Significance of K-dominance zone size and nonsingular stress field in brittle fracture

Kumar, Bhawesh; Chitsiriphanit, Suvanit; Sun, C. T.

doi:10.1016/j.engfracmech.2011.03.015

Cited by 36 publications

(11 citation statements)

References 16 publications

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“…While the non-singular stresses may not have a direct contribution on the value of K I , they can indirectly influence its magnitude. [13] In order to estimate K I from the numerical results we used the projection method as presented in [32] and briefly described below. Considering the y-direction normal stress distribution (σ θθ ) ahead of the crack tip (θ=0) only, equation (1) can be transformed as:…”

Section: Analysis Of Numerical Resultsmentioning

confidence: 99%

“…The K-dominant region was considered as the zone around the crack tip where K I contributes to more than 95% of the opening stress at the crack tip (see horizontal dashed line in Figure 3b). The degree of K-dominance [13,15,33] is therefore estimated as:…”

Section: Analytical Interaction Integralmentioning

confidence: 99%

“…This assumption, however, is limited and can often produce unrealistic results. For example, even for the same material, specimens of different configurations can exhibit apparently different fracture toughness values which can be more accurately predicted by taking into account additional crack tip parameters [10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

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K-dominance and size effect in mode I fracture of brittle materials with low to medium porosity

Touliatou

Wheel

2018

Engineering Fracture Mechanics

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Linear Elastic Fracture Mechanics usually only considers the singular stresses when describing the conditions under which fracture would occur in a brittle material. However, it is becoming more widely recognised that non-singular stresses can become significant depending on the geometry and configuration of the specimen. This study investigates the impact of non-singular stresses on the stress intensity of low to medium porosity brittle materials. To address this, discrete finite element models of Double Cantilever Beam (DCB) samples were created and the full near-tip stress field in mode I loading was numerically evaluated. A parametric study was conducted, examining the influence of overall specimen size, material porosity and crack tip location relative to the nearest void. Results indicate a prominent size effect on the stress intensity at the crack tip of porous materials, with smaller specimen exhibiting tougher behaviour than their respective larger counterparts. This size effect, which is amplified with increasing porosity, is closely correlated with the variation of non-singular stresses, both parallel and normal to the crack plane. A model to predict the behaviour of porous specimen for different sizes is suggested based on the findings.

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Section: Analysis Of Numerical Resultsmentioning

confidence: 99%

Section: Analytical Interaction Integralmentioning

confidence: 99%

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K-dominance and size effect in mode I fracture of brittle materials with low to medium porosity

Touliatou

Wheel

2018

Engineering Fracture Mechanics

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“…In this case the fracture load is expected to be different from the specimens with lower constraint effect. It has been shown in previous researches that different fracture toughness values can be obtained for an identical material when using various specimens' geometries [1][2][3][4][5][6][7][8][9]. This paper shall show differences between the well-known one-parameter fracture mechanics concept and the multiparameter one.…”

Section: Introductionmentioning

confidence: 82%

Crack propagation in a brittle DCB specimen assessed by means of the Williams’ power expansion

Berto

Ravazi

Malíková

2019

Frattura Ed Integrità Strutturale

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A double cantilever beam geometry has been chosen in order to investigate the importance of the higher-order terms of the Williams' power expansion for the crack path estimation. The crack propagation has been tested experimentally on a brittle polymethylmethacrylate (PMMA) specimen and although the mode I loading conditions were applied, the crack kinked from its original plane immediately and propagated towards the bottom side of the specimen. It has been shown that this phenomenon is connected to the magnitude and sign of the T-stress and to the level of the constraint generally. In this work, the influence of the third and higher terms of the Williams' series on the crack propagation is investigated. The generalized form of the well-known maximum tangential stress fracture criterion for determination of the crack propagation angle has been tested and discussed. The observed differences in the crack trajectory of different specimens have been found to be related to the magnitude of the higher-order terms of the stress tensor components at the crack tip.

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“…Experiments on brittle materials are mainly focused on homogeneous specimens. However, even for this presumably predictable case, different values of fracture toughness have been reported for different specimen configurations or sizes, deviating from the usual scaling predicted by LEFM [12][13][14][15][16]. In order to explain such discrepancies, scientists are rejecting the notion of an indisputably large K-dominant zone and are investigating two parameter models, including non-singular terms in addition to the SIF, to more accurately and consistently predict the fracture toughness of different specimens.…”

Section: Introductionmentioning

confidence: 98%

Experimental and numerical analysis of size effects on stress intensity in anisotropic porous materials

Touliatou

Wheel

2019

Engineering Failure Analysis

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A prominent size effect has previously been reported for the fracture behaviour of brittle porous materials, with smaller specimens behaving quite differently to their larger counterparts. In such materials, the size of the K-dominant zone has been numerically found to be greatly affected by the presence of voids in the near-tip area, thus putting the assumption of a single fracture parameter under question. In order to address this, in this study mode I tests are conducted on porous double cantilever beam specimens, while the stress distribution in the near-tip area is being observed by means of photoelasticity. Results validate the predicted size effect and suggest that the voids can indeed alter the size and shape of the stress pattern in the specimens. A parametric study is then conducted to investigate the influence of void shape variations that can be caused by manufacturing inaccuracies on the stress concentration at the crack tip. It is found that although the stress intensity at the crack tip can be greatly affected by such factors, the size of the K-dominant zone remains unaffected.

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Significance of K-dominance zone size and nonsingular stress field in brittle fracture

Cited by 36 publications

References 16 publications

K-dominance and size effect in mode I fracture of brittle materials with low to medium porosity

K-dominance and size effect in mode I fracture of brittle materials with low to medium porosity

Crack propagation in a brittle DCB specimen assessed by means of the Williams’ power expansion

Experimental and numerical analysis of size effects on stress intensity in anisotropic porous materials

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