Coupled phase-field and plasticity modeling of geological materials: From brittle fracture to ductile flow

The failure behavior of geological materials depends heavily on confining pressure and strain rate. Under a relatively low confining pressure, these materials tend to fail by brittle, localized fracture, but as the confining pressure increases, they show a growing propensity for ductile, diffuse fai...

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Published in:Computer methods in applied mechanics and engineering Vol. 330; no. C; pp. 1 - 32
Main Authors: Choo, Jinhyun, Sun, WaiChing
Format: Journal Article
Language:English
Published: Amsterdam Elsevier B.V 01.03.2018
Elsevier BV
Elsevier
Subjects:
Brittle fracture
Brittle–ductile transition
Computer simulation
Confining
Crack propagation
Deformation
Ductile fracture
Ductile-brittle transition
Engineering
Failure analysis
Failure modes
Fracture
Fracture mechanics
Geology
Geomaterials
Geometry
Mathematical models
Mathematics
Mechanics
Phase field
Plastic flow
Plastic properties
Plasticity
Pressure
Propagation
Robustness (mathematics)
Strain localization
Strain rate
Studies
Fracture
Strain localization
Geomaterials
Brittle–ductile transition
Phase field
Plasticity
ISSN:0045-7825, 1879-2138
Online Access:Get full text
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Summary:The failure behavior of geological materials depends heavily on confining pressure and strain rate. Under a relatively low confining pressure, these materials tend to fail by brittle, localized fracture, but as the confining pressure increases, they show a growing propensity for ductile, diffuse failure accompanying plastic flow. Furthermore, the rate of deformation often exerts control on the brittleness. Here we develop a theoretical and computational modeling framework that encapsulates this variety of failure modes and their brittle–ductile transition. The framework couples a pressure-sensitive plasticity model with a phase-field approach to fracture which can simulate complex fracture propagation without tracking its geometry. We derive a phase-field formulation for fracture in elastic–plastic materials as a balance law of microforce, in a new way that honors the dissipative nature of the fracturing processes. For physically meaningful and numerically robust incorporation of plasticity into the phase-field model, we introduce several new ideas including the use of phase-field effective stress for plasticity, and the dilative/compactive split and rate-dependent storage of plastic work. We construct a particular class of the framework by employing a Drucker–Prager plasticity model with a compression cap, and demonstrate that the proposed framework can capture brittle fracture, ductile flow, and their transition due to confining pressure and strain rate.
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USDOE Office of Nuclear Energy (NE)
NE0008534
ISSN:0045-7825
1879-2138
DOI:10.1016/j.cma.2017.10.009