Observation of 3D shape and propagation mode transition of fatigue cracks in Ti–6Al–4V under cyclic torsion using CT imaging with ultra-bright synchrotron radiation

Shiozawa, Daiki; Nakai, Yoshikazu; Murakami, T.; Nosho, H.

doi:10.1016/j.ijfatigue.2013.02.018

Cited by 21 publications

(18 citation statements)

References 17 publications

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“…For both titanium alloys branching starts before the internal crack reaches the specimen surface. This result is different from the result obtained for the Ti-6Al-4V alloy in the HCF regime by Shiozawa et al [31]. In reference [31] fully reversed torsion fatigue tests were carried out on the Ti-6Al-4V titanium alloy in the HCF regime at a loading frequency of 10 Hz.…”

Section: Discussionmentioning

confidence: 63%

“…This result is different from the result obtained for the Ti-6Al-4V alloy in the HCF regime by Shiozawa et al [31]. In reference [31] fully reversed torsion fatigue tests were carried out on the Ti-6Al-4V titanium alloy in the HCF regime at a loading frequency of 10 Hz. It was shown that in HCF a torsion crack first grows in the depth of the material and afterwards it branches at the surface without growing deeper.…”

Section: Discussionmentioning

confidence: 63%

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Comparison of crack paths in a forged and extruded aeronautical titanium alloy loaded in torsion in the gigacycle fatigue regime

Nikitin

Palin‐Luc

Shanyavskiy

et al. 2016

Engineering Fracture Mechanics

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. This is an author-deposited version published in: https://sam.ensam.eu Handle IDa b s t r a c t This paper discusses features of fatigue crack initiation and growth in an extruded and forged VT3-1 titanium alloy loaded in pure torsion in the gigacycle regime. Torsion fatigue tests were performed at 20 kHz up to a fatigue life of 10 9 cycles. It has been shown that regardless of the manufacturing process both surface and subsurface crack initiation may appear under ultrasonic torsion loads despite the fact that the maximum shear stress amplitude is located at the specimen surface. In the two cases cracks initiate on planes of maximum shear stress amplitude (mode II). After reaching a certain length the cracks turn and propagate in mode I. Surface crack initiation and growth mechanisms in VHCF regime are similar to HCF ones. Subsurface crack forms a typical ''fish-eye" pattern on fracture surface with three different zones: (1) small crack growth in the plane of maximum shear stress, (2) crack growth on the plane of maximum normal stress with the formation of a quasi-flat failure surface covered by fretting debris, (3) crack branching under mixed mode loading conditions (I + II + III) with the formation of several secondary cracks. Subsurface crack initiation sites are located below the specimen surface (at a depth of approximately 200 lm) for both the forged and the extruded materials. Subsurface crack growth is observed on the failure surface as being less rough. The mechanisms of subsurface crack initiation seems to be similar to these observed under fully reversed tensile loads.

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Section: Discussionmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 63%

Comparison of crack paths in a forged and extruded aeronautical titanium alloy loaded in torsion in the gigacycle fatigue regime

Nikitin

Palin‐Luc

Shanyavskiy

et al. 2016

Engineering Fracture Mechanics

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show abstract

“…This could also happen in the bulk. If a small kink crack forms at the crack tip in the bulk (or at the surface), because of the local crystallography, the values of the mode I stress intensity factor will increase rapidly [4] and mode I growth can take place. …”

Section: Resultsmentioning

confidence: 99%

“…The link between surface observations and fracture surfaces where crack growth can be very complex is however difficult to establish and the detailed chronology of crack growth in the sample interior is lost. The 3D shape of a fatigue crack growing inside a Ti alloy has been analyzed using X ray tomography [4]; although this is a considerable improvement compared to the aforementioned observations the images were obtained during ex situ experiments providing pictures of unloaded cracks. In this paper, we report results on the initiation and propagation of fatigue cracks during cyclic torsion loading of a cast Al alloy (A 357).…”

Section: Introductionmentioning

confidence: 99%

3D Analyses of crack propagation in torsion

Shiozawa¹,

Munoz²,

Dancette³

et al. 2015

Frattura Ed Integrità Strutturale

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ABSTRACT. The initiation and propagation of fatigue cracks during cyclic torsion loading was studied in a cast Al alloy (A357) with a relatively large (~500 µm) grain size. 2D observations, revealed that multi site crack initiation occur on the {111} slip planes exhibiting the highest slip activity (iso-strain Taylor analysis), preferentially on planes nearly perpendicular to the sample axis. Within the first grain, the cracks have a pronounced crystallographic propagation mode (mode II crack growth) and strongly interact with the grain boundaries. In situ 3D monitoring of torsion fatigue tests using synchrotron X-ray tomography reveal that propagation towards the interior of the samples occurs first along the sample periphery in mode II leading to relatively shallow cracks which penetrate towards the sample center only after a large number of cycles is reached .The values of mode I, II and III stress intensity factors have been calculated from finite element simulation at the tip of the shallow mode II crack. Those values are used to analyse the bulk propagation of the observed cracks.

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“…The absorbed energy of dimples (nucleation and growth of micro‐voids) is much greater than the surface energy of cleavage planes . Consequently, the size and distribution of dimples in the flat fracture region would reflect qualitatively the mechanical properties of ductile materials . In the previous studies, the shear fracture energy would be ignored by increasing the specimen thickness for measuring fracture toughness by the linear‐elastic fracture mechanic (e.g., K IC ) or fused by the elastic‐plastic (e.g., J integral and CTOD method) fracture mechanic .…”

Section: Introductionmentioning

confidence: 99%

The Minimum Energy Density Criterion for the Competition between Shear and Flat Fracture

Zhang

et al. 2018

Adv Eng Mater

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It is generally recognized that the fracture toughness K IC of materials represents the crack resistance during fracture, i.e., the energy consumption. In this study, AISI 4340 steels with different strength are applied to systematically investigate the intrinsic mechanism of fracture toughness. It is found that the fracture surface morphologies of AISI 4340 steels change from quasi-cleavage fracture to dimple fracture with increasing the tempering temperature. While, the specimen size has almost no effect on the fracture mechanism of shear/flat fracture region, demonstrating that the fracture toughness depends on the proportion of shear and flat fracture region. Additionally, the shear lip width of the K IC specimen will increase to a constant value with enhancing the specimen thickness. Based on the energy balance principle, the maximum shear lip width can be obtained at the minimum fracture energy density of materials; consequently, there is an essential relationship between the shear fracture and fracture toughness, i.e., the minimum energy density criterion. The new finding, which provides a scaling law to well evaluate the plane strain fracture toughness of new materials with high toughness (e.g., nanostructured materials and metallic glasses), may broad the understandings on the fracture toughness.

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Observation of 3D shape and propagation mode transition of fatigue cracks in Ti–6Al–4V under cyclic torsion using CT imaging with ultra-bright synchrotron radiation

Cited by 21 publications

References 17 publications

Comparison of crack paths in a forged and extruded aeronautical titanium alloy loaded in torsion in the gigacycle fatigue regime

Comparison of crack paths in a forged and extruded aeronautical titanium alloy loaded in torsion in the gigacycle fatigue regime

3D Analyses of crack propagation in torsion

The Minimum Energy Density Criterion for the Competition between Shear and Flat Fracture

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