Brittle-ductile failure transition in geomaterials modeled by a modified phase-field method with a varying damage-driving energy coefficient

You, Tao; Waisman, Haim; Zhu, Qi‐Zhi

doi:10.1016/j.ijplas.2020.102836

Cited by 48 publications

(18 citation statements)

References 115 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The model has been developed for the modelling of the growth of dominant cracks in homogeneous brittle materials in two-dimensions where sticking and tensile opening are not considered. Extension of the model to include these additional physical mechanisms, as well as others, such as material heterogeneity [31,32,50], tensile microcracking [31,32], pre-existing shear cracks (e.g. joints [28] or faults [31]), or different frictional shear failure criteria (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…[49]) but this work is concerned with the growth of dominant shear cracks. Most brittle materials contain pre-existing flaws/pores, which if they are small can be represented by material heterogeneity [31,32,50], or if they are large, clearly defined joints [28] or faults [31]. Again, there is no reason that these effects cannot be incorporated in to the proposed framework, but here the focus is on brittle shear failure of a homogeneous material with no pre-existing flaws, defined by the Mohr-Coulomb failure condition.…”

Section: The Damage Modelmentioning

confidence: 99%

See 1 more Smart Citation

A damage model for the frictional shear failure of brittle materials in compression

Gill¹

2021

Preprint

View full text Add to dashboard Cite

Damage models have been successfully employed for many decades in the modelling of tensile failure, where the crack surfaces separate as a crack grows. The advantage of this approach is that crack trajectories can be computed simply and efficiently on a fixed finite element mesh without explicit tracking. The development of damage models for shear failure in compression, where the crack faces slide over each other subject to friction, is a non-trivial extension of this approach. A major difference is that part of the material stiffness in the damaged region must be retained to avoid interpenetration of the crack faces. This problem is resolved here by employing an anisotropic modification to the elastic stiffness tensor in the damaged region. This has the benefit of driving frictional cracks into the correct orientation, according to the Mohr-Coulomb failure criteria, but three issues remain. The first is that the shear discontinuity introduces some spurious stress perturbations around crack regions that are narrow (less than 3-4 elements wide). This is ameliorated by Helmholtz smoothing to allow efficient simulation on a coarse mesh. The second is that the complementarity of shear stress means that the shear stiffness is removed normal to the crack interface as well as parallel to it, and the third is that there are two potentially active failure planes at each point. Both these latter two issues are resolved by the introduction of a novel failure plane selection variable, which regulates either single plane or dual plane failure, and prevents the growth of erroneous cracks normal to the crack face. Both local and non-local models are investigated for linear and exponential strain softening responses. Unlike the non-local model, the local model demonstrates some mesh-size dependence, but it still retains some properties of interest, in that it supports narrower cracks and more rapidly forms a preference for the growth of a single crack when there are a number of competing cracks. The model is implemented in commercial finite element package COMSOL Multiphysics v5.5 and validated against two benchmark simulations: biaxial compression and the failure of a 45 o slope. The correct crack angles, stipulated by the Mohr-Coulomb friction angle, are correctly reproduced, as is the postfailure residual frictional force in biaxial compression. The effect of the shear fracture energy on the force-displacement response is investigated, demonstrating the successful simulation of the range of material behaviour expected in geological samples, from broad ranged gradual collapse to sharp, almost instantaneous failure.PREPRINT: A damage model for the frictional shear failure of brittle materials in compression PREPRINT: A damage model for the frictional shear failure of brittle materials in compression they "…are computationally efficient and thus suitable for large-scale engineering simulations, phase field methods are quite demanding and therefore currently limited to small-scale problems." [47]. As such, it is an objective of ...

show abstract

Section: Discussionmentioning

confidence: 99%

Section: The Damage Modelmentioning

confidence: 99%

A damage model for the frictional shear failure of brittle materials in compression

