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9 February 2019 Minimum lifetime of ZERODUR® structures based on the breakage stress threshold model: a review
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Abstract
Increasing demand for using the glass ceramic ZERODUR® for optical elements with high mechanical loads called for strength data based on statistical samples larger than 20 specimens. The data now available for a variety of practical surface conditions (ground, lapped, and etched) allow stresses by factors 4 to 10 times higher than before. The larger samples revealed that breakage stresses of ground surfaces follow the three-parameter Weibull distribution. The threshold parameter of this distribution reflects the existence of an upper limit for the microcracks depth within such surfaces. It is equivalent to a minimum strength below which breakage probability is zero. Its use in the well-established crack growth theory allows calculating minimum lifetimes including fatigue using the stress corrosion constant for the prevailing environmental humidity. Long-term loading tests have confirmed the validity of the model. For fully etched surfaces, the Weibull statistics fails because in such cases failure mechanism is not unique anymore. Nevertheless, ZERODUR® with fully etched surfaces that are free from other damages still exhibit minimum breakage stress above 100-MPa tensile stress. The successful satellite mission LISA Pathfinder has confirmed the possibility to apply ZERODUR® for utmost precision experiments together with high mechanical loads.
CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
Peter Hartmann "Minimum lifetime of ZERODUR® structures based on the breakage stress threshold model: a review," Optical Engineering 58(2), 020902 (9 February 2019). https://doi.org/10.1117/1.OE.58.2.020902
Received: 24 October 2018; Accepted: 14 January 2019; Published: 9 February 2019
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CITATIONS
Cited by 9 scholarly publications.
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KEYWORDS
Zerodur

Glasses

Etching

Surface finishing

Failure analysis

Corrosion

Diamond

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