The effect of a free surface on fatigue crack behaviour

Hutař, Pavel; Náhlík, Luboš; Knésl, Zdeněk

doi:10.1016/j.ijfatigue.2010.01.009

Cited by 50 publications

(27 citation statements)

References 17 publications

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“…The importance of three dimensional effects in fracture of plate components is well documented by past and recent investigations showing the crescent interest of the scientific community in this topic (Benthem, 1977, Bazant andEstenssoro, 1979;Maz'ya and Nazarov, 1989, Kozlov et al, 1992Pook, 1994Huang, 2004, Hutar et al, 2010. A wide review of these effects has been recently carried out by Kotousov et al (2010).…”

Section: Introductionmentioning

confidence: 97%

On the Presence of the Out–of–Plane Singular Mode Induced by Plane Loading With KII = KI = 0

2010

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Previous studies by a number of researchers demonstrated that in the case of a plane crack subjected to shear loading conditions characterized by a remote stress intensity factor, K II , a three-dimensional singular mode (called mode O or outof-plane mode) develops at the crack tip. This singular mode occurs due to the primary shear loading and Poisson's effect. Similar to mode III, the O-mode is associated with the transverse shear stress components. Recent theoretical and numerical studies have also demonstrated a strong presence of this singular mode in plates weakened by pointed V-notches. Therefore, it was suggested that O-mode can play an important role in fracture initiation, particularly at large opening angles (above 102.6 o ) when the applied mode II is non-singular. One exciting development in 3D fracture mechanics is to investigate this singular mode when the remote anti-symmetric loading doesn't produce the in-plane singularities, or when K II (K I ) = 0 for plane problems with cracks. In this case, the classical energy fracture criterion, which is based on the plane theory of elasticity, indicates zero energy release rate at the crack tip; which, generally speaking, excludes the possibility of brittle fracture by crack extension. In this letter we will demonstrate that when K II = 0, the three-dimensional effects, in particular the presence of the singular mode O coupled with the plane shear loading, can lead to non-zero energy release rate and provoke the fracture initiation at the crack tip.

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Section: Introductionmentioning

confidence: 97%

On the Presence of the Out–of–Plane Singular Mode Induced by Plane Loading With KII = KI = 0

2010

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“…In case of a straight crack, the value of the stress singularity exponent in the intersection between crack front and free surface is always smaller then 0.5 [4], [5]. Lower value of the stress singularity causes a decrease of the fatigue crack propagation rate [6], [9]. Main effect of the free surface is that the fatigue crack does not grow as a straight line, but the crack front is typically curved.…”

Section: Introductionmentioning

confidence: 99%

The Effect of the Free Surface on the Singular Stress Field at the Fatigue Crack Front

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Náhlík

et al. 2017

Strojnícky Casopis – Journal of Mechanical Engineering

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Description of stress singularity in the vicinity of a free surface is presented. Its presence causes the retardation of the fatigue crack growth in that region and fatigue crack is being curved. Numerical model is used to study dependence of the stress singularity exponent on Poisson's ratio. Estimated values are compared to those already published. Experimentally measured angles of fatigue crack on SENB specimens confirm the relation between Poisson's ratio and the angle between crack front and free surface.

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“…Hutar et al [30,31] presented a very interesting methodology based on generalised SIF to describe crack behaviour close to the free surface. They studied the evolution of the crack shape due to the free surface influence and his relevance with the structure thickness.…”

Section: Introductionmentioning

confidence: 99%

“…Most common method is the extrapolation of the displacement in the vicinity of the crack using LEFM analytical expressions [16][17][18][19]. On the other hand we have energetic methods as the strain energy density (SED) [30][31][32] or J-integral [20,24].…”

Section: Introductionmentioning

confidence: 99%