On The Fracture Behaviour And The Fracture Pattern Morphology Of Tempered Soda Lime Glass
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On the Fracture Behaviour and the Fracture Pattern Morphology of Tempered Soda-Lime Glass
Author: Navid Pour-Moghaddam
language: en
Publisher: Springer Nature
Release Date: 2019-11-08
The main criteria for assessing the load-bearing behaviour and risk potential of monolithic glass are its fragmentation and the morphology of the fragments. These depend strongly non-linearly on the strain energy density present in the glass at the time of fracture, which can be converted into fracture energy. Thus, the design and optimization of structural glazing in engineering requires both knowledge of the relevant parameters and mechanisms during the fracture process in glass and an understanding of the characteristics of the fracture structure. Based on fracture mechanics considerations and comprehensive experimental investigations, various aspects and physical quantities of fracture behaviour as well as characteristics and parameters of fracture pattern morphology of fragmented, tempered soda-lime glass were studied and correlated with the stored strain energy. The relationship between fragmentation behavior and strain energy was elaborated using the energy criterion in Linear Elastic Fracture Mechanics (LEFM) related to the initial strain energy before fragmentation and in the post-fracture state. Furthermore, a machine learning inspired approach for the prediction of 2D macro-scale fragmentation of tempered glass was developed and elaborated based on fracture mechanics considerations and statistical analysis of the fracture pattern morphology. A method was deduced and applied in which the fracture pattern of tempered glass is predicted and simulated by Voronoi tessellation of point patterns based on Bayesian spatial point statistics fed with energy conditions in LEFM.
A Concept for Measuring and Evaluating Optical Anisotropy Effects in Tempered Architectural Glass
Optical anisotropy effects can occur in building envelopes made of tempered glass. The visual effect has been neglected in the evaluation of the building product and increasingly leads to disputes between the parties involved. This thesis extends the state of knowledge on the cause and perception of optical anisotropic effects and presents a concept for measuring and evaluating them in flat monolithic tempered architectural glass. Initially, an overview and description of current photoelastic measurement methods are given, and the accuracy of the used measurement setups is verified for the first time. The experimental basis for the concept is formed by extensive full-field retardation measurements in the laboratory and field studies of the maximum visibility of the anisotropy effects in an outdoor test rig with accompanying polarization measurements of the sky. Various glass types, geometries, and tempering levels are selected based on typically used products, and their influence on the resulting retardation image is investigated. Determining a correlation of the retardation images with the reflection images of selected test specimens in the outdoor test rig complements the experiments. Based on this, digital evaluation methods are presented, further developed, and applied to the measured retardation images. From the critical analysis of these results, limit values for different anisotropy quality classes are derived, and the concept is complemented. With the implementation of the evaluation methods and the limit values in commercial anisotropy scanners, the quality of each glass pane can be determined directly after tempering in the future. By choosing the highest quality class A, it will be possible in the future to significantly reduce anisotropy effects in constructions made of tempered glass panes.
Characterization of Laminated Safety Glass Interlayers
Laminated safety glass enables the safe construction of transparent structures. The mechanical behaviour depends on the polymeric interlayer both in the intact and in the post fracture state. In the present work, the mechanical behaviour of ethylene vinyl acetate-based (EVA) and ionoplastic interlayers is investigated for the intact laminated safety glass condition. In particular, the influence of the semi-crystalline structure on the stiffness behaviour is studied with X-Ray Diffraction, Differential Scanning Calorimetry and Dynamic-Mechanical-Thermal-Analysis. The studies on the mechanical behaviour of the interlayer in the fractured laminated safety glass were carried out with polyvinyl butyral-based (PVB) interlayers. First, the temperature and frequency (time) dependent linearity limits are determined in Dynamic-Mechanical-Thermal-Analyses, second, the nonlinear viscoelastic material behaviour is investigated with tensile relaxation tests at different temperatures and strain levels.