How to get a correct estimate of the plastic zone size for shear-mode fatigue cracks?

Vojtek, Tomáš; Hrstka, Miroslav

doi:10.1016/j.tafmec.2019.102332

Cited by 10 publications

(2 citation statements)

References 29 publications

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“…But note that when real experimental mixed-mode displacement fields are analysed, due to friction stresses that reduce ∆K ef f II , the effective size of the mode II plastic zone is not known a priori, and is often actually significantly smaller than predicted, inserting the nominal K II in eq. 2 [28].…”

Section: Methodsmentioning

confidence: 99%

Determination of effective stress intensity factors under mixed‐mode from digital image correlation fields in presence of contact stresses and plasticity

Bonniot

Doquet

Hai

2019

Strain

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Digital Image Correlation (DIC) is more and more popular to monitor fatigue crack growth and to determine the stress intensity factors. However, the post-treatment of the recorded displacement fields becomes tricky when the crack faces are not stress-free and when crack tip plasticity becomes significant. Several post-treatment methods to locate the crack tip and measure the effective SIFs in such cases are compared, using FEM-computed displacement fields, and then used on real DIC fields. An approach coupling DIC and FEM is proposed to estimate the contact stresses along the crack.

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Section: Methodsmentioning

confidence: 99%

Determination of effective stress intensity factors under mixed‐mode from digital image correlation fields in presence of contact stresses and plasticity

Bonniot

Doquet

Hai

2019

Strain

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“…Several research [23,24,25,26] are focused on the determination of the plastic zone but the notion of the fracture process zone is rarely developed [17]. In this paper, the plastic zone found by the Irwin's model and the fracture elaboration zone assumed by the volumetric approach will be studied and compared using the formula proposed at the base of the Irwin's model.…”

Section: Introductionmentioning

confidence: 99%

Plastic zone size at notch tip in mode I fracture using the modified Irwin’s model and volumetric approach

Fakir¹,

Minor²

2021

MATEC Web Conf.

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At crack tip the stress distribution has singularities (i.e the stress intensity is infinite) which is physically impossible. Irwin realised that the stresses at crack tip are finite and subsequently introduced the Stress Intensify Factor(SIF). This factor is used to determine this plastic zone size. The crack is a special case of the notch. Around the notch, the fracture needs a volume to develop according to the volumetric approach. This volume is characterised by the distance effective Xeff, the stress effective σeff and the stress intensity factorKρI. In This paper a new proposed formula called “Modified Irwin’s Model” based on Irwin’s model can be used to determine the plastic zone size. This new formula will be verified using numerical finite element simulation and validated using the Von-Mises and Tresca Criteria. The Modified Irwin’s Model can be an alternative way to estimate the fracture elaboration zone from the plastic zone.

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Misconception of the Use of 2D Plane Stress Solutions for Free Surfaces of Cracked Bodies and Its Significance for Full Field Measurement Techniques

Vojtek,

Kubíček,

Pokorný

et al. 2024

Adv Eng Mater

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Although 2D fracture mechanics solutions have been successfully applied, many analyses are affected by the wrong presumption of the 2D plane stress state at the free surface intersected by a crack front. The significance of this presumption and the related confusion have grown rapidly with the progress of strain field measurement techniques, such as the digital image correlation. The article demonstrates this wrong presumption on two of the most commonly measured and studied entities, which are the plastic zone in front of the crack tip and the crack tip opening displacement. 3D stress and strain solution is necessary to be performed. A realistic crack front curvature is required to be considered. Only such solutions can be used for comparison with the experimentally obtained strain fields. Other solutions are wrong and can bring confusion, wrong conclusions about material behavior, and slow down the progress in the field of fracture mechanics due to the incompatibility of the presumed stress state and the stress state present in experiments.

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How to get a correct estimate of the plastic zone size for shear-mode fatigue cracks?

Cited by 10 publications

References 29 publications

Determination of effective stress intensity factors under mixed‐mode from digital image correlation fields in presence of contact stresses and plasticity

Determination of effective stress intensity factors under mixed‐mode from digital image correlation fields in presence of contact stresses and plasticity

Plastic zone size at notch tip in mode I fracture using the modified Irwin’s model and volumetric approach

Misconception of the Use of 2D Plane Stress Solutions for Free Surfaces of Cracked Bodies and Its Significance for Full Field Measurement Techniques

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