Low temperature inelasticises of silica-glasses

Dr.-Ing. Frank Schneider, OKALUX GmbH

The behaviour of glass at room temperature was investigated. A delayed elastic deformation and a load-depending stiffness could be verified experimentally and explained theoretically by a simple model.

A static loading was applied and the deflection was measured during a six month loading period and a subsequent recovery phase. An increasing delayed elastic deformation of ~2 % was measured for thermally toughened soda-lime-silica glass,
which was found to be mostly reversible. No change of material parameters such as Young’s modulus, light-transparency or tensionalstrength could be identified. Glasses
of different chemical composition were investigated in a second step to confirm the results and identify the responsible mechanism. For fused silica no time depending behaviour could be found. Hence, a slow diffusion of the network-modifying cations was
identified to be the most possible reason for the retardation process. Another inelastic effect could also be verified. Depending on the applied load level the Young’s modulus of the glass varies. The stiffness increases exponential with the loading, reaching asymptotically its acknowledged value. A structural model, based on statistical considerations and diffusion processes of mobile cations has been developed to describe both fundamental mechanism qualitatively.

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The Authors

Dr. Frank Schneider Research and Development Director OKALUX GmbH 1993 – 1999 • Studies: Darmstadt University of Technology, Darmstadt, Germany • Title of qualification awarded: Diploma in Civil Engineering 2000 – 2005 • Name and address of employer: Darmstad... Read more