A crack closure model of fatigue crack growth in plates of finite thickness under small-scale yielding conditions

Codrington, John; Kotousov, Andrei

doi:10.1016/j.mechmat.2008.10.002

Cited by 71 publications

(43 citation statements)

References 33 publications

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“…It seems that all fracture toughening mechanisms may not be fully activated at the micro-scale. These mechanisms may include roughness or plasticity induced closure, which cannot be developed in micro-samples due to the limited crack growth increments [57]. This study was only limited to acicular ferrite as the main purpose was to demonstrate the possible miniaturisation of IHAC fracture testing at the scale of individual microstructural constituents.…”

Section: Resultsmentioning

confidence: 99%

Investigation of hydrogen assisted cracking in acicular ferrite using site-specific micro-fracture tests

Costin

Lavigne

Kotousov

et al. 2016

Materials Science and Engineering: A

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Hydrogen assisted cracking (HAC) is a common type of failure mechanism that can affect a wide range of metals and alloys. Experimental studies of HAC are cumbersome due to various intrinsic and extrinsic parameters and factors (associated with stress, hydrogen and the materials microstructure) contributing to the hydrogen crack kinetics. The microstructure of many materials consists of diverse constituents with characteristic features and mechanical properties which only occur in very small material volumes. The only way to differentiate the effect of these individual constituents on the hydrogen crack kinetics is to miniaturise the testing procedures. In this paper we present a new experimental approach to investigate hydrogen assisted crack growth in a microstructural constituent, i.e. acicular ferrite. For this purpose, sharply notched microcantilevers were fabricated with a Focus Ion Beam within this selected microscopic region. Acicular ferrite can be found in many ferrous alloys including ferritic weld metal and has specific features that control its intrinsic susceptibility to HAC. These features were characterised via Electron Backscatter Diffraction and the specimens were subsequently loaded under uncharged and hydrogen charged conditions with a nanoindenter. The outcomes of the testing, demonstrated that the threshold stress intensity factor, Kth, to initiate crack propagation in acicular ferrite ranges between 1.56 MPa m1/2 and 4.36 MPa m1/2. This range is significantly below the values of Kth reported for various ferrous alloys in standard macro-tests. This finding indicates that the mechanisms and resistance to HAC at micro-scale could be very different than at the macroscale as not all fracture toughening mechanisms may be activated at this scale level. Hydrogen assisted cracking (HAC) is a common type of failure mechanism that can affect a wide range of metals and alloys. Experimental studies of HAC are cumbersome due to various intrinsic and extrinsic parameters and factors (associated with stress, hydrogen and the materials microstructure) contributing to the hydrogen crack kinetics. The microstructure of many materials consists of diverse constituents with characteristic features and mechanical properties which only occur in very small material volumes. The only way to differentiate the effect of these individual constituents on the hydrogen crack kinetics is to miniaturise the testing procedures. In this paper we present a new experimental approach to investigate hydrogen assisted crack growth in a microstructural constituent, i.e. acicular ferrite. For this purpose, sharply notched micro-cantilevers were fabricated with a Focus Ion Beam within this selected microscopic region. Acicular ferrite can be found in many ferrous alloys including ferritic weld metal and has specific features that control its intrinsic susceptibility to HAC. These features were characterised via Electron Backscatter Diffraction and the specimens were subsequently loaded under uncharged and hydrogen charged con...

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Section: Resultsmentioning

confidence: 99%

Investigation of hydrogen assisted cracking in acicular ferrite using site-specific micro-fracture tests

Costin

Lavigne

Kotousov

et al. 2016

Materials Science and Engineering: A

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“…Many models have been developed in the past [14,15]. Below we present an analytical model [16], which directly incorporates the plate thickness and will be used in conjunction with parametric finite element calculations as outlined above.…”

Section: Analytical Approachmentioning

confidence: 99%

“…when η → ∞ or η → 0, respectively. The details of the derivation of these equations can be found in the original paper by Codrington and Kotousov [16].…”

Section: Analytical Approachmentioning

confidence: 99%

Evaluation of Fatigue Crack Front Shape for a Specimen with Finite Thickness

Kotousov

Branco

2015

MATEC Web of Conferences

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Abstract. Two-dimensional elastic or elasto-plastic models dominate the current fatigue crack growth assessment and life prediction procedures for plate components with through-the-thickness cracks. However, as demonstrated in many theoretical and experimental papers, the stress field near the crack tip is always three-dimensional and the fatigue crack front is not straight. In this paper, we develop a simplified approach for the evaluation of the front shapes of through-the-thickness fatigue cracks. We validate this approach against experimental results available from published papers.

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“…A three-dimensional model for the evaluation of the residual strength of two collinear cracks of equal length was developed in [12] based on the strip yield model [5,6] and the plasticity induced crack closure concept [13][14]. In [12], the crack problem was formulated using the distributed dislocation technique, i.e.…”

Section: Theoretical Approachmentioning

confidence: 99%

Experimental Study on Local Plastic Collapse in a Plate Weakened by Two Collinear Cracks

Mohabuth

Chang

Khanna

2015

MATEC Web of Conferences

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Abstract. Fracture and fatigue assessment of structures weakened by multiple site damage (MSD) currently represents a challenging problem. Here, we communicate the outcomes of an experimental study conducted on a plate weakened by two closely-spaced collinear cracks, which represents the simplest form of MSD. The experimental results are used to verify the predictions of a recently developed theoretical approach.

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A crack closure model of fatigue crack growth in plates of finite thickness under small-scale yielding conditions

Cited by 71 publications

References 33 publications

Investigation of hydrogen assisted cracking in acicular ferrite using site-specific micro-fracture tests

Investigation of hydrogen assisted cracking in acicular ferrite using site-specific micro-fracture tests

Evaluation of Fatigue Crack Front Shape for a Specimen with Finite Thickness

Experimental Study on Local Plastic Collapse in a Plate Weakened by Two Collinear Cracks

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