The influence of single and multiple overloads on fatigue crack propagation

Lang, Markus; Marci, G.

doi:10.1046/j.1460-2695.1999.00165.x

Cited by 55 publications

(33 citation statements)

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“…It should be noted that the spatial extent of the monotonic plastic zone is approximately equal to the spatial extent of the overload crack growth retardation effect. This is consistent with long-standing notions that the retardation ceased as the crack tip exhibit the monotonic plastic zone [6][7][8][9]. Beyond the monotonic zone the residual strain is presumed elastic.…”

Section: Experimental Materials and Preparationsupporting

confidence: 73%

“…This behavior is observed for fatigued, overload-fatigued and fatigued-overload-fatigued deformation. The residual stress distributions well behind the crack tip are independent on the fatigue history, thus suggesting a that major driving force of fatigue crack growth is due to the residual stress distributions in the vicinity of the crack tip [5][6][7].…”

Section: "200mentioning

confidence: 94%

“…Here the constant crack growth rate before the overload has been used as a normalization factor. This da/dN curve shows the typical overload retardation affect [6][7][8][9]. This curve was used to estimate the crack lengths to which the cracks in subsequent samples should be grown in order to explore the strain fields at key points on the da/dN curve (see figure).…”

Section: Experimental Materials and Preparationmentioning

confidence: 99%

“…The purpose of this report is to directly correlate variations in crack growth rate with variations in the relevant local strains around the crack tip. The so-called "overload effect", namely the prominent crack growth rate retardation after a single overload cycle in an otherwise constant amplitude fatigue experiment (see for example Figure P 1.1 a), will serve as a vehicle for this comparison [6][7][8][9]. Understanding the important "overload effect" is also a first step in the direction of eventual understanding of the fatigue crack growth under arbitrary variable amplitude loading conditions.…”

Section: Introductionmentioning

confidence: 99%

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Synchrotron Based X-Ray Strain Mapping in Fatigued Materials Subjected to Overload

Tsakalakos¹,

Croft²,

Zhong³

et al. 2007

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing date sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense. Washington Headquarters Services, Directorate for Information Operations and Reports t0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington. VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid 0MB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (D0-MM-YYYY)2. REPORT Fatigue crack growth involves localized fracture at the crack tip, and it intrinsically depends upon the local internal strain/stress fields and accumulated damage in the vicinity of the tip. The purpose of this report is to directly correlate variations in crack growth rate with variations in the relevant local strains around the crack tip. The so-called "overload effect", namely the prominent crack growth rate retardation after a single overload cycle in an otherwise constant amplitude is studied. Our high spatial resolution measurements around fatigue crack are greatly facilitated by indexing our measurements to the fatigue crack itself. This crack based positioning is accomplished by measuring the beam intensity transmitted through the sample, with a transmission detector, so that a radiographic transmission profile can be constructed. Such transmission profiles enabled precise location of the crack and the crack tip in the x-ray beam. SUBJECT Technical Section Technical ObjectivesThe technical objectives of this contract where to use high energy, synchrotron based x-ray diffraction measurements to determine the local strain/stress fields in the vicinity of fatigue crack tips. These strain/stress field measurements were initiated to provide guidance for fundamental modeling of fatigue crack growth. Here it should be noted that such modeling is fundamentally grounded in these local strain/stress fields and that heretofore methods to actually measure these strain fields were essentially nonexistent. (The synchrotron based x-ray diffraction techniques used in this work or developed previously by our group under previous ONR contracts.) The specific focus of this phase of our research was the "overload effect" in which a single cycle overload, in an otherwise constant amplitude fatigued specimen, retards the crack growth rate for a certain number of cycles (or crack length) after the overload (this is described at greater length below). Understanding the overload effect is an important step toward developing models of variable amplitude fatigue loading such as are needed i...

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Section: Experimental Materials and Preparationsupporting

confidence: 73%

Section: "200mentioning

confidence: 94%

Section: Experimental Materials and Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Synchrotron Based X-Ray Strain Mapping in Fatigued Materials Subjected to Overload

Tsakalakos¹,

Croft²,

Zhong³

et al. 2007

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“…In this analysis, the exponent m is assumed to be 2.0, 3.0, and 4.0, which are representative for the range of the measured exponents for structural alloys. A similar expression can be obtained if other crack retardation mechanisms are considered, through Lang and Marci's propagation threshold KPR [14] with A and m parameters fitted for each considered load ratio R:…”

Section: Propagation Of Branched Cracksmentioning

confidence: 99%

Propagation Path and Fatigue Life Predictions of Branched Cracks Under Plane Strain Conditions

Meggiolaro

Miranda

Castro

et al.

Fracture of Nano and Engineering Materials and Structures

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Fatigue cracks can significantly deviate from their Mode I growth direction due to the influence of overloads, multi-axial stresses, micro structural inhomogeneities such as grain boundaries and interfaces, or environmental effects, generating crack kinking or branching [1]. The stress intensity factors (SIF) associated to branched fatigue cracks can be considerably smaller than that of a straight crack with the same projected length, causing crack growth retardation or even arrest. This mechanism can quantitatively explain retardation effects even when plasticity induced crack closure cannot be applied, e.g. in high R-ratio fatigue problems under plane strain conditions. Analytical solutions have been obtained for the SIF of some branched cracks, however numerical methods are the only means to predict the subsequent curved propagation behaviour. In this work, a specialized Finite Element program is used to calculate the propagation path and associated SIF of bifurcated cracks. The numerical calculations are validated through experiments on 4340 steel ESE(T) specimens. A total of 6,250 FE calculations are used to fit empirical equations to the process zone size and crack retardation factor along the curved crack branches. The bifurcation simulations include several combinations of bifurcation angles, branch asymmetry ratios, crack growth exponents, and even considers interaction between crack branching and other retardation mechanisms such as crack closure, assuming the crack opening level is well known.

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The Effect of Overloads on the Fatigue Life

Lassen¹,

Récho²

2006

Fatigue Life Analyses of Welded Structures

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The influence of single and multiple overloads on fatigue crack propagation

Cited by 55 publications

References 0 publications

Synchrotron Based X-Ray Strain Mapping in Fatigued Materials Subjected to Overload

Synchrotron Based X-Ray Strain Mapping in Fatigued Materials Subjected to Overload

Propagation Path and Fatigue Life Predictions of Branched Cracks Under Plane Strain Conditions

The Effect of Overloads on the Fatigue Life

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