ZERODUR for stressed mirror polishing II: improved modeling of the material behavior

Ralf Jedamzik; Clemens Kunisch; Thomas Westerhoff; Ulrich Müller; Jay Daniel

doi:10.1117/12.924989

13 September 2012 ZERODUR for stressed mirror polishing II: improved modeling of the material behavior

Ralf Jedamzik, Clemens Kunisch, Thomas Westerhoff, Ulrich Müller, Jay Daniel

Proceedings Volume 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II; 84504P (2012) https://doi.org/10.1117/12.924989
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

Abstract

In the preceding part I of this paper stressed mirror polishing was stated as one of the processes assumed for the polishing of non-axisymmetric mirror blanks like those for the two ELT projects (the ESO E-ELT and the TMT). For this process it is important to have a precise knowledge of the elastic behavior of the glass ceramic mirror substrate materials. In reality glasses and glass ceramics do not react instantaneously to stresses at room temperature. This effect is called "delayed elasticity". It was shown that the delayed elasticity effect of ZERODUR^® is small in size (less than approximately 1% of the applied deformation) and fully reversible in time. A mathematical model on the relaxation of shear modulus and bulk modulus of ZERODUR^® has been introduced to predict the delayed elasticity at room temperature and different load cases. This second paper is focusing on an updated model approach with the target to improve the model prediction accuracy. The model results will be compared to measurements of the effect on a 1.5 m E-ELT mirror blank at L-3 Communications, Tinsley.

Citation Download Citation

Ralf Jedamzik, Clemens Kunisch, Thomas Westerhoff, Ulrich Müller, and Jay Daniel "ZERODUR for stressed mirror polishing II: improved modeling of the material behavior", Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 84504P (13 September 2012); https://doi.org/10.1117/12.924989

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