Neutron diffraction measurements of residual stresses around a crack tip developed under variable‐amplitude fatigue loadings

Lee, S. Y.; Rogge, R. B.; Choo, Hahn; Liaw, Peter K.

doi:10.1111/j.1460-2695.2010.01490.x

Cited by 18 publications

(6 citation statements)

References 21 publications

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“…It is well recognized that variable-amplitude cyclic loading can retard or accelerate the crack propagation rate by making it difficult to predict the crack propagation rate and fatigue life [1][2][3][4][5][6]. A tensile overload, a load higher than a maximum load during constant-amplitude cyclic loading, intervened during constant-amplitude cyclic loading is one of the examples to retard the crack propagation rate and increase the fatigue lifetime significantly.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Strain Evolution around a Crack Tip under Steady- and Overloaded-Fatigue Conditions

Lee

Huang

Woo

et al. 2015

Metals

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Abstract:We investigated the evolution of the strain fields around a fatigued crack tip between the steady-and overloaded-fatigue conditions using a nondestructive neutron diffraction technique. The two fatigued compact-tension specimens, with a different fatigue history but an identical applied stress intensity factor range, were used for the direct comparison of the crack tip stress/strain distributions during in situ loading. While strains behind the crack tip in the steady-fatigued specimen are irrelevant to increasing applied load, the strains behind the crack tip in the overloaded-fatigued specimen evolve significantly under loading, leading to a lower driving force of fatigue crack growth. The results reveal the overload retardation mechanism and the correlation between crack tip stress distribution and fatigue crack growth rate.

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Section: Introductionmentioning

confidence: 99%

Dynamic Strain Evolution around a Crack Tip under Steady- and Overloaded-Fatigue Conditions

Lee

Huang

Woo

et al. 2015

Metals

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“…The stress‐intensity factor, K , is obtained by Equation :

K = \frac{P true(2 + α true)}{B \sqrt{W} {(1 - α)}^{3 / 2}} true(0.886 + 4.64 α - 13.32 α^{2} + 14.72 α^{3} - 5.6 α^{4} true),

where α = a / W , a is the crack length, W is the specimen width, B is the specimen thickness, P is the applied load, and the stress‐intensity‐factor range, Δ K is defined by

K = K_{max} - K_{min},

where K max and K min are the maximum and minimum stress‐intensity factors, respectively. The crack‐growth rates (da/dN) and Δ K data were generated by the Material Testing Systems (MTS) machine automatically …”

Section: Materials and Experimental Detailsmentioning

confidence: 99%

Fatigue‐Crack‐Growth Behavior of Two Pipeline Steels

et al. 2016

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The fatigue-crack-growth behavior of two types of pipeline steels, Alloy B [Fe-0.05C-1.52Mn-0.12Si-0.092Nb, weight percent (wt%)] and Alloy C (Fe-0.04C-1.61Mn-0.14Si-0.096Nb, wt%), have been investigated. Compact-tension (CT) specimens have been tested at various frequencies (10, 1, and 0.1 Hz) and different R ratios (0.1 and 0.5, R ¼ P min /P max where P min is the minimum applied load, and P max is the maximum applied load) in air. It is concluded that higher R ratios lead to faster crack-growth rates (FCGRs), while frequency does not have much influence on FCGRs. Moreover, Alloy B tends to have better fatigue resistance than Alloy C under various test conditions in air.

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“…2b). Details of the neutron-diffraction residual stress measurements are presented elsewhere [43,44].…”

Section: Residual Stress Measurements Using Neutron Diffractionmentioning

confidence: 99%

A study on fatigue crack growth behavior subjected to a single tensile overload

et al. 2011

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A study on fatigue crack growth behavior subjected to a single tensile overload : Part I : An overload-induced transient crack growth micromechanism Lee, S. Y.; Liaw, P. K.; Choo, H.; Rogge, R. B.Contact us / Contactez nous: nparc.cisti@nrc-cnrc.gc.ca. AbstractNeutron diffraction and electric potential experiments were carried out to investigate the growth behavior of a fatigue crack subjected to a single tensile overload. The specific objectives were to (i) probe the crack tip deformation and fracture behaviors under applied loads; (ii) examine the overload-induced transient crack growth micromechanism; (iii) validate the effective stress intensity factor range based on the crack closure approach as the fatigue crack tip driving force; and (iv) establish a quantitative relationship between the crack tip driving force and crack growth behavior. Immediately after a single tensile overload was introduced and then unloaded, the crack tip became blunt and enlarged compressive residual stresses in both magnitude and zone size were observed around the crack tip. The results show that the combined contributions of the overload-induced enlarged compressive residual stresses and crack tip blunting with secondary cracks are responsible for the observed changes in the crack opening load and the resultant post-overload transient crack growth behavior.

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Neutron diffraction measurements of residual stresses around a crack tip developed under variable‐amplitude fatigue loadings

Cited by 18 publications

References 21 publications

Dynamic Strain Evolution around a Crack Tip under Steady- and Overloaded-Fatigue Conditions

Dynamic Strain Evolution around a Crack Tip under Steady- and Overloaded-Fatigue Conditions

Fatigue‐Crack‐Growth Behavior of Two Pipeline Steels

A study on fatigue crack growth behavior subjected to a single tensile overload

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