Numerical modelling of fatigue crack closure and its implication on crack front curvature using CTODp

0570509 - ÚFM 2024 RIV GB eng J - Journal Article
Oplt, Tomáš - Vojtek, Tomáš - Kubíček, Radek - Pokorný, Pavel - Hutař, Pavel
Numerical modelling of fatigue crack closure and its implication on crack front curvature using CTODp.
International Journal of Fatigue. Roč. 171, JUN (2023), č. článku 107570. ISSN 0142-1123. E-ISSN 1879-3452
R&D Projects: GA ČR(CZ) GA22-28283S
Institutional support: RVO:68081723
Keywords : Crack closure * Crack front curvature * ctod * Finite element modelling * Steel
OECD category: Materials engineering
Impact factor: 6, year: 2022
Method of publishing: Limited access
https://www.sciencedirect.com/science/article/pii/S0142112323000713?via%3Dihub

One of the widely used approaches to characterize fatigue crack propagation is the use of the effective stress intensity factor range ΔKeff, which relies on determination of crack closure value Kcl. The used models of crack closure are most frequently-two-dimensional, however, for real cracks, the 3D effects should be taken into account. The paper presents 3D finite element analyses of the influences of crack front shape, inserted cycles (loading cycles between node releases) and crack closure on the crack driving force in terms of ΔKeff and ΔCTODp (plastic part of crack tip opening displacement range). Numerically obtained crack closure depended on the simulation strategy. In the case of inserted cycles, crack closure disappeared in the internal part of the specimen and remained only near the free edges. The use of ΔCTODp had the advantage of a well-defined parameter in situations where ΔKeff was problematic, namely at the corner points, which did not allow finding of equalized crack driving force along the whole crack front using ΔKeff. Equalized crack driving force in terms of ΔCTODp was found for crack front curvature with the edge angle 15.4° in simulation with crack closure, which was in good agreement with the experimentally measured value of 16°. Loops produced by loading and unloading branches of the force vs CTOD diagrams helped to describe the crack closure process and magnitude. Actual values of CTOD did not agree with the classical idea of 2D solutions under plane strain and plane stress. CTOD was larger in the internal part of the specimen than at the free edges, even in simulations with no crack face contact.
Permanent Link: https://hdl.handle.net/11104/0341806