Fatigue crack growth modelling based on CTOD for the 7050‐T6 alloy

Antunes, F.V.; Branco, R.; Prates, Pedro A.; Borrego, L.P.

doi:10.1111/ffe.12582

Cited by 52 publications

(26 citation statements)

References 77 publications

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“…Therefore, cyclic loading was applied to smooth specimens in order to obtain stress-strain response, which was subsequently used to fit the material constants. The capability of analyzing crack closure and fatigue crack growth using CTOD was fully demonstrated in an earlier work by the authors [15].…”

Section: Fcg Analysis Based On Plastic Ctod Rangementioning

confidence: 93%

Fatigue Crack Growth in Maraging Steel Obtained by Selective Laser Melting

et al. 2019

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Selective Laser Melting (SLM) is an additive manufacturing technology, ideal for the production of complex-shaped components. Design against fatigue is fundamental in the presence of cyclic loads, particularly for these materials which typically have significant porosity, high surface roughness and residual stresses. The main objective here is to study fatigue crack growth (FCG) in the 18Ni300 steel obtained by SLM. Typical da/dN-ΔK curves were obtained in C(T) specimens, indicating that cyclic plastic deformation may be the controlling mechanism. A complementary analysis, based on plastic CTOD range, showed a relatively low level of crack tip plastic deformation, and consequently a reduced level of plasticity induced crack closure. The curve da/dN versus plastic CTOD range is clearly above the curves for other materials.

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Section: Fcg Analysis Based On Plastic Ctod Rangementioning

confidence: 93%

Fatigue Crack Growth in Maraging Steel Obtained by Selective Laser Melting

et al. 2019

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“…The rate of variation of CTOD p increases progressively with load. In previous works, the plastic CTOD range, δ p , was correlated with fatigue crack growth rate, assuming that FCG is controlled by crack tip plastic deformation and that δ p is able to quantify this deformation.…”

Section: Numerical Determination Of Plastic Ctod δPmentioning

confidence: 99%

“…This explains the inability of d a /d N ‐Δ K models to predict the effect of stress ratio or variable amplitude loading. Therefore, in previous works of the authors, a parameter was used to characterize crack tip deformation which was the plastic portion of crack tip opening displacement (CTOD). Assuming that fatigue crack growth is linked to crack tip cyclic plastic deformation, a model d a /d N ‐ δ p was proposed, where δ p is the range of plastic CTOD.…”

Section: Introductionmentioning

confidence: 99%

Numerical determination of plastic CTOD

Antunes

Díaz

Vasco-Olmo

et al. 2018

Fatigue Fract Eng Mat Struct

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In previous works, a da/dN versus plastic crack tip opening displacement model was proposed to study fatigue crack growth. The plastic crack tip opening displacement, δp, which quantifies the crack tip plastic deformation, is determined numerically using the finite element method. The predictions are affected by different numerical parameters which must be identified and studied. The main parameters are the crack propagation distance, the distance of measurement points relatively to the crack tip, the size of crack tip elements, and the number of load cycles between crack increments. Some crack propagation is required for the stabilization of δp, which occurs when δp reaches its minimum value. The measurement point behind crack tip has a major effect on δp. The peak value occurs at the first node behind crack tip and a progressive decrease of sensitivity is observed with the increase of distance to crack tip. A mesh refinement study showed a coincidence of the predictions obtained with different meshes, which is a good indication for the robustness of the procedure. Finally, there is a significant effect of the number of load cycles between crack increments, NLC, in the presence of crack closure. The increase of NLC reduces the crack opening level and so increases δp.

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“…The crack profiles also express the crack opening displacements, and are interesting to analyze the effect of load history. In a previous work [6], da/dN was related with the range of plastic CTOD, CTODp, for the 7050-T6 aluminum alloy. It was found to be a viable and interesting alternative to K, since it is a local parameter that quantifies crack tip plastic deformation, which is expected to control fatigue crack growth.…”

Section: Introductionmentioning

confidence: 99%

Effect of numerical parameters on plastic CTOD

Antunes¹,

Simões²,

Branco³

et al. 2017

Frattura Ed Integrità Strutturale

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Fatigue crack growth (FCG) is associated with irreversible and non-linear processes happening at the crack tip. This explains different problems observed in the use of da/dN-K curves, namely the inability to explain stress ratio and load history effects. The replacement of K by nonlinear crack tip parameters, namely the crack tip opening displacement (CTOD) is an interesting alternative. However, the determination of CTOD, using the finite element method, depends on different numerical parameters, not sufficiently studied so far. The objective here is to study the effect of these parameters on plastic CTOD, and therefore on da/dN-CTODp curves. A transient behaviour was found at the beginning of numerical crack propagation which is linked to the formation of residual plastic wake. Therefore, a minimum number of crack increments is required to obtain stabilized values. On the other hand, the predicted CTOD p decreases with the distance to crack tip. Close to the crack tip, sensitivity to the measured values is much higher, but it also exists at remote positions. In addition, the mesh has a relatively low influence on CTODp. Finally, the effect of the number of load cycles between crack increments greatly depends on material properties.

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Fatigue crack growth modelling based on CTOD for the 7050‐T6 alloy

Cited by 52 publications

References 77 publications

Fatigue Crack Growth in Maraging Steel Obtained by Selective Laser Melting

Fatigue Crack Growth in Maraging Steel Obtained by Selective Laser Melting

Numerical determination of plastic CTOD

Effect of numerical parameters on plastic CTOD

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