Feasibility Study of Alternating Current Potential Drop Techniques for Elastic-Plastic Fracture Toughness Testing

Tregoning, Robert L.

doi:10.1520/stp11540s

Cited by 1 publication

(9 citation statements)

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“…When using compliance methods, periodic unloading at regular crack growth intervals is applied to the specimen and measurements are recorded discretely. For this reason, these methods are not applicable for testing under dynamic or rapid loading [4,45,46]. Moreover, the methods are limited for applications of aggressive environments such as creep, corrosion and high temperature (higher than 175 ℃ according to [45]) [4,45,47,48].…”

Section: Compliancementioning

confidence: 99%

“…For this reason, these methods are not applicable for testing under dynamic or rapid loading [4,45,46]. Moreover, the methods are limited for applications of aggressive environments such as creep, corrosion and high temperature (higher than 175 ℃ according to [45]) [4,45,47,48]. The infeasibility at high temperature is presumably due to the lack of available displacement gauges and the potential influence of stress relaxation at crack tip during unloading [4].…”

Section: Compliancementioning

confidence: 99%

“…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%

“…A noticeable improvement offered by the ACPD method is the introduction of phase sensitive detection associated with lock-in amplifiers that offer excellent noise rejection and improved accuracy and sensitivity for ACPD measurements [22,34,76,88,124,137,140]. In the excitation circuits a reference signal provided by a voltage controlled oscillator is fed into a power amplifier for constant current output [34,45,48,133,134,140,150]. Similar to DCPD system, a reference resistor connected in series with the test-piece maintains the stability of current regardless of the specimen resistance [34,134,140].…”

Section: Experimental System Designsmentioning

confidence: 99%

“…The determination of calibration curves is found to significantly influence the accuracy of the method [56]. Several work have determined calibration curves and obtained linear [21,22,34,76,134,140,153,154] or non-linear [45,46,56,75,80,129,133,[155][156][157][158] relation between PDs and crack lengths. The linearity of calibration curves was regarded as an advantage of the PD technique over the other NTD methods [41,76].…”

Section: Introductionmentioning

confidence: 99%

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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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