On the Fracture Behaviour and the Fracture Pattern Morphology of Tempered Soda-Lime Glass

verfasst von: Navid Pour-Moghaddam

Verlag: Springer Fachmedien Wiesbaden

Buchreihe : Mechanik, Werkstoffe und Konstruktion im Bauwesen

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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Über dieses Buch

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.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract

In recent decades, the use of glass as a construction element of the structural glazing and as a building material in various engineering sectors such as the automotive sector, the shipping industry and solar technology has increased significantly. This fact has substantially increased the demand for structural and architectural flexibility and versatility of glass components. Glass components are applied as architectural and structural elements in buildings, see Figure 1.1. However, glass is a brittle material with a linear elastic material behaviour at room temperature until fracture and lacks the capability of stressredistribution in contrast to more common building materials.

Navid Pour-Moghaddam

Chapter 2. Glass Properties and Refinement Processes

Abstract

Glass is an amorphous solid that is usually produced by a melting process. Thermodynamically, glass is called to be the frozen state of a supercooled liquid (SCHOLZE, 1988). If a liquid is cooled down below its melting point T_m, crystallisation usually takes place because the crystalline state is energetically more favourable than the liquid (SCHNEIDER et al., 2016). However, it takes some time for the molecules to build up a crystalline solid to reach the most favourable energetic position in the crystal lattice.

Navid Pour-Moghaddam

Chapter 3. Numerical Simulation of the Thermal Tempering Process

Abstract

Thermal tempering of glass is a heat treatment process. During quenching, the cooling rate, i.e. the rate of temperature change, governs and affects thermal strains and mechanical behaviour. The tempering process is affected by heat transfer and glass support. The theory of heat transfer is covered in many books dealing with the basic concepts of conduction, convection and radiation, see e.g. BEJAN (1993) and MILLS (1999). The heat transfer during the thermal tempering process is described in Section 3.2.

Navid Pour-Moghaddam

Chapter 4. Experimental Investigations into the Fragmentation of Tempered Glass

Abstract

Glass is one of the most popular building materials today. However, the tensile strength is governed by small flaws that significantly reduce the actual engineering strength of annealed float glass, see e.g. SCHULA (2015), HILCKEN (2015) or SCHNEIDER et al. (2016). Thermally tempered glass shows a higher resistance to external loads due to its residual stress state and, in case of failure, is quite safe with regard to cutting and stitching due to the small, blurred fragments. For this reason, thermally tempered glass is also referred to as safety glass.

Navid Pour-Moghaddam

Chapter 5. Prediction of 2D Macro-Scale Fragmentation of Tempered Glass

Abstract

The fracture behaviour of glass concerns scientists all over the world since decades. As glass is considered a brittle material, the strength of glass is typically described by the Linear Elastic Fracture Mechanics (LEFM). First pioneering work within fracture mechanics of glass was conducted by Griffith in 1920 (Griffith, 1921). Since then numerous authors have contributed to analysing the fracture structure of glass.

Navid Pour-Moghaddam

Chapter 6. Investigations into the Phenomenon of Crack Branching

Abstract

A particularly peculiar phenomenon in fracture mechanics is bifurcation or crack branching, which occurs when a crack runs rapidly under high stress intensity. Bifurcation also occurs with a crack under simple tensile stress, which initially propagates perpendicularly to the tensile stress that has been applied to the crack. Various criteria have been proposed for specifying branching conditions in brittle materials.

Navid Pour-Moghaddam

Chapter 7. Summary and Outlook

Abstract

This thesis offered comprehensive analysis of the fracture behaviour and significant characteristics of the fracture pattern morphology of fragmented thermally tempered sodalime- silica glass. Investigations on influencing parameters and variables of the fracture process as well as the fracture mechanical properties and the physical quantities of the fracture pattern morphology were provided. Fragmentation analyses to determine correlations between the residual stress and the morphological properties of the fracture pattern of soda-lime-silica glass were carried out due to fracture tests on differently heat treated glass specimens of different thickness.

Navid Pour-Moghaddam

Backmatter

Titel: On the Fracture Behaviour and the Fracture Pattern Morphology of Tempered Soda-Lime Glass
verfasst von: Navid Pour-Moghaddam
Verlag: Springer Fachmedien Wiesbaden
Electronic ISBN: 978-3-658-28206-6
Print ISBN: 978-3-658-28205-9
DOI: https://doi.org/10.1007/978-3-658-28206-6