Comparison of two methods to measure crack closure in ultra-high vacuum

Pippan, Reinhard; Haas, Gerald; Stüwe, H.P.

doi:10.1016/0013-7944(89)90269-5

Cited by 16 publications

(5 citation statements)

References 10 publications

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“…The use of PD technique for crack-closure measurements have been debated over the years. [12][13][14][15] It has, however, been shown (see Andersson et al 16,17 ) that crack closure can be accurately measured with PD, especially at low R-values as is the case here. Because of crack sizes and specimen geometries, it would be difficult to use a compliance-based technique for closure measurement.…”

Section: E X P E R I M E N Ta L P R O C E D U R Ementioning

confidence: 57%

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Fatigue crack propagation in Ti–6Al–4V subjected to high strain amplitudes

Andersson

Hansson

Persson

et al. 2004

Fatigue Fract Eng Mat Struct

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A B S T R A C T Fatigue crack propagation in circular Ti-6Al-4V specimens subjected to high strain amplitudes has been investigated. Crack closure was measured with an electrical potential-drop technique. Closure was shown not to depend on strain ratio but to be a function of the applied strain range. At higher strain ranges, the crack was found to be closed for a smaller part of the load cycle than at lower strain ranges due to blunting of the crack tip. Furthermore, the use of a strain-intensity approach to predict crack-propagation rate was investigated, and it was found that for the upper parts of the da/ dN curves the effective strain intensity yields good predictions. Also, the effective stress-intensity factor was found to collapse the da/ dN curves for different load ratios. a = crack length (m) da/ dN = crack-propagation rate per cycle (m/cycle) k = strain-intensity factor (MPa √ m) k eff = effective strain-intensity range (MPa √ m) PD = potential-drop value R ε = strain ratio U = strain intensity ratio K = range of stress-intensity factor (MPa √ m) K eff = effective stress intensity range (MPa √ m) ε = total strain range (%) ε p = plastic strain range (%) σ = total stress range (MPa) σ max = nominal maximum stress (MPa) σ op = nominal opening stress (MPa)

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Section: E X P E R I M E N Ta L P R O C E D U R Ementioning

confidence: 57%

“…By measuring the PD signal during the entire load cycle it was possible to determine the point of crack opening from the curves obtained. The use of PD technique for crack‐closure measurements have been debated over the years 12–15 . It has, however, been shown (see Andersson et al 16,17…”

Section: Methodsmentioning

confidence: 99%

Fatigue crack propagation in Ti–6Al–4V subjected to high strain amplitudes

Andersson

Hansson

Persson

et al. 2004

Fatigue Fract Eng Mat Struct

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“…Barnett and Troiano [60] first used this technique for laboratory research to measure crack growth kinetics in a study of hydrogen embrittlement in notched tensile specimens. Electrical PD methods, which were also named as electrical resistance methods, have been used with success of detection crack closure in fatigue crack studies [61][62][63][64][65][66][67][68][69][70], crack initiation in crackopening displacement and fatigue tests [23,45,46,[71][72][73][74][75][76][77], measurement of crack growth under various of loading conditions (including fatigue [9,21,55,[78][79][80][81], creep [19,21,37,42,[81][82][83][84][85], stress corrosion [21,[86][87][88], sustained loading [89][90][91], fretting fatigue [12], and hydrogen embrittlement [21,…”

Section: Potential Differencementioning

confidence: 99%

Potential difference methods for measuring crack growth: A review

Rouse

Hyde

2020

International Journal of Fatigue

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Non-destructive testing techniques are widely applied in industry for the evaluation of quantities of interest without inflicting additional damage accumulation. Crack detection and monitoring is a prime example of where non-destructive testing is valuable. Among the variety of non-destructive testing techniques, the direct current and alternating current potential difference methods, which are based on the principle that an electrical potential field around a conductive specimen is disturbed by the presence of geometric irregularities (or "features"), have received a great deal of attention in the literature. This is mainly due to the high levels of accuracy associated with these techniques and good estimations of crack initiation and propagation having been achieved.A critical review of the evolution and applications of potential difference methods is presented in this paper. Potential difference methods are capable of providing accurate and continuous measurements with simple installation and exclude the requirement of visual access under harsh service conditions. Alternating current potential difference methods require lower current input than direct current equivalents and hence provide higher sensitivity and offer better noise rejection but are vulnerable to capacitance effects and are more expensive. Calibration curves can be determined analytically, numerically, or by direct or analogue experimental techniques with each method offering strengths and limitations. Application of these should be determined in accordance with the specific scenario. The performance of electric probes (of voltage measurements and current injection) on topand side-face of C(T) and SEN(B) specimens are reviewed in detail as case examples. Specific guidance in normalising measurements and eliminating errors from thermoelectric effects can be implemented in order to improve the accuracy of PD methods. Abundant results have been obtained by applying PD methods in monitoring cracks geometries under aggressive conditions such as corrosion, high temperature, creep and cycled loading.

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“…The third group of techniques try to measure the occurrence of a contact by optical, acoustic or electrical methods . In transparent materials, optical technics can be used to determine both the change of crack tip opening displacement during the load cycle by a Newton interference method and determine the contact area and location .…”

Section: Closure Mechanismsmentioning

confidence: 99%

“…The electrical resistivity of the oxide layer on the fracture surface of most metals and alloys is very high; therefore, the change of the potential drop during the fracture surface contact is very small. Only for fatigue crack propagation in high or ultra‐high vacuum the closure of the fracture surface contacts significantly effects the potential drop . But few friction contacts of the fracture surface causes potential drop changes during the whole loading range, which makes the determination of the mechanically effective contacts difficult.…”

Section: Closure Mechanismsmentioning

confidence: 99%

Fatigue crack closure: a review of the physical phenomena

Pippan

Hohenwarter

2017

Fatigue Fract Eng Mat Struct

Self Cite

276

104

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Plasticity‐induced, roughness‐induced and oxide‐induced crack closures are reviewed. Special attention is devoted to the physical origin, the consequences for the experimental determination and the prediction of the effective crack driving force for fatigue crack propagation. Plasticity‐induced crack closure under plane stress and plane strain conditions require, in principle, a different explanation; however, both types are predictable. This is even the case in the transition region from the plane strain to the plane stress state and all types of loading conditions including constant and variable amplitude loading, the short crack case or the transition from small‐scale to large‐scale yielding. In contrast, the prediction of roughness‐induced and oxide‐induced closures is not as straightforward.

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Comparison of two methods to measure crack closure in ultra-high vacuum

Cited by 16 publications

References 10 publications

Fatigue crack propagation in Ti–6Al–4V subjected to high strain amplitudes

Fatigue crack propagation in Ti–6Al–4V subjected to high strain amplitudes

Potential difference methods for measuring crack growth: A review

Fatigue crack closure: a review of the physical phenomena

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