Size effects on brittle fracture of Brazilian disk samples containing a circular hole

Two nonlocal approaches are applied to the borehole geometry, herein simply modelled as a circular hole in an infinite elastic medium, subjected to remote biaxial loading and/or internal pressure. The former approach lies within the framework of Gradient Elasticity (GE). Its characteristic is nonlocal in the elastic material behaviour and local in the failure criterion, hence simply related to the stress concentration factor. The latter approach is the Finite Fracture Mechanics (FFM), a well-consolidated model within the framework of brittle fracture. Its characteristic is local in the elastic material behaviour and non-local in the fracture criterion, since crack onset occurs when two (stress and energy) conditions in front of the stress concentration point are simultaneously met. Although the two approaches have a completely different origin, they present some similarities, both involving a characteristic length. Notably, they lead to almost identical critical load predictions as far as the two internal lengths are properly related. A comparison with experimental data available in the literature is also provided.

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“…Let us now provide the solution by means of FFM, inspired by some previous works [31][32][33].…”

Section: Finite Fracture Mechanicsmentioning

confidence: 99%

Non-local criteria for the borehole problem: Gradient Elasticity versus Finite Fracture Mechanics

2021

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“…Results show that only when the diameter of the Brazilian disc is at least 20 times the ball radius can the dispersion of the results be eliminated, but the effects of the contact normal bond strength on the Brazilian tensile strength were ignored. Torabi et al [22] and Yang et al [23] examined the theoretical value and the measured value of stress distribution in a circular ring from the perspective of fracture mechanics, revealing that the maximum tensile strength of a single-hole disc decreased with the increasing ball radius ratio. However, they neglected the effect of the contact normal bond strength on the maximum tensile strength.…”

Section: State Of the Artmentioning

confidence: 99%

Effects of Contact Normal Bond Strength on Brazilian Tensile Strength by Particle Flow Code

Huang¹,

Fu²,

Miao³

et al. 2020

JESTR

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The Contact Bond Model (CBM) of Particle Flow Code (PFC) can effectively simulate the mechanical behaviours of rocks. The physical and mechanical parameters of CBM directly influence the results of the numerical simulation of rocks. To reveal the influence mechanism of the contact normal bond strength of the CBM on Brazilian tensile strength, this study proposes a numerical test model and calculation method for the Brazilian tensile strength. First, the theoretical relationship between the Brazilian tensile strength and the contact normal bond strength of the CBM was derived. Second, 70 groups (350) of PFC Brazilian disk numerical tests were designed, and a numerical model of the Brazilian tensile strength was established. Third, the effects of the contact normal bond strength on the Brazilian tensile strength under various ball radii and ball radius ratios were analyzed according to the PFC numerical simulation results, and the correctness of the theoretical relation was verified. Results demonstrate that the Brazilian tensile strength is significantly and linearly related to the contact normal bond strength and can be expressed as the product of the contact normal bond strength and the scale coefficient. The scale coefficient is affected by the geometric parameters of balls. The scale coefficient generally increases with the minimum particle size, whereas the change in the coefficient becomes irregular. Results reveal the physical significance of the PFC normal bond strength to a certain extent. The proposed method can determine the contact normal bond strength.

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“…Leguillon et al [ 45 ] predicted the onset of crack growth in RV notches and voids (cavities) considering the influence of the specimen size by using the finite fracture mechanics (FFM) theory. Furthermore, the effect of notch size has been assessed in some studies such as those published by Torabi et al [ 46 ] and Negro et al [ 47 , 48 ].…”

Section: Introductionmentioning

confidence: 99%

A Modified Mean Stress Criterion for Considering Size Effects on Mode I Fracture Estimation of Rounded-Tip V-Notched Polymeric Specimens

et al. 2022

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The aim of this paper is to assess the size and geometry effects on the mode I notch fracture toughness of polymeric samples containing rounded-tip V-shaped (RV) notches (V-notch with a finite radius at the notch tip). First, using a large number of fracture tests on an RV-notched Brazilian disk and semi-circular bending polymeric samples with four different sizes, the size-dependent values of the notch fracture toughness are obtained. Then, the mean stress criterion is modified for characterizing the size-dependency of notch fracture toughness in polymeric samples. The resulting modified mean stress criterion considers higher order terms of the stress field when calculating the fracture process zone length around the tip of the defect. Additionally, the critical distance rc is assumed to be associated with the specimen size and a formula containing fitting parameters is utilized for considering this trend of rc. The comparison between the values of notch fracture toughness obtained from experiments and those predicted by the modified mean stress criterion shows that the suggested approach can provide accurate estimations of size-dependent values of notch fracture toughness in polymeric specimens containing RV notches.

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Size effects on brittle fracture of Brazilian disk samples containing a circular hole

Cited by 45 publications

References 42 publications

Non-local criteria for the borehole problem: Gradient Elasticity versus Finite Fracture Mechanics

Non-local criteria for the borehole problem: Gradient Elasticity versus Finite Fracture Mechanics

Effects of Contact Normal Bond Strength on Brazilian Tensile Strength by Particle Flow Code

A Modified Mean Stress Criterion for Considering Size Effects on Mode I Fracture Estimation of Rounded-Tip V-Notched Polymeric Specimens

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