Evaluation of the surface strength of glass plates shaped by hot slumping process

• Published in: Optical engineering 2014-08, Vol.53 (8), p.085101-085101
• Main Authors: Proserpio, Laura, Basso, Stefano, Borsa, Francesco, Citterio, Oberto, Civitani, Marta, Ghigo, Mauro, Pareschi, Giovanni, Salmaso, Bianca, Sironi, Giorgia, Spiga, Daniele, Tagliaferri, Gianpiero, D'Este, Alberto, Dall'Igna, Roberto, Silvestri, Mirko, Parodi, Giancarlo, Martelli, Francesco, Bavdaz, Marcos, Wille, Eric
• Format: Article
• Language: English
• Subjects: Glass; Mathematical models; Optical data processing; Plates; Slumping; Strength; Telescope design; X-rays
• ISSN: 0091-3286; 1560-2303
• DOI: 10.1117/1.OE.53.8.085101

Hot slumping technology is under development by several research groups in the world for the realization of grazing-incidence segmented mirrors for x-ray astronomy, based on thin glass plates shaped over a mold at temperatures above the transformation point. The performed thermal cycle and related operations might have effects on the strength of the glass, with consequences for the structural design of the elemental optical modules and, consequently, on the entire x-ray optic for large astronomical missions such as IXO and ATHENA. The mechanical strength of glass plates after they underwent the slumping process was tested through destructive double-ring tests in the context of a study performed by the Astronomical Observatory of Brera with the collaboration of Stazione Sperimentale del Vetro and BCV Progetti. The entire study was done on more than 200 D263 Schott borosilicate glass specimens of dimensions 100  mm×100  mm and a thickness 0.4 mm, either flat or bent at a radius of curvature of 1000 mm through the pressure-assisted hot slumping process developed by INAF-OAB. The collected experimental data have been compared with nonlinear finite element model analyses and treated with the Weibull statistic to assess the current IXO glass x-ray telescope design, in terms of survival probability, when subjected to static and acoustic loads characteristic of the launch phase. The paper describes the activities performed and presents the obtained results.