Potential drop detection of creep damage in the vicinity of welds

Prajapati, Seeran; Nagy, Péter B.; Cawley, P.

doi:10.1016/j.ndteint.2011.11.014

Cited by 15 publications

(7 citation statements)

References 23 publications

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“…Therefore, it could be a valuable addition to our NDE arsenal if Hall coefficient measurements could be conducted in plates or in the subsurface layers of bulk metals. For this purpose, we modified the alternating current potential drop (ACPD) method we recently developed for creep damage monitoring [15,16]. Figure 2 illustrates the concept of electric conductivity anisotropy measurement with a square-electrode ACPD probe.…”

Section: Hall Coefficient Measurementmentioning

confidence: 99%

Hall coefficient measurement for nondestructive materials characterization

Nagy¹

2013

AIP Conference Proceedings

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Articles you may be interested inNondestructive thermoelectric evaluation of the grit blasting induced effects in metallic biomaterials AIP Conf. Proc. 1511, 1504 (2013); 10.1063/1.4789220 Development of nondestructive non-contact acousto-thermal evaluation technique for damage detection in materials Rev. Sci. Instrum. 83, 095103 (2012); 10.1063/1.4749245Characterization of an epoxy bonded aluminum alloy sample applying dynamic acousto elastic testing AIP Conf.ABSTRACT. Although Hall detectors are widely used for magnetic flux density measurements in numerous electromagnetic NDE applications, measurement of the Hall coefficient of metals and their alloys for NDE purposes has not been successfully attempted before. While other intrinsic electric properties, such as electric conductivity and, to a lesser degree, thermoelectric power, are widely used for NDE, Hall coefficient measurements have never been really considered mainly because the measurements are rather difficult to carry out, especially in high-conductivity materials. In contrast to electric conductivity, the Hall coefficient is influenced mainly by the concentration density of the free charge carriers, i.e., electrons in metals, and not so much by their mobility, therefore it could be a valuable addition to our NDE arsenal. We modified the alternating current potential drop (ACPD) method with square-electrode configuration by adding an external bias magnetic field modulation to measure the Hall coefficient. The presence of such a bias field violates the Reciprocity Theorem unless the sign of the magnetic field is switched between the two measurements, which can be exploited to measure the Hall coefficient in the presence of other variations that would otherwise hide it. This new experimental method was tested on paramagnetic alloys and yielded a ±4% reproducibility that probably could be further improved by additional development efforts. As a first step towards illustrating some of the potential applications of this new technique, we have done reversible applied stress measurements in Al 1100 plates and found the sensitivity of the technique to elastic strain surprisingly high.

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Section: Hall Coefficient Measurementmentioning

confidence: 99%

Hall coefficient measurement for nondestructive materials characterization

Nagy¹

2013

AIP Conference Proceedings

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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%

“…) has been further improved by a simultaneous application of a standard and a staggered probe configuration. A directional square-electrode sensor has been developed for creep monitoring in which creep behaviour was related to the variation of the ratio of two resistances measured in orthogonal directions [84,146,147].…”

Section: Probe Configurationmentioning

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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“…In an exploratory test, electrical anisotropy measurements were performed in three regions (base metal, interface zone, and weld region) on four welded specimens cut from a large 0.5%Cr-0.5%Mo-0.25%V low-alloy steel pipe using the above described deployable DACPD probe [50]. All samples were sections of headers with welds, which had been tested by replica examination after operating for about 150,000 hours at 570 °C and 165 bars.…”

Section: Dacpd Creep Assessment With Deployable Electrodesmentioning

confidence: 99%

Investigation of a Novel NDE Method for Monitoring Thermomechanical Damage and Microstructure Evolution in Ferritic-Martensitic Steels for Generation IV Nuclear Energy Systems

Nagy¹

2013

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Page 5 of 78 It should be noted that the operating characteristics of GEN IV high temperature structural components involve long service lives (>60 years). As it is not often practical to perform longterm creep tests under these conditions and obtaining creep-fatigue test data required to determine the negligible creep condition is very challenging because of the long test times that are involved, it is a prudent strategy to compensate for the high uncertainty in the negligible creep conditions by implementing NDE procedures to achieve better health/safety management of nuclear power plants. We conducted an investigation of the feasibility of a novel NDE method that is capable of reliable, in-situ monitoring of creep damage and changes in microstructure of materials and components in the field.During creep deformation, material damage accumulates with time as a function of temperature and mechanical stress. The specific form of degradation is material dependent, but in creep-resistant steels it might follow two main types of path [3]. First, there is transformation and precipitation of carbides from the initial microstructure. These precipitations might be in the form of tempered martensite and bainite or pearlite and ferrite