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Proceedings Paper

Delayed elasticity in Zerodur at room temperature
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Paper Abstract

Much has been written about structural relaxation, viscous flow, delayed elasticity, hysteresis, and other dimensional stability phenomena of glass and ceramics at elevated temperatures. Less has been documented about similar effects at room temperature. The time dependent phenomenon of delayed elasticity exhibited by Zerodur has been studied at room temperature and is presented here. Using a high-performance mechanical profilometer, a delayed strain on the order of 1 percent is realized over a period of a few weeks, under low stress levels. An independent test using optical interferometry validates the results. A comparison of Corning ULE silica glass is also made. The effect is believed to be related to the alkali oxide content of the glass ceramic and rearrangement of the ion groups within the structure during stress. The effect, apparent under externally applied load, is elastic and repeatable, that is, no hysteresis of permanent set, as measured at elevated temperature, is evidenced within measurement capabilities. Nonetheless, it must be accounted for in determining the magnitude of distortion under load (delayed elastic creep) and upon load removal (delayed elastic recovery). This is particularly important for large lightweight optics which might undergo large strain during fabrication and environmental loading, such as experienced in gravity release or in dynamic control of active optics.

Paper Details

Date Published: 1 December 1991
PDF: 10 pages
Proc. SPIE 1533, Optomechanics and Dimensional Stability, (1 December 1991); doi: 10.1117/12.48857
Show Author Affiliations
John W. Pepi, Itek Optical Systems (United States)
Donald Golini, Itek Optical Systems (United States)

Published in SPIE Proceedings Vol. 1533:
Optomechanics and Dimensional Stability
Roger A. Paquin; Daniel Vukobratovich, Editor(s)

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