///Cyclic fatigue of annealed and tempered soda-lime glass
PhD researcher: Jonas Hilcken
Promoter: Prof. Dr. Ing. Jens Schneider
Co-promoter: Prof. Dr.-Ing. Johann-Dietrich Wörner
Chair: TU Darmstadt, Institute of Structural Mechanics and Design
Structural elements that are subjected to cyclic or repeated loading shall be classified and designed with respect to their fatigue behavior. For glass elements, no approach for the de-termination of the fatigue life has been established thus so far as the cyclic fatigue of the glass elements commonly used in construction has only been investigated rudimentarily.
In the present work, the behavior of annealed and tempered soda lime glass has been investigated performing cyclic ring-on-ring and 3-point bending tests under varying boundary conditions on samples with well-defined pre-damages. The results obtained showed that the strength of the glass is significantly reduced under cyclic loading. A threshold below which no failure occurs was found, and the main parameters responsible for cyclic fatigue were characterized and quantified. A comparison with analytical equations and a numerical model simulating the subcritical crack growth using a time-marching method have shown that the strength is reduced more substantially by cyclic loading than expected. However, the cyclic fatigue and the investigated parameters can be predicted sufficiently using common crack propagation laws with modified constants. In contrast to previous assumptions, experiments with unstressed periods between load cycles did not show a significant increase in strength, indicating no or only minor crack healing effects.
Based on the findings, a concept was developed that could be used for the design of cycli-cally loaded structural elements of annealed or tempered soda lime glass.