Use of the ?K-model for evaluation of the period of fatigue crack origin

Panasyuk, V. V.; Ivanitskaya, G. S.; Ostash, О. P.; Zboromirskii, A. I.; Kostyk, E. M.

doi:10.1007/bf00718281

Cited by 2 publications

(3 citation statements)

References 4 publications

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“…Our results show that at normal and low (down to 77 K) temperatures, an increase in grain size causes a decrease of the characteristic distance d * 3 . Additionally, an increase in loading amplitude causes either a decrease or invariability of d *, 31 contrary to the simultaneous permanent increase of the monotonic plastic zone size r pm at the notch tip 32 …”

Section: A Phenomenological Model Of Fatigue Macrocrack Initiationmentioning

confidence: 62%

A phenomenological model of fatigue macrocrack initiation near stress concentrators

Ostash

Panasyuk

Kostyk

1999

Fatigue Fract Eng Mat Struct

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Fatigue macrocrack initiation is considered to be a two‐parameter process. It is governed by the local or strain amplitude, and a certain linear parameter of the material. Corresponding parameters have been proposed, i.e. the local stress range Δσ*y and a characteristic distance d *, the prefracture zone size. The formation of this zone is conditioned by a decrease in yield strength within the material’s surface layers, microstructure, loading amplitude, cyclic strain hardening and environment. The value of d * is estimated experimentally by several methods and is assumed to be a certain material constant, independent of both notch and specimen geometry. At the prefracture zone boundary, a major barrier exists that retards the growth of a physically small fatigue crack. The moment when the physically small crack overcomes the prefracture zone boundary is assumed to be a quantitative criterion, ai = d *, for the micro‐ to macrocrack transition. The proposed relationships, Δσ*y versus Ni , and d * versus Ni , can be used as a basis for the establishment of the materials resistance to macrocrack initiation.

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Section: A Phenomenological Model Of Fatigue Macrocrack Initiationmentioning

confidence: 62%

A phenomenological model of fatigue macrocrack initiation near stress concentrators

Ostash

Panasyuk

Kostyk

1999

Fatigue Fract Eng Mat Struct

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“…However, the crack nucleation period depends on specimen and notch geometry, when such parameters are given. In Refs [4][5][6] this step may be avoided if one chooses as such parameters either the stress c," at a characteristic distance d* from the concentrator tip [4], where d* is a "constant" of the material [5] or, alternatively, the notch tip opening displacement 6, [6] can be chosen. The use of the parameter 0," is based on the supposition that the maximum stress in the notch tip oymax relaxes to this value of 0% as a result of local plastic deformation, and this maximum is located at a distance d* from the tip.…”

Section: Many Structural Elements and Machine Parts Working Under Cycmentioning

confidence: 99%

“…From this solution [6] the normal displacement jump value BA at the point A (opening displacement near the concentrator tip) (Fig. 7), and also the plastic zone length I,, which depend on the level of the applied load F/(a,Rt), are determined.…”

mentioning

confidence: 99%

A New Approach to the Determination of the Macrocrack Nucleation Period Near a Stress Concentrator

Panasyuk

Ivanitska

Ostash

1993

Fatigue Fract Eng Mat Struct

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The stress-strain state of a rectangular plate with a central circular hole and a disc with an edge notch is analyzed both for elastic and elastic-plastic behaviour when cracks emanate from the contours of these concentrators. Stress intensity factors are determined as well as the value of the inelastic deformation at stress concentration zones. The parameters describing the process of crack nucleation are established. The computational results are compared with experimental data when evaluating the period of macrocrack nucleation. NOMENCLATURE a,b = plate length and width d* = the material constant E = Young's modulus G = elastic shear modulus h = thickness of a plate or a disc K, = stress intensity factor (SIF) for the opening mode crack K,$ = SIF for the opening mode of a crack emanating from the concentrator L, = concentrator contour (K = 0); plate or disc contour ( K = I); crack contour ( K = 2.3) I = crack length 1, = length of equivalent crack f , = length of plastic zone 1, = length of a crack emanating from the concentrator N, = number of loading cycles before crack nucleation N ( t K ) , T(tK) = stress components on the L, contour R = disc radius or hole radius in the plate t , = current coordinate of the contour L, u(t,), o(t,) = displacement vector components S , , 86, = notch tip opening displacement (NTOD) and NTOD range (in point A) p = Poisson ratio p = notch radius in the disc uys = yield stress of the material u : , Au:= normal stress and normal stress range at the characteristic distance d* from the concentrator tip uyvmax = maximum stress at the concentrator tip uy(x) = normal stress component along the concentrator axis O(z), Y ( 2 ) = Kolosov-Muskhelishvili complex stress function

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Use of the ?K-model for evaluation of the period of fatigue crack origin

Cited by 2 publications

References 4 publications

A phenomenological model of fatigue macrocrack initiation near stress concentrators

A phenomenological model of fatigue macrocrack initiation near stress concentrators

A New Approach to the Determination of the Macrocrack Nucleation Period Near a Stress Concentrator

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