This book introduces theoretical and practical aspects for modelling the impact fracture of glass and laminated glass using the combined finite-discrete element method (FDEM). The FDEM is a branch of the discrete element method (DEM), and combines finite element formulation into individual discrete elements. Thus, contact forces are evaluated more accurately. Regarding the fracture of glass, a Mode I-based smeared crack model is extended and employed in the FDEM, enabling crack initiation and propagation be captured naturally. Based on the employed method and the crack model, numerical examples on fracture of glass under both hard and soft impacts are presented and validated with data from computational and experimental sources. The combined finite-discrete element method is proven to be a reliable and robust tool for examining the impact fracture responses of glass.
Contents
1. Introduction
1.1 Background
1.2 Structural Applications of Glass
1.2.1 Annealed Glass
1.2.2 Heat-Strengthened Glass
1.2.3 Toughened Glass
1.2.4 Laminated Glass
1.3 Summary
2. Brittleness and Rupture of Glass
2.1 Introduction
2.2 Theoretical Examination
2.3 Experimental Investigation
2.4 Computational Study
2.4.1 FEM
2.4.2 DEM
2.4.3 FDEM
3. Fracture Model of Glass
3.1 Overview
3.2 Smeared Crack Model
3.3 Strain Softening Curve
4. Monolithic Glass
4.1 Validation
4.2 Convergence
4.3 Parametric Study
4.3.1 Tensile Strength
4.3.2 Fracture Energy
4.3.3 Impact Velocity
4.3.4 Impact Angle
4.3.5 Projectile Size
4.4 Summary
5. Laminated Glass
5.1 FDEM Modelling
5.2 Interlayer
5.3 Glass-Interlayer Interface
5.4 Validation
5.5 Convergence
5.6 Young’s Modulus of Interlayer
5.7 Conclusions
6. Soft Impact
6.1 Introduction
6.2 Elastic Impact
6.3 Fracture Study
6.4 Comparison Study
6.4.1 Hard vs. Soft Impact
6.4.2 Laminated vs. Monolithic Glass
6.5 Parametric Study on Projectile
6.5.1 Impact Velocity
6.5.2 Young’s Modulus
6.5.3 Nose Shape
6.6 Conclusions
Research Objectives and Themes
The primary objective of this work is to investigate the impact fracture and fragmentation behavior of monolithic and laminated glass using the combined finite-discrete element method (FDEM), providing a computational tool for structural analysis to improve the safety and robustness of glass applications.
- Principles and implementation of the combined finite-discrete element method (FDEM).
- Modeling of crack initiation and propagation in brittle glass and composite laminated structures.
- Comparative analysis of hard and soft body impacts on glass structures.
- Influence of geometric and material parameters on glass breakage and fragmentation mechanisms.
- Validation of computational models against experimental data and existing literature.
Excerpt from the Book
1.2 STRUCTURAL APPLICATIONS OF GLASS
In building constructions, glass is commonly used as balconies, facades and other structural members. Roof is also popular as light can pass through it freely without any obstruction. In these cases, loads such as snow, wind and self-weight are undertaken by glass members. Broadly speaking (Ledbetter et al., 2006), the term ‘glass structures’ also includes glass elements that transfer loads other than those imposed directly on to them. Examples include beams, columns, walls, balustrades, stairs, floors, bridges, etc.
Glass beams are generally simply supported or clamped. Early examples can be found in the work of Dewhurst McFarlane (Dawson, 1995) and Nijsse (1993). A notable example is the entrance canopy to the Yuraku-cho underground station in Tokyo (Dawson, 1997) which compromises four pieces of glass bolted together. Glass columns and load-bearing walls are not common due to its brittleness as they may fail in a sudden without any pre-warning. A representative example is the 13.5m high, ground-based glass wall at the Royal Opera House, Covent Garden, London (Dodd, 1999).
Due to the aesthetic appearance and transparency, more and more challenging glass applications emerged in civil engineering within the recent decades. One of the examples is the Grand Canyon Skywalk in Arizona, US. The glass observation deck of the skywalk enables the tourists to gaze deep into the abyss without any visual barriers. Besides that, four reinforced glass ‘balconies’ were attached to the Sears Tower (now Willis Tower) for visitors. With its four 10×10 square feet compartments protruding 4.3 feet from the building’s 103rd floor observation room, the platform provides a completely transparent space to generate the sensation of hovering over Chicago, US.
Summary of Chapters
1. Introduction: Provides an overview of glass as a building material, its structural applications, and the motivation for using computational methods to study impact fracture.
2. Brittleness and Rupture of Glass: Examines the theoretical, experimental, and computational foundations of glass fracture, focusing on the limitations of traditional models.
3. Fracture Model of Glass: Introduces the fracture mechanics and cohesive zone modeling techniques implemented in the FDEM framework for predicting damage in brittle materials.
4. Monolithic Glass: Presents validation cases for monolithic glass under impact, including parametric studies on strength, energy, velocity, and projectile size.
5. Laminated Glass: Details the FDEM approach for modeling composite laminated glass, covering interlayer behavior, validation, and convergence studies.
6. Soft Impact: Explores the distinct failure mechanisms of glass structures under soft body impact compared to hard body impact, including parametric investigations on projectile properties.
Keywords
Combined Finite-Discrete Element Method (FDEM), Glass Fracture, Laminated Glass, Impact Analysis, Crack Initiation, Propagation, Fragmentation, Brittle Material, Cohesive Zone Model, Hard Impact, Soft Impact, Structural Engineering, Numerical Simulation, Finite Element Method (FEM), Discrete Element Method (DEM)
Frequently Asked Questions
What is the primary focus of this book?
The book focuses on modeling the impact fracture and fragmentation behavior of glass and laminated glass using the combined finite-discrete element method (FDEM) to assist in structural engineering and design.
What are the central thematic fields covered in the work?
The work covers material science of glass, fracture mechanics, computational numerical methods for discontinua, and dynamic analysis of structural components subjected to various impact scenarios.
What is the core research objective?
The objective is to demonstrate the applicability and accuracy of the FDEM as a robust tool for analyzing the complex breakage and fragmentation processes that occur in glass under impact.
Which scientific methodology is employed?
The study utilizes the combined finite-discrete element method (FDEM), which merges finite element formulations for element deformation with discrete element techniques for contact detection and motion.
What topics are discussed in the main chapters?
The chapters address the historical background, theoretical fracture mechanics, modeling strategies for monolithic and laminated glass, and comparative analyses of hard versus soft body impacts.
Which keywords best describe this research?
Key terms include FDEM, glass fracture, laminated glass, impact analysis, crack propagation, fragmentation, and structural safety.
How does FDEM differ from standard FEM in this study?
While FEM excels in continuum problems, it struggles with discrete modeling and fragmentation; FDEM overcomes this by allowing individual elements to separate and interact, providing a more realistic representation of crack propagation.
What specific role does the interlayer play in laminated glass performance?
The interlayer acts as a bonding medium that holds fragments together after fracture, thereby significantly enhancing the energy absorption capacity and reducing the hazard posed by sharp glass shards.
What is the significance of the "soft impact" analysis?
Soft impact analysis is critical for automotive safety and debris protection, as it accounts for the extensive deformation of the projectile, which significantly alters the load duration and fracture mechanisms compared to rigid hard-body impacts.
- Quote paper
- Xudong Chen (Author), 2019, Impact Fracture of Glass. The Combined Finite-Discrete Element Study, Munich, GRIN Verlag, https://www.grin.com/document/505219
