The effect of stress ratio on fatigue crack growth rate in the absence of closure

Sunder, R.; Porter, John R.; Ashbaugh, Noel E.

doi:10.1016/s0142-1123(97)00043-1

Cited by 18 publications

(11 citation statements)

References 10 publications

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“…Klingbeil [73] also observed that without crack closure, the stress ratio has a negligible effect on total energy dissipation per cycle. Sunder et al [59] observed no effect of stress ratio on crack growth rate of long cracks in 2014-T6511 aluminum alloy. The stress ratios studied were R = 0.64; 0.69 and 0.73.…”

Section: Validity Of Crack Closure Conceptmentioning

confidence: 97%

“…The numerical approaches are very interesting for the elimination of contact in order to study its effect, however no studies were reported in literature by the authors. Experimentally the contact of crack flanks has been eliminated considering relatively high stress ratios ( [59]) or removing the wake of the fatigue crack [60]. The experimental determination of non-linear crack tip parameters is also quite difficult, which reinforces the option for the numerical study.…”

Section: Introductionmentioning

confidence: 99%

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Effect of crack closure on non-linear crack tip parameters

Antunes

Sousa

Branco

et al. 2015

International Journal of Fatigue

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Crack closure concept has been widely used to explain different issues of fatigue crack propagation. However, some authors have questioned the relevance of crack closure and have proposed alternative concepts. The main objective here is to check the effectiveness of crack closure concept by linking the contact of crack flanks with non-linear crack tip parameters. Accordingly, 3D-FE numerical models with and without contact were developed for a wide range of loading scenarios and the crack tip parameters usually linked to fatigue crack growth, namely range of cyclic plastic strain, crack tip opening displacement, size of reversed plastic zone and total plastic dissipation per cycle were investigated. It was demonstrated that: (i) LEFM concepts are applicable to the problem under study; (ii) the crack closure phenomenon has a great influence on crack tip parameters decreasing their values; (iii) the ΔKeff concept is able to explain the variations of crack tip parameters produced by the contact of crack flanks; and (iv) the analysis of remote compliance is the best numerical parameter to quantify the crack opening level. Therefore the crack closure concept seems to be valid. Additionally, the curves of crack tip parameters against stress intensity factor range obtained without contact may be seen as master curves.

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Section: Validity Of Crack Closure Conceptmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Effect of crack closure on non-linear crack tip parameters

Antunes

Sousa

Branco

et al. 2015

International Journal of Fatigue

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“…This load sequence consists of two halvesleft half aimed at estimating the crack closure stress, and the right half aimed at estimating the crack opening stress. By design, the left half of the load sequence always results in a higher readout of closure stress in comparison with the one on the right half [15,16]. When viewed in terms of notch root stress-strain response, all the cycles on the left will lie on the falling half of the major hysteresis loop, whereas those on the right will fall on the rising half.…”

Section: Jmda89 © Imeche 2007mentioning

confidence: 99%

“…The most significant is the microscopic nature of measurement that permits one to comprehensively understand the mechanism of crack growth and closure [10][11][12][13]. Examples of application include closure stress mapping across the crack front [10,11], its correlation with near-field laser interferometry and finite element method analysis [12,13], localized closure interaction with mixed-mode conditions [14], crack closure development in short and part-through cracks [15,16], and the discovery of hysteresis in crack closure [6] and its characterization as a function of notch root inelasticity [17] and small crack size.…”

Section: Introductionmentioning

confidence: 99%

Crack closure stress estimation by decodable marker banding techniques and comparison of results with electron fractographic technique

Prakash

Sunder

2007

Proceedings of the Institution of Mechanical Engineers, Part L:

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A specially programmed marker load sequence was designed that permits unambiguous measurement of crack opening and crack closure stress from marker band spacing using both optical and scanning electron fractography. Crack growth tests using programmed marker loading sequence were carried out on single edge notch tension specimens made out of Al-Cu alloy 2014-T3 (BS: L73 equivalent) from crack initiation to failure and the fracture surface examined under optical and electron microscope. Reproducible marker band patterns on the fatigue fracture surface could be obtained using this method. Measured crack closure/opening stress values are observed to be consistent with known material behaviour. The marker banding technique can be applied over wider crack growth rate ranges compared to striation measurement technique, which is restricted to a small range of crack growth rate and in select materials. Quantitative fractography of the marker bands reveals a degree of load interaction under variable amplitude loading that requires further examination.

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“…In previous work, we reported the effect of (closure‐free) high stress ratio and stress level on the growth of naturally forming notch root fatigue cracks 11,12 . A correlation between the two was established.…”

Section: Introductionmentioning

confidence: 96%

The role of air in fatigue load interaction

Sunder¹,

Porter

Ashbaugh

2002

Fatigue Fract Eng Mat Struct

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Natural fatigue crack formation and growth were studied in notched Al–Cu alloy coupons through high‐resolution SEM fractography. The experiments were conducted under programmed loading conditions designed to induce microscopic marking of the crack formation and growth process under varying stress ratio and closure‐free crack tip conditions. Control experiments were performed by switching between an air and vacuum environment. In air, varying the stress ratio from 0.74 down to 0.64 retards crack growth by up to a factor of five. This ‘closure‐free’ stress ratio history effect totally disappears in vacuum, suggesting a significant environmental influence on stress ratio and its history. Crack‐tip stress state appears to moderate environmental action, revealing a potential mechanism sensitive to residual stress. Consequently, crack closure, residual stress and crack front and plane orientation are identified as major load interaction mechanisms whose synergistic action controls fatigue under variable amplitude loading. The study also appears to suggest that as a consequence of the crack seeking the path of least resistance, load‐sequence sensitive crack plane and front orientation may only induce retardation effects.

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The effect of stress ratio on fatigue crack growth rate in the absence of closure

Cited by 18 publications

References 10 publications

Effect of crack closure on non-linear crack tip parameters

Effect of crack closure on non-linear crack tip parameters

Crack closure stress estimation by decodable marker banding techniques and comparison of results with electron fractographic technique

The role of air in fatigue load interaction

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