Non‐propagation conditions for fatigue cracks and fatigue in the very high‐cycle regime

Pippan, Reinhard; Tabernig, B.; Gach, E.; Riemelmoser, F. O.

doi:10.1046/j.1460-2695.2002.00568.x

Cited by 22 publications

(12 citation statements)

References 24 publications

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“…The shape is similar to that obtained in detailed finite element‐simulations 38 . In ultra‐high vacuum it seems that most of the generated surface during loading shrinks during unloading, only a small part remains for the crack propagation 39,40 . This shrinkage cannot be a simple reversible motion of dislocation, because the involved number of dislocations in the mid and upper Paris regime is too large.…”

Section: The Effect Of Environmentsupporting

confidence: 77%

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On the mechanism of fatigue crack propagation in ductile metallic materials

Pippan

Zelger

Gach

et al. 2010

Fatigue &Amp; Fracture of Engineering Materials &Amp; Structures

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A B S T R A C T An overview of our research performed during the last 15 years is presented to improve the understanding of fatigue crack propagation mechanisms. The focus is devoted to ductile metals and the material separation process at low and intermedial crack propagation rates. The effect of environment, short cracks, small-scale yielding as well as large-scale yielding are considered. It will be shown that the dominant intrinsic propagation mechanism in ductile metallic materials is the formation of new surface due to blunting and the resharpening during unloading. This process is affected by the environment, however, not by the length of the crack and it is independent of large-or small-scale yielding.a = crack length c = Manson-Coffin exponent CTOD = crack tip opening displacement da/dN = fatigue crack propagation rate K max , K min = maximum and minimum stress intensity factor N f = number of cycles to failure R = stress ratio K min /K max CTOD = cyclic crack tip opening displacement ε pl = plastic strain range J = cyclic J-integral J eff = effective cyclic J-integral K = stress intensity rang W e = elastic component of the remote strain energy density range W p = plastic component of the remote strain energy density range σ y = yield stress Figure 1 shows the fatigue crack propagation behaviour of austenitic steel. Such fatigue crack propagation rate, da/dN , versus stress intensity range, K, curves are typical for ductile metals. The fatigue crack propagation behaviour of such materials is characterized by: a steep drop of the crack propagation rate at the threshold of stress intensity range, K th , an extended Paris regime with a Correspondence: R. Pippan. I N T R O D U C T I O N

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Section: The Effect Of Environmentsupporting

confidence: 77%

“…3 3 This can have significant effect of the propagation of cracks from bulk defects and may cause some of the ultrahigh cycle fatigue phenomena 40 …”

mentioning

confidence: 99%

On the mechanism of fatigue crack propagation in ductile metallic materials

Pippan

Zelger

Gach

et al. 2010

Fatigue &Amp; Fracture of Engineering Materials &Amp; Structures

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“…In the crack initiation and early growth stage of VHCF, the crack growth rate is much lower than 10 −10 m/cycle [13,[17][18][19][20]. This indicates that the crack growth in the FGA region occurs first for the most favorable path and does not always extend in all directions in each fatigue cycle.…”

Section: Model and Analysismentioning

confidence: 94%

“…It was shown that the stress intensity factor range at the front of the FGA was a constant and was close to the threshold value of the crack propagation K th . In crack initiation and early growth stage of VHCF, the crack growth rate is much lower than 10 −10 m/cycle [13,[17][18][19][20], and more than 90 % of fatigue life is consumed to form the FGA [21][22][23][24][25]. Therefore, it is essential to develop a model to predict the fatigue life in relation to FGA.…”

Section: Introductionmentioning

confidence: 99%

A two-parameter model to predict fatigue life of high-strength steels in a very high cycle fatigue regime

2015

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In this paper, ultrasonic (20 kHz) fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue (VHCF) regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area (FGA) centered by an inclusion as the crack origin. Then, a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.

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“…The investigation for very-high-cycle fatigue (VHCF) has shown that the crack growth rate in crack initiation and early growth stage is much less than 10 À10 m/cycle (Murakami et al, 1999;Tanaka and Akiniwa, 2002;Sun et al, 2012;Hong et al, 2014). The investigation on fatigue crack behavior in VHCF regime by Pippan et al (2002) also showed that there existed a lower limit for the crack driving force at which cracks did not propagate (da/dN smaller than 10 À13 m/cycle) for constant and variable amplitude loadings. These results suggest that fatigue crack growth still occurs at a very low rate.…”

Section: Dk]mentioning

confidence: 99%