A quantitative evaluation of fatigue crack shielding forces using photoelasticity

Christopher, Colin; James, M.N.; Patterson, E. A.; Tee, Kong Fah

doi:10.1016/j.engfracmech.2008.03.013

Cited by 57 publications

(56 citation statements)

References 31 publications

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“…This necking is a result of a tilting of the crystal lattice generated by dislocation bands (low-angle tilt boundaries) left in the crack wake and causes a transfer of mass along the crack flanks (x-direction) towards the crack front. The associated mass surplus at the crack front results in a near-tip stretching of the material perpendicularly to the crack plane (y-direction) that causes the PICC [1,7,8]. In thin specimens, a ''transversal'' necking in the z-direction can also be produced by dislocations (marked by circles) that move in oblique planes intersecting the crack front in just one point.…”

Section: Plane Stressmentioning

confidence: 97%

“…2 [7,8]. Unlike in the dislocation-based model, the stress field in the continuum model was just intuitively deduced.…”

Section: Plane Stressmentioning

confidence: 97%

“…During the last years, many attempts have been made to incorporate the shielding effects into the LEFM description of the crack-tip stress field. Multiparameter models based on continuum mechanics were recently published [5][6][7][8] and several models dealing with discrete dislocation approaches were also developed, e.g., [1,[9][10][11]. The main advantage of dislocation-based models in comparison with those based on continuum mechanics is their physical transparency that enables us to quantitatively assess both the plasticity-induced and the roughness-induced crack closure (PICC and RICC) components using rather standard materials data.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Dislocation-based model of plasticity and roughness-induced crack closure

Pokluda

2013

International Journal of Fatigue

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Section: Plane Stressmentioning

confidence: 97%

“…2 [7,8]. Unlike in the dislocation-based model, the stress field in the continuum model was just intuitively deduced.…”

Section: Plane Stressmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Dislocation-based model of plasticity and roughness-induced crack closure

Pokluda

2013

International Journal of Fatigue

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“…Since then, this approach has been extensively used by many different authors to report stress intensity factor results for a multiplicity of fracture mechanics problems [7][8][9]. Moreover, the method has been successfully extended to other experimental techniques [10][11][12][13][14] as a standard and straightforward methodology for calculating fracture parameters.…”

Section: Introductionmentioning

confidence: 95%

A Novel Experimental Approach for Calculating Stress Intensity Factors from Isochromatic Data

2009

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In the current paper a new method for calculating the stress intensity factor from isochromatic data is proposed. The method is based on the calculation of a map of the retardation using only the light-and dark-field images of a crack from a circular polariscope. The experimental retardation is compared with the theoretical one predicted by Westergaard's model using between 700 and 800 data points in an array around the crack tip region. In this way, the necessity of unwrapping and calibrating the isochromatic fringe order distribution is avoided and a large potential source of error is eliminated. Subsequently, K I , K II and σ ox are inferred by minimizing an error function. To show the potential and efficacy of the method, K values have been obtained from photoelastic images captured during fatigue tests conducted in a polycarbonate Center-Cracked-Tension (CCT) specimen. Results show an excellent level of agreement with those predicted from theory, highlighting the potential of the proposed methodology.

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“…The internal stresses created by dislocation configurations and secondary phases are to be considered as an important additional factor affecting the crack propagation rate in fatigue. Christopher et al [22,23] proposed a novel mathematical model of the stresses around the tip of a fatigue crack, which considers the effects of wake contact and compatibility-induced stresses at the elastic-plastic boundary. Four parameters were considered to characterize the stress field: an opening mode stress intensity factor K F , the shear stress intensity factor K S , the retardation stress intensity factor K R , and the T-stress.…”

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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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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A quantitative evaluation of fatigue crack shielding forces using photoelasticity

Cited by 57 publications

References 31 publications

Dislocation-based model of plasticity and roughness-induced crack closure

Dislocation-based model of plasticity and roughness-induced crack closure

A Novel Experimental Approach for Calculating Stress Intensity Factors from Isochromatic Data

Effect of crack closure on non-linear crack tip parameters

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