In-Situ Creep Monitoring Using the Potential Drop Method

Madhi, E.; Sposito, G.; Davies, Catrin M.; Cawley, P.; Nagy, Péter B.

doi:10.1063/1.3592124

Cited by 7 publications

(10 citation statements)

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“…Disadvantages of ACPD include higher investment due to the amplification and filtering equipment [48,76,137], and disturbance on calibration caused by capacitance effect such as change in permeability and conductivity [20,31,32,131,137]. In order to minimise spurious effects caused by magnetic properties, low frequency ACPD measurements were proposed in which some of the advantages of ACPD were conserved, yet the noise rejection was improved by suppressing the skin effect [84,85,[146][147][148].…”

Section: Comparison Between Dcpd and Acpdmentioning

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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Section: Comparison Between Dcpd and Acpdmentioning

confidence: 99%

Potential difference methods for measuring crack growth: A review

Rouse

Hyde

2020

International Journal of Fatigue

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“…Normal resistance for a probe on the second side (σ 2 ) of the boundary In-phase voltage drop in the lateral direction V (11) Electric potential when the injection and sensing points are located on the first side (σ 1 ) of the plane boundary separating two conducting quarter spaces V (12) Electric potential when the injection point is on the first side (σ 1 ) and sensing point is on the other side (σ 2 ) of the plane boundary separating two conducting quarter spaces V (21) Electric potential when the injection point is on the second side (σ 2 ) and sensing point is on the first side (σ 1 ) of the plane boundary separating two conducting quarter spaces V (22) Electric potential when the injection and sensing points are located on the second side (σ 2 ) of the plane boundary separating two conducting quarter spaces observed after the load is applied followed by the deceleration of the strain rate due to strain hardening process until a steady creep rate is achieved which characterizes the primary creep stage. The secondary creep stage is characterized by a slow but constant plastic flow of material representing a balance between strain hardening and the softening and damage processes.…”

Section: List Of Tablesmentioning

confidence: 99%

“…When the injection and sensing points are located on the first side (σ 1 ) of the plane boundary separating two conducting quarter-spaces, the electric potential can be written as respectively, the potential distribution can be written as when the injection and sensing points are on the opposite sides of the plane boundary. When the injection and sensing points are both located on the second side (σ 2 ) of the boundary, the potential V (22) can be obtained from Eq. (4.17) by simply replacing σ 1 with σ 2 and vice versa.…”

Section: Analytical Predictionsmentioning

confidence: 99%

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Potential drop detection of creep damage in the vicinity of welds

Prajapati

Nagy

Cawley

2012

AIP Conference Proceedings

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“…6. The 'thin' component DC resistance for a square electrode configuration is again provided by Madhi [24]:…”

Section: Ac Asymptote: the Reduced-thickness Modelmentioning

confidence: 99%

Compensation of the Skin Effect in Low-Frequency Potential Drop Measurements

Corcoran

Nagy

2016

J Nondestruct Eval

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Potential drop measurements are routinely used in the non-destructive evaluation of component integrity. Potential drop measurements use either direct current (DC) or alternating current (AC), the latter will have superior noise performance due to the ability to perform phase sensitive detection and the reduction of flicker noise. AC measurements are however subject to the skin effect where the current is electromagnetically constricted to the surface of the component. Unfortunately, the skin effect is a function of magnetic permeability, which in ferromagnetic materials is sensitive to a number of parameters including stress and temperature, and consequently in-situ impedance measurements are likely to be unstable. It has been proposed that quasi-DC measurements, which benefit from superior noise performance, but also tend to the skin-effect independent DC measurement, be adopted for in-situ creep measurements for power station components. Unfortunately, the quasi-DC measurement will only tend to the DC distribution and therefore some remnant sensitivity to the skin effect will remain. This paper will present a correction for situations where the remnant sensitivity to the skin effect is not adequately suppressed by using sufficiently low frequency; the application of particular interest being the in-situ monitoring of the creep strain of power station components. The correction uses the measured phase angle to approximate the influence of the skin effect and allow recovery of the DC-asymptotic value of the resistance. tial drop measurements are minimum phase is presented and illustrated on two cases; the creep strain sensor of practical interest and a conducting rod as another common case to illustrate generality. The correction is demonstrated experimentally on a component where the skin effect is manipulated by application of a range of elastic stresses.

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In-Situ Creep Monitoring Using the Potential Drop Method

Cited by 7 publications

References 0 publications

Potential difference methods for measuring crack growth: A review

Potential difference methods for measuring crack growth: A review

Potential drop detection of creep damage in the vicinity of welds

Compensation of the Skin Effect in Low-Frequency Potential Drop Measurements

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