A new approach to characterisation of the fracture behaviour of solid materials
File(s)
Author(s)
Ho, Dac Duc
Type
Thesis
Abstract
The key to characterising the fracture response of heterogenous solid materials lies in the knowledge of their microstructures, which remains limited as it is difficult to obtain reliable information for the microstructures that contain random microheterogeneities like grains, inclusions, microvoids, microcracks, and defects. In this study, we describe the material microstructure using two different approaches: the deterministic approach and the stochastic approach. The deterministic approach employs the representative volume element (RVE) [1] to provide a spatial uniform distribution of mechanical properties while the stochastic approach adopts the statistical volume element (SVE) [2] to introduce random fields of mechanical properties in the material domain. Idealised finite element (FE) models are developed to physically represent specific test specimens while simple analytical models are introduced to serve as first-order approximations of the FE models. The models are defined using specific local constitutive laws that allow them to represent a generic isotropic, ductile solid. First, we investigate the sensitivity of the solid’s fracture response, characterised by tensile strength, fracture toughness, and ductility, to relevant features of the local constitutive laws, and explore the dependence of the fracture response on the degree of heterogeneity. Then, the relation among tensile strength, fracture toughness, and ductility is established to develop a new framework for characterising the fracture response of heterogenous solids. Finally, we propose various deterministic and stochastic modelling strategies to predict the mechanical response of a sintered Ti material. Different aspects of the mechanical response are considered, ranging from the undamaged response that is associated to elasticity and plasticity to the damaged response that is associated to tensile strength, stiffness degradation, fracture toughness, and crack propagation. A scoring system is introduced to systematically evaluate the performance of the strategies and the most effective strategy is determined.
Version
Open Access
Date Issued
2025-03-30
Date Awarded
2026-03-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Tagarielli, Vito
Publisher Department
Department of Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)