Abstract

Phase-field models of fracture allow the prediction of crack propagation and crack patterns. In this contribution, externally driven fracture processes in linear and finite elasticity are investigated. Different approaches to consider pneumatic pressure and materials with non-isotropic crack resistance are studied, combined, and examined in detail. The versatility of the proposed models is proven by a series of numerical simulations in two and three dimensions.

Highlights

  • The prediction of crack growth and fracture patterns is a central topic of fracture mechanics

  • Various studies have been made on external load driven fracture, in particular, on hydraulic fracturing where a fluid under high pressure is injected into compressed soil to open cracks

  • In this work we present a model for pneumatic fracture in solids with non-isotropic fracture resistance

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Summary

Introduction

The prediction of crack growth and fracture patterns is a central topic of fracture mechanics. Ghamgosar et al (2015) suggest to introduce various critical fracture energy densities GcI , GcI I , GcI I I for each rock direction This technique was used in the early phase-field models of Adda-Bedia et al (1999) to capture the preferred direction of crack propagation. In the last years it has been generalized to a Griffith energy tensor or, alternatively, a structural tensor included in the regularized variational phase-field formulation, cf Clayton and Knap (2015), Teichtmeister et al (2017), Liu and Juhre (2018) and Li et al (2015) Such a tensor weights the partial derivatives in different directions separately. Numerical simulations for pressure induced crack growth in materials with layer-wise fracture resistance are presented in Sect.

The phase-field approach to fracture
Finite elasticity
Linear elasticity
Pneumatic fracture
Pressure driven crack growth
Proof of concept
Validation
Two notch crack propagation
Crack propagation with a Rankine stress model
Phase-field model with non-isotropic crack resistance
Random variations in tensile resistance
Deterministic conductance tensor
Mode-I tension test with different weights
Mode-II shear test with different weights and crack driving forces
Mode-I tension test with different directions
Randomly weighted direction dependence
Numerical Examples
Pressure driven crack growth in plane stress
Pressure driven crack growth in a cylinder with centered crack
Concluding remarks
Full Text
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