Edge effects on fatigue crack closure of aluminium alloys

Mahulikar, Deepak; Slagle, W.P.; Marcus, Harris L.

doi:10.1016/0036-9748(79)90176-5

Cited by 8 publications

(3 citation statements)

References 4 publications

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“…There has been considerable debate over whether crack closure occurs under plane strain (out-of-plane constraint) conditions [10,11,25,33,39,40]. Experimental results of Fleck [16] on CT specimens, using the push rod technique, confirm the presence of closure in plane strain.…”

Section: Out-of-plane and In-plane Constraintmentioning

confidence: 70%

“…In the absence of crack face contact, the residual stresses at the crack tip develop from (i) only. Hence, one may see a dependence of crack growth on the R-ratio, stress state, and prior stress history, even when crack closure [37,[68][69][70][71][72][73][39][40] is considered to be small. For example, consider the case where the crack is subjected to tensile loading (R = 0).…”

Section: The Role Of Stresses Ahead Of the Crack Tipmentioning

confidence: 99%

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Recent advances in fatigue crack growth modeling

1996

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Recent advances in our understanding of fatigue crack growth processes and respective crack growth modeling techniques are reviewed. Much of the observed experimental behavior (such as the effects of notches, maximum applied stress, crack length, in-plane biaxiality, out-of-plane constraint, and transient loadings) can be explained based on crack closure concepts. Both Dugdale based models and finite element techniques have been utilized. However, so far neither approach has accounted for crystallographic slip effects, grain orientation effects, or microstructural barriers. A model for crack closure with two microscopic crystallographic slip directions is used to model microscopic cracks. The model predicts variations in closure levels as the orientations of the two slip directions, with respect to the crack growth direction, are changed. In addition, a solution is proposed for the asperity micro-contact problem through a unique roughness induced closure model using a statistical description of asperity heights, asperity densities, and material flow properties. Nomenclature A,B,D----a b = C C ! 61 = C = CCT = CT = di = da/dN = d~P = d-6 = E = .0 P P Ex ~ Ez

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Section: Out-of-plane and In-plane Constraintmentioning

confidence: 70%

Section: The Role Of Stresses Ahead Of the Crack Tipmentioning

confidence: 99%

Recent advances in fatigue crack growth modeling

1996

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“…Mahulikar et al [7] have discussed edge effects on crack closure. Because of the plane stress region at the edges of the compact tension specimen, surface measurements are not representative of the bulk behavior.…”

Section: Introductionmentioning

confidence: 99%

Fatigue Crack Closure and Residual Displacement Measurements on Aluminum Alloys

Mahulikar¹,

Marcus²

1980

Fat Frac Eng Mat Struct

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Ultrasonic bulk measurement technique was used to measure crack closure and a clip-on gage surface measurement technique was used to measure residual displacement at the crack tip of a propagating fatigue crack in 2219 and 7075 aluminum alloys. Experiments were carried out in vacuum, humid air, dry O2 gas, N, gas, and deuteriated water vapor environments to evaluate effects of environments on residual strain and crack closure loads. It was observed that the closure load detected by ultrasonics decreased with introduction of humidity while the residual strain parameter d increased with the humidity. The results are modeled as a build-up of oxide layer in addition to strengthening of asperities on the fracture surface. In the light of these observations, the effectiveness of surface and bulk measurements is evaluated. The results demonstrate that surface measurements are not always representative of the bulk behavior and use of such measurements in predictive analysis for fatigue can be misleading. pc P, and P, P m a n Nomenclature Crack length Residual displacement at the crack tip Thickness of the compact tension specimen Half height of the compact tension specimen Width of the specimen Stress intensity factor Maximum stress intensity factor Minimum stress intensity factor Range in the stress intensity factors (Kmx-Kmin) Crack opening stress intensity factor Effective stress intensity factors range (Kmx-Kop)

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