially shorter radial cracks in the borosilicate, even though toughness values measured by conventional (doublecantilever beam) methods are similar in the two glasses. Here, indentation toughness is measured in two ways: by optical measurement of the indentation crack lengths (ICL); and by AFM measurement of crack-opening displacements in the near-crack-tip regions(COD). The ICL measurements indicate artificially high values for the borosilicaterelative to the soda-lime, consistent with previously documented indentation results. The COD measurements indicate similar values for the two glasses, in line withexpectations from the independent determinations. In the case of soda-lime glass, the COD and ICL values are mutually consistent. In the case of borosilicate, the COD and ICL values differ widely, indicating anomalous indentation behavior, typical of glasses with open, network-former structures. It is concluded that the COD route provides more reliable evaluations of intrinsic toughness, albeit at some expense in experimental simplicity. Residual elastic plastic contact stresses responsible for driving the radial cracks, deconvoluted from COD measurements over the entire radial crack lengths, are shown to be significantly smaller in the borosilicate relative to soda-lime, indicative of a compaction rather than volume-conserving contact deformation mode.
Citation
Acta Materialia
Volume
52
Issue
No. 2

Keywords

anomalous glass, crack-opening displacement, indentation toughness, residual stress

Citation

Burghard, Z. , Zimmermann, A. , Rodel, J. , Aldinger, F. and Lawn, B. (2004), Crack Opening Profiles of Indentation Cracks in Normal and Anomalous Glasses, Acta Materialia (Accessed May 18, 2024)

Issues

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Created December 31, 2003, Updated October 12, 2021