Fabrication of artificial defects to study internal fatigue crack propagation in metals

Junet, Arnaud; Messager, Alexandre; Boulnat, Xavier; Weck, Arnaud; Boller, Élodie; Helfen, Lukas; Buffière, Jean‐Yves

doi:10.1016/j.scriptamat.2019.05.018

Cited by 20 publications

(17 citation statements)

References 25 publications

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“…The environmental effect on the fatigue damage mechanism was analyzed by several authors. In particular, for Ti6Al4V, Junet [ 22 ] confirmed the results previously obtained by Yoshinaka [ 23 ]: the crack growth rate of internal cracks is lower than cracks initiated from the surface. The real environmental conditions at the crack tip of internal cracks is not known, and it represents still an open point, but it is clear that it has an influence on the crack growth rates [ 24 ].…”

Section: Stress-life-defect Size Modelingsupporting

confidence: 78%

“…From the fracture surface observations, the crack seems to propagate uniformly in all directions from the artificial defects; therefore, considering a shape ratio equal to 1 can be accepted. It is worth noting that this hypothesis was confirmed by Junet et al [ 22 ], who performed in situ synchroton X-ray tomography during fatigue tests, observing that internal cracks after initiation propagate with a regular and almost circular shape. The integration of Equation ( 8 ) requires the initial and the final crack lengths.…”

Section: Stress-life-defect Size Modelingsupporting

confidence: 53%

“…So, internal crack growth rates should be deduced from tests performed in vacuum. In reality, as also suggested by Junet [ 22 ], another possibility would be to directly study the effect of internal defects. The latter approach was the one followed in the present analysis.…”

Section: Stress-life-defect Size Modelingmentioning

confidence: 99%

See 2 more Smart Citations

Effect of Internal Defects on the Fatigue Behavior of Additive Manufactured Metal Components: A Comparison between Ti6Al4V and Inconel 718

et al. 2022

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In order to obtain a widespread application of Additive Manufactured (AM) technology in the aircraft industry for fatigue critical parts, a detailed characterization of the Fatigue and Damage Tolerance (F&DT) behavior of structural components is required. Metal AM techniques in particular are prone to internal defects inherently present due to the nature of the process, which have a detrimental effect on fatigue properties. In the present work, Ti6Al4V and Inconel 718 coupons with artificially induced defects of different dimensions were produced by the Laser Powder Bed Fusion (LPBF) technique. Fatigue tests were performed, and a different defect sensitiveness was observed between the two materials with Inconel being more defect tolerant compared to Titanium. The environmental role at the crack tip of internal defects was discussed, and based on a purely fracture mechanics approach, a simplified stress–life–defect size model was finally devised. The experimental test results together with the information obtained from the fracture surface analysis of tested samples are used to validate the model predictions. The proposed approach could be adopted to define a critical defect size map to be used for tailored Non-Destructive Testing (NDT) evaluation.

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Section: Stress-life-defect Size Modelingsupporting

confidence: 78%

Section: Stress-life-defect Size Modelingsupporting

confidence: 53%

See 1 more Smart Citation

Effect of Internal Defects on the Fatigue Behavior of Additive Manufactured Metal Components: A Comparison between Ti6Al4V and Inconel 718

et al. 2022

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“…Some of the tomographic studies on metals have focused on topics related to quasi‐static defect evolution, [ 114–119 ] corrosion, [ 120 ] fatigue cracks, [ 115–117,119 ] diffusion [ 121 ] or hardness [ 76 ] for which the spatial and temporal resolution is usually not very high. Other studies deal with sintering of metals powders.…”

Section: Resultsmentioning

confidence: 99%

X‐ray Tomography and Tomoscopy on Metals: A Review

et al. 2023

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X‐ray tomography is a versatile tool in materials research and engineering since it allows for a non‐destructive and three‐dimensional mapping of the constituents of a heterogeneous material as long as they differ in their interactions with X‐rays. Recent developments of the technique have brought down the time needed for the acquisition of a single tomogram by many orders of magnitude compared to what was needed 25 years ago. Nowadays, up to 1000 full tomograms can be recorded in a second, which enables real‐time studies of changes in samples caused by reactions or by applied processing operations. The term tomoscopy has been coined for such sequences of 3D images. We review the application of X‐ray tomography and tomoscopy on metals and describe each step required and the associated challenges. A selection of representative investigations is presented with a focus on time‐resolved phenomena in metals and alloys ranging from mechanical deformation, solidification to metals processing processes such as welding and additive manufacturing. Finally likely future developments are discussed.

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“…A lower crack growth rate from internal defects compared to surface defects, as shown in the work of Junet el al. [36] for Ti-6Al-4V alloy or in the work of Serrano- Roughness -As built Munoz et al [37] for a cast aluminium alloy, also contributes to a higher fatigue strength for the internal LoF pore related mechanism. It can also be stated that the classical LEFM approach with a value of ∆K th = 3.9 MPa √ m under-estimates the fatigue strength related to the surface LoF pores mechanism for machined specimens.…”

Section: As-built Specimensmentioning

confidence: 96%

Fatigue behaviour of additively manufactured Ti-6Al-4V alloy: The role of defects on scatter and statistical size effect

Pessard

Morel

et al. 2020

International Journal of Fatigue

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This work is focused on the influence of defects on scatter and statistical size effect of Ti-6Al-4V alloy fabricated by the SLM process. A vast fatigue test campaign has been undertaken, for two surface conditions (as-built and machined surfaces) and two specimen geometries with different highly loaded volume sizes. It was shown, for machined specimens, that a large variety of crack initiation mechanisms is the principal origin of the fatigue scatter. Regarding the size effect, the change of the mechanism is the first order factor that governs the size effect. For as-built specimens, these effects are much less pronounced.

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Fabrication of artificial defects to study internal fatigue crack propagation in metals

Cited by 20 publications

References 25 publications

Effect of Internal Defects on the Fatigue Behavior of Additive Manufactured Metal Components: A Comparison between Ti6Al4V and Inconel 718

Effect of Internal Defects on the Fatigue Behavior of Additive Manufactured Metal Components: A Comparison between Ti6Al4V and Inconel 718

X‐ray Tomography and Tomoscopy on Metals: A Review

Fatigue behaviour of additively manufactured Ti-6Al-4V alloy: The role of defects on scatter and statistical size effect

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