A study of the crack wake closure/opening behaviour of short fatigue cracks and its influence on crack growth

Zhang, X.P.; Wang, Chun H.; Ye, Lin; Mai, Yiu‐Wing

doi:10.1016/j.msea.2005.06.034

Cited by 20 publications

(2 citation statements)

References 34 publications

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“…Measurements at the surface of a sample during a loading/unloading cycle have been performed using for example scanning electron microscopy [4]. Surface measurements allow one to visualize crack shapes and to analyze closure changes with the crack length [5].…”

Section: Introductionmentioning

confidence: 99%

Crack closure and stress intensity factor measurements in nodular graphite cast iron using three-dimensional correlation of laboratory X-ray microtomography images

et al. 2009

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3D tomographic images of a nodular graphite cast iron obtained using a laboratory X-ray source were used to analyze the opening of a fatigue crack during in-situ mechanical loading. Direct image analysis and digital image correlation are utilized to obtain the 3D morphology and front location of the crack as well as the displacement fields in the bulk of the specimen. From DIC results, it is possible to extract the Crack Opening Displacement (COD) map in the whole sample cross-section and to compute Stress Intensity Factors (SIF) all along the crack front even for COD values that are less than the image resolution. The comparison of COD maps with local values of SIF enabled for an estimation of the opening SIF, K op , equal to 6 MPa√m.

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Section: Introductionmentioning

confidence: 99%

Crack closure and stress intensity factor measurements in nodular graphite cast iron using three-dimensional correlation of laboratory X-ray microtomography images

et al. 2009

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“…To observe deformation mechanisms in the vicinity of the fatigue crack tip, use of in‐situ scanning electron microscope (SEM) observations is a powerful technique 4,5 . High resolution images can be taken at different load levels, and by comparing images, changes in displacements can be determined.…”

Section: Introductionmentioning

confidence: 99%

Determination of displacements around fatigue cracks using image analysis of in‐situ scanning electron microscope images

Jacobsson

Persson

Melin

2008

Fatigue Fract Eng Mat Struct

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A B S T R A C T A technique to in-situ measure the displacements in the vicinity of the crack tip during fatigue crack propagation has been developed. High-resolution images of the crack tip were taken continuously throughout the fatigue load cycles with a scanning electron microscope (SEM), and an image analysis program was used to determine the displacements at different positions with respect to the crack tip. The displacements were then used to determine crack shapes and compliance curves. The measured crack shapes show a general √ r dependence versus the distance to the crack tip. However, close to the crack tip the crack shape is clearly affected by plastic deformation, even in cases when small scale yielding prevails. The compliance curve measurements close to the crack tip can be used to determine the global stress level when the crack surfaces are separated, so that the exact opening and closure stresses can be determined. N O M E N C L A T U R E A cs = specimen cross section area (m 2 )A = specimen surface area used by the cross correlation function a = projected crack length (m) E = Young's modulus (Pa) F = applied global load (N) K = stress intensity factor (Pa √ m) L = specimen length (m) v = displacement perpendicular to the load direction W = specimen width (m) α = the identified specimen surface area, used to measure the displacement δ = crack opening displacement θ = angle from crack direction ( • ) υ = Poisson's ratio σ = stress (Pa) σ ys = yield stress (Pa)

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Near-threshold fatigue propagation of physically through-thickness short and long cracks in a low alloy steel

Pham¹,

Tran²,

Chrétien

et al. 2014

J Mater Sci

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International audienceIn this paper, the near-threshold fatigue behavior of physically through-thickness short cracks and of long cracks in a low alloy steel is investigated by experiments in ambient air. Physically through-thickness short fatigue cracks are created by gradually removing the plastic wake of long cracks in compact tension specimens. The crack closure is systematically measured using the compliance variation technique with numerical data acquisition and filtering for accurate detection of the stress intensity factor (SIF) at the crack opening. Based on the experimental results, the nominal threshold SIF range is shown to be dependent on the crack length and the characteristic of the crack wake which is strongly dependent on the loading history. The effective threshold SIF range and the relation between the crack propagation rate and the effective SIF range after the crack closure correction are shown to be independent on crack length and loading history. The shielding effect of the crack closure is shown to be related to the wake length and load history. The effective threshold SIF range and the relationship between the crack growth rate and the effective SIF range appear to be unique for this material in ambient air. These properties can be considered as specific fatigue properties of the couple material/ambient air environment

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A study of the crack wake closure/opening behaviour of short fatigue cracks and its influence on crack growth

Cited by 20 publications

References 34 publications

Crack closure and stress intensity factor measurements in nodular graphite cast iron using three-dimensional correlation of laboratory X-ray microtomography images

Crack closure and stress intensity factor measurements in nodular graphite cast iron using three-dimensional correlation of laboratory X-ray microtomography images

Determination of displacements around fatigue cracks using image analysis of in‐situ scanning electron microscope images

Near-threshold fatigue propagation of physically through-thickness short and long cracks in a low alloy steel

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