Gill¹

2021

Preprint

View full text Add to dashboard Cite

show abstract

“…(Miehe et al, 2016;Martínez-Pañeda et al, 2020b). Other approaches have also been proposed, including a driving force for fracture based purely on the elastic stored energy (Duda et al, 2015(Duda et al, , 2018 or the consideration of elastic and plastic energies with a different weighting (see, e.g., Borden et al, 2016;You et al, 2021). A physically-sound choice is not straightforward as it is unclear to what extent a Griffith-type energy balance applies to ductile fracture (Hutchinson, 1983;Orowan, 1948).…”

Section: Hydrogen-sensitive Phase Field Damagementioning

confidence: 99%

A mechanism-based multi-trap phase field model for hydrogen assisted fracture

Isfandbod,

Martínez-Pañeda

2021

Preprint

View full text Add to dashboard Cite

We present a new mechanistic, phase field-based formulation for predicting hydrogen embrittlement. The multi-physics model developed incorporates, for the first time, a Taylor-based dislocation model to resolve the mechanics of crack tip deformation. This enables capturing the role of dislocation hardening mechanisms in elevating the tensile stress, hydrogen concentration and dislocation trap density within tens of microns ahead of the crack tip. The constitutive strain gradient plasticity model employed is coupled to a phase field formulation, to simulate the fracture process, and to a multi-trap hydrogen transport model. The analysis of stationary and propagating cracks reveals that the modelling framework presented is capable of adequately capturing the sensitivity to the hydrogen concentration, the loading rate, the material strength and the plastic length scale. In addition, model predictions are compared to experimental data of notch tensile strength versus hydrogen content on a high-strength steel; a very good agreement is attained. We define and implement both atomistic-based and phenomenological hydrogen

show abstract

“…Therefore, there is no need for a crack tracking algorithm or additional criteria for crack branching and merging. The method has found its extension in subjects such as composite failure [1,6,58], ductility [2,4,28,36,60], dynamic fracture [10,14,41,57], hydraulic fracture [11,26,54,55,61], and environment assisted failure [35,48] to name a few. When mechanics of natural materials is concerned, especially geomaterials, they often exhibit anisotropic behaviors [3,16,44].…”

Section: Introductionmentioning

confidence: 99%

Orthogonal decomposition of anisotropic constitutive models for the phase field approach to fracture

Ziaei-Rad,

Mollaali,

Nagel

et al. 2022

Preprint

View full text Add to dashboard Cite

We propose a decomposition of constitutive relations into crack-driving and persistent portions, specifically designed for materials with anisotropic/orthotropic behavior in the phase field approach to fracture to account for the tension-compression asymmetry. This decomposition follows a variational framework, satisfying the orthogonality condition for anisotropic materials. This implies that the present model can be applied to arbitrary anisotropic elastic behavior in a three-dimensional setting. On this basis, we generalize two existing models for tension-compression asymmetry in isotropic materials, namely the 'volumetric-deviatoric' model [5] and the 'no-tension' model [22], towards materials with anisotropic nature. Two benchmark problems, single notched tensile shear tests, are used to study the performance of the present model. The results can retain the anisotropic constitutive behavior and the tension-compression asymmetry in the crack response, and are qualitatively in accordance with the expected behavior for orthotropic materials. Furthermore, to study the direction of maximum energy dissipation, we modify the surface integral based energy release computation, G θ , to account only for the crack-driving energy. The computed energies with our proposed modifications predict the fracture propagation direction correctly compared with the standard G θ method.

show abstract

Brittle-ductile failure transition in geomaterials modeled by a modified phase-field method with a varying damage-driving energy coefficient

Cited by 48 publications

References 115 publications

A damage model for the frictional shear failure of brittle materials in compression

A damage model for the frictional shear failure of brittle materials in compression

A mechanism-based multi-trap phase field model for hydrogen assisted fracture

Orthogonal decomposition of anisotropic constitutive models for the phase field approach to fracture

Contact Info

Product

Resources

About