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Proceedings Paper

ZERODUR: bending strength data for etched surfaces
Author(s): Peter Hartmann; Antoine Leys; Antoine Carré; Franca Kerz; Thomas Westerhoff
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Paper Abstract

In a continuous effort since 2007 a considerable amount of new data and information has been gathered on the bending strength of the extremely low thermal expansion glass ceramic ZERODUR®. By fitting a three parameter Weibull distribution to the data it could be shown that for homogenously ground surfaces minimum breakage stresses exist lying much higher than the previously applied design limits. In order to achieve even higher allowable stress values diamond grain ground surfaces have been acid etched, a procedure widely accepted as strength increasing measure. If surfaces are etched taking off layers with thickness which are comparable to the maximum micro crack depth of the preceding grinding process they also show statistical distributions compatible with a three parameter Weibull distribution. SCHOTT has performed additional measurement series with etch solutions with variable composition testing the applicability of this distribution and the possibility to achieve further increase of the minimum breakage stress. For long term loading applications strength change with time and environmental media are important. The parameter needed for prediction calculations which is combining these influences is the stress corrosion constant. Results from the past differ significantly from each other. On the basis of new investigations better information will be provided for choosing the best value for the given application conditions.

Paper Details

Date Published: 18 July 2014
PDF: 9 pages
Proc. SPIE 9151, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation, 91512Q (18 July 2014); doi: 10.1117/12.2055801
Show Author Affiliations
Peter Hartmann, SCHOTT AG (Germany)
Antoine Leys, SCHOTT AG (Germany)
Antoine Carré, SCHOTT AG (Germany)
Franca Kerz, SCHOTT AG (Germany)
Thomas Westerhoff, SCHOTT AG (Germany)

Published in SPIE Proceedings Vol. 9151:
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation
Ramón Navarro; Colin R. Cunningham; Allison A. Barto, Editor(s)

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