Notch effect on the fracture of several rocks: Application of the Theory of Critical Distances

Justo, Juan B.; Castro, José Villaverde; Cicero, Sergio; Sánchez-Carro, M.A.; Husillos, R.

doi:10.1016/j.tafmec.2017.05.025

Cited by 52 publications

(57 citation statements)

References 18 publications

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“…This means that the notch radius apparently does not affect the mechanism of crack initiation in EAC. This result is in contradiction with the observations made in the analysis of ordinary fracture processes …”

Section: Resultscontrasting

confidence: 99%

“…This result is in contradiction with the observations made in the analysis of ordinary fracture processes. 8,16,17 The displacement rate and the applied current density, which significantly affect the K N IEAC , have an almost imperceptible influence on the failure mechanisms. However, the lower the displacement rate (6•10 −9 m/s), the more brittle the fracture surfaces become with a larger concentration of cleavages.…”

Section: Sem Analysismentioning

confidence: 99%

“…The simplest and at the same time most relevant methodology is the point method (PM) since it has been successfully applied in fracture and fatigue analyses. 5 Numerous researchers [6][7][8] have proved the accuracy of the TCD when carrying out fracture and fatigue assessments. However, the TCD has not yet been employed in environmentally assisted cracking (EAC) analyses.…”

Section: Introductionmentioning

confidence: 99%

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Prediction of crack propagation thresholds in notched steels subjected to environmentally assisted cracking: An approach from the theory of critical distances

Gutiérrez

Cicero

Arroyo

et al. 2019

Mat Design & Process Comms

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This article presents the analysis of environmentally assisted cracking (EAC) processes in two steels containing U-shaped notches through the point method (PM). This methodology belongs to the theory of critical distances (TCD) and has been widely validated in fracture and fatigue analysis in many materials. However, it has never been used in EAC process assessment. The resulting methodology is validated by testing C(T) notched specimens of X80 and S420 steels subjected to aggressive environments under hydrogen embrittlement conditions. The parameters of the TCD have been obtained by finite element simulations, and the results reveal that the PM accurately predicts the crack propagation onset condition (K N IEAC), as well as the evolution of the apparent EAC crack propagation threshold of the material. The study has been completed with an exhaustive analysis of the fracture surfaces to determine the failure mechanisms using scanning electron microscopy (SEM).

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Section: Resultscontrasting

confidence: 99%

Section: Sem Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prediction of crack propagation thresholds in notched steels subjected to environmentally assisted cracking: An approach from the theory of critical distances

Gutiérrez

Cicero

Arroyo

et al. 2019

Mat Design & Process Comms

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“…For this reason, trying to fill this knowledge gap, this paper focuses on the use of the SED criterion for the fracture prediction of six different rocks containing U-shaped notches and with notch radii varying from 0.15 mm to 15 mm. To this end, the study is based on the results of a systematic laboratory campaign performed by the authors of this article in [29,30], which successfully applied the Theory of the Critical Distances for the fracture assessment of those six rocks. With all this, Section 2 provides an overview of the SED criterion, particularising the expressions to the geometry and conditions studied in this paper.…”

Section: Introductionmentioning

confidence: 99%

Energy-based approach for fracture assessment of several rocks containing U-shaped notches through the application of the SED criterion

Justo

Castro

Cicero

2018

International Journal of Rock Mechanics and Mining Sciences

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This work presents an energetic continuum approach for the fracture assessment of rocks containing U-shaped notches and subjected to Mode I loading conditions. Three different methodologies are proposed in this article, all of them based on the premise that brittle failure will occur when the average strain energy density over a certain control area reaches a critical value that only depends on the material, as stated by the Strain Energy Density (SED) criterion.The first method proposed (A) deals with the application of the SED criterion through an expression with a series of already tabulated parameters, which are particularised for the analysed rocks by rational extrapolation. Therefore, this first method avoids the use of numerical analysis. By contrast, the second method (B) aims to obtain numerically the previously extrapolated parameters, and the third method (C) directly relates the strain energy density with the applied load, without the use of those parameters.The research is based on the results obtained from an exhaustive experimental programme comprising 300 fracture specimens tested in four-point bending conditions. These tests combine parallelepiped samples made of 6 different types of rocks (two marbles, two limestones, a sandstone and a granite) and containing 8 different notch radii (varying from 0.15 mm up to 15 mm).Thus, this work aims to show the potential, capacity and limitations of the SED criterion in rock fracture analyses, comparing with this purpose the experimentally obtained fracture loads and those predicted by the three proposed methodologies.

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“…This parameter is often used as a criterion for predicating fracture initiation which is fundamentally important in understanding the mechanical properties of rocks. Although fracture toughness is often considered as an intrinsic property of a rock material, it still can vary with many factors including geological anisotropy [3,4], geometrical properties of the laboratory-scale specimens [5][6][7], temperature [8], and loading conditions [9,10]. As such, a comprehensive description of the possible variation of fracture toughness arising from those factors is of great importance for a better understanding of the mechanical behaviour of anisotropic rocks, as well as for a proper selection of pressure and viscosity of liquid used for fracturing anisotropic rocks.…”

Section: Introductionmentioning

confidence: 99%

Broad-spectrum fracture toughness of an anisotropic sandstone under mixed-mode loading

Shang

Gui

Zhao

2018

Theoretical and Applied Fracture Mechanics

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Fracture toughness of anisotropic rocks can vary with many factors such as geological anisotropy, geometrical properties of specimens used in the laboratory (e.g., pre-existing crack properties), and loading conditions. This fact has been widely acknowledged. Yet the variation in fracture toughness remains enigmatic, as there is still lack of a comprehensive study on how those influential factors affect fracture toughness behavior of anisotropic rocks.The present paper shows a broad-spectrum mixed-mode fracture toughness of an anisotropic sandstone from a numerical scheme, which is based on the Discrete Element Method (DEM). In this study, a total of 340 semi-circular bend (SCB) specimens with various geological and geometrical conditions were numerically prepared by systemically varying the orientations of planar anisotropy (i.e. incipient bedding plane), as well as the magnitudes of the ISRM-suggested geometrical parameters of the SCB specimens (i.e. crack length, crack angle, and span length). The numerical model used in the study was calibrated against a series of laboratory experiments to select proper micro-parameters to reproduce the mechanical characteristics of anisotropic Midgley Grit sandstone (MGS). Additionally, four different fracture criteria, which are based on stress and strain analysis, and the analysis of energy density, were used to predict the mixed-mode fracture behaviour of MGS.Numerical findings from this study were compared with experimental observations (qualitatively) and theoretical predictions (quantitatively). A broad agreement was observed in the comparison study. Highlights Broad-spectrum mixed-mode fracture toughness of an anisotropic sandstone based on a total of 340 DEM simulations. Influences of crack length and angle, span length, as well as geological anisotropy on fracture behaviour. Comparisons between results obtained from DEM simulations, laboratory experiments and theoretical analysis.

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Notch effect on the fracture of several rocks: Application of the Theory of Critical Distances

Cited by 52 publications

References 18 publications

Prediction of crack propagation thresholds in notched steels subjected to environmentally assisted cracking: An approach from the theory of critical distances

Prediction of crack propagation thresholds in notched steels subjected to environmentally assisted cracking: An approach from the theory of critical distances

Energy-based approach for fracture assessment of several rocks containing U-shaped notches through the application of the SED criterion

Broad-spectrum fracture toughness of an anisotropic sandstone under mixed-mode loading

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