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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Vydané v:	Computer methods in applied mechanics and engineering Ročník 330; číslo C; s. 1 - 32
Hlavní autori:	Choo, Jinhyun, Sun, WaiChing
Médium:	Journal Article
Jazyk:	English
Vydavateľské údaje:	Amsterdam Elsevier B.V 01.03.2018 Elsevier BV Elsevier
Predmet:	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
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Shrnutí:	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.
Bibliografia:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 USDOE Office of Nuclear Energy (NE) NE0008534
ISSN:	0045-7825 1879-2138
DOI:	10.1016/j.cma.2017.10.009