3D shear-mode fatigue crack growth in maraging steel and Ti-6Al-4V

Doquet, Véronique; Bui, Quang‐Hien; Bertolino, G.; Merhy, Elias; Alves, Luis Cardoso

doi:10.1007/s10704-010-9504-7

Cited by 42 publications

(24 citation statements)

References 30 publications

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“…The tubular specimen for mode II under torsion loading in Fig. As found out by Doquet et al 17 , however, a pure mode II and III loading can be achieved only in its very middle section, and consequently, the relevancy of results has to be analysed on the basis of the local values of ΔK II and ΔK III issued from a 3D finite element computation taking the crack front shape into account. 3d, arranged for a four-point bend test as proposed by Chell and Girvan 55 , have been permanently utilized for many years.…”

Section: E X P E R I M E N T a L A R R A N G E M E N T S F O R T E S mentioning

confidence: 99%

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Near‐threshold behaviour of shear‐mode fatigue cracks in metallic materials

Pokluda

Pippan

Vojtek

et al. 2013

Fatigue Fract Eng Mat Struct

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This review paper presents a brief state‐of‐the art of the research on long fatigue shear‐mode cracks and describes some recent results on effective crack growth thresholds and mode I branching conditions achieved by the authors for ARMCO iron, titanium with two different microstructures, nickel and stainless steel. A special technique for preparation of fatigue precracks enabled us to substantially suppress the crack closure (friction) effects at the beginning of the experiment, and the measured threshold values could be considered to be very close to the effective ones. In all investigated materials, the effective thresholds under the remote mode II loading were found to be about 1.7 times lower than those under the remote mode III loading. Effective thresholds under mode II loading of investigated materials were found to follow a simple formula assembled by the shear modulus G, the magnitude of Burgers vector b and a goniometrical function nα of the mean deflection angle that depends on the number of available crystallographic slip systems. These quantities determine the intrinsic material resistance to mode II crack propagation at the threshold. A simple criterion for mode I branching in terms of effective threshold values well reflects a transition from the shear‐mode to the opening‐mode controlled crack propagation at the threshold. The associated transition deflection angle of 40° is a material independent constant.

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Section: E X P E R I M E N T a L A R R A N G E M E N T S F O R T E S mentioning

confidence: 99%

“…[11][12][13][14][15][16][17] Moreover, the negative influence of superimposed out-of-phase cyclic compressive loading on mode III crack growth was observed and discussed in terms of smoothing the crack wake asperities and inducing tensile residual stresses. In fact, the systematic research in this field started only after 1970.…”

Section: Introductionmentioning

confidence: 99%

Near‐threshold behaviour of shear‐mode fatigue cracks in metallic materials

Pokluda

Pippan

Vojtek

et al. 2013

Fatigue Fract Eng Mat Struct

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“…The local nature of the three‐dimensional stress states associated with the vertex (corner) singularities, however, does not implicate that the effect of the vertex singularities on fracture and fatigue behaviour is insignificant and limited to the near free‐surface region. One characteristic example is related to the evolution of the front of a fatigue crack, which is often observed in fatigue tests of plate specimens . It has been argued based on the energy considerations for propagating cracks that the whole crack front should hold square‐root singularity.…”

Section: Introductionmentioning

confidence: 99%

Effect of vertex singularities on stress intensities near plate free surfaces

Kotousov

Berto

2015

Fatigue Fract Eng Mat Struct

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The stress intensity factor (SIF) distribution along the front of a through-the-thickness crack is significantly influenced by the presence of the 3D corner (vertex) singularities. All past 3D finite element studies indicated that for mode I, SIF rapidly decreases near the free surface and for mode II, it sharply increases. From the previous numerical simulations, it is unclear what the limiting values of SIF near the surface are and whether these values are infinite or bounded at the vertex point. In this paper, we conduct a careful finite element study and propose a theoretical equation, which describes the SIF behaviour near the vertex. We demonstrate that the asymptotic behaviour of SIF near the surface is governed by the difference in the strength of the corner and edge singularities. Furthermore, we validate our numerical approach and calculations by utilising the invariant properties of J-integral

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“…The classical criteria for mixed-mode crack propagation [16 -18] do not take these differences into account and do not reflect the physical nature of the process. Such criteria cannot be reliably applied to mode II and mode III crack growth since there is no local mode III growth mechanism adequately efficient with respect to that of the mode II [19,20]. The cracks grow under local mode I or II mechanisms instead [15,21].…”

Section: Introductionmentioning

confidence: 99%

On the connection between mode II and mode III effective thresholds in metals

Vojtek¹,

Žák²,

Pokluda³

2017

Frattura Ed Integrità Strutturale

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ABSTRACT. Closure-free long cracks under the remote mode III loading grow in a more complicated way than those under the remote mode II. For bcc metals, a coplanar in-plane spreading of tongues driven by the local mode II loading components at crack-front asperities prevails while twisting of crack-front segments to mode I, often leading to factory-roof morphology, is typical for other materials. In bcc metals, therefore, the formulation of a quantitative relationship connecting effective thresholds in modes II and III demands to calculate the local mode II components of stress intensity factors at typical asperities of a crack front loaded in the remote mode III. Therefore, a numerical model of a serrated crack front was created and the results were compared with experimentally determined ratio of mode II and III effective thresholds for the ARMCO iron.Although the calculated crack-front roughness needs an experimental verification, the preliminary results indicate that the model can provide a quantitative explanation of the experimentally observed ratio of mode II and mode III effective thresholds in bcc metals. KEYWORDS.Modes II and III; Effective threshold; Micromechanism; Finite element method; ARMCO iron.Citation: Vojtek, T., Žák, S., Pokluda, J., On the connection between mode II and mode III effective thresholds in metals, Frattura ed Integrità Strutturale, 40 (2017) 245-251.

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3D shear-mode fatigue crack growth in maraging steel and Ti-6Al-4V

Cited by 42 publications

References 30 publications

Near‐threshold behaviour of shear‐mode fatigue cracks in metallic materials

Near‐threshold behaviour of shear‐mode fatigue cracks in metallic materials

Effect of vertex singularities on stress intensities near plate free surfaces

On the connection between mode II and mode III effective thresholds in metals

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