Optical anisotropy effects in tempered glass can affect the transparency of glass building envelopes in the form of iridescence. Birefringence is created in the standard tempering process and results from even the smallest principal stress differences across the thickness of the glass. Currently, no standard or guideline exists for evaluating optical anisotropy effects in tempered glass. In recent years, photoelastic methods have been developed for full-field, non-destructive measurement of optical retardation caused by anisotropy effects. This study focuses on whether and how the retardation measurements correlate with the visual anisotropy effects under natural daylight in reality. Therefore, quantitative retardation measurements were first performed on various glass panes, followed by qualitative studies to correlate the visibility of the anisotropy effects in an outdoor test facility. The investigation shows that the quantitative measurement of optical retardation and the presented evaluation methods allow the objective evaluation of anisotropy effects.
The relation between measurement and visibility of anisotropy effects in tempered glass. A case study.
Company: Institute for Material and Building Research, University of Applied Science, Munich
About the speaker:
Steffen Dix started his career with an apprenticeship as a technical draftsman at seele GmbH. He holds an MEng in civil engineering focusing on steel, lightweight and glass construction at the University of Applied Sciences in Munich.
Since the beginning of his study, he worked in the laboratory for steel and light metal construction (LSL). First as a working student, under Ömer Bucak, until today as a Research Assistant under Christian Schuler. Since 2016, his research has focused on quality control of tempered glass, resulting in his nearly finished Ph.D. thesis, ” A Concept for Measuring and Evaluating Optical Anisotropy Effects in Tempered Architectural Glass”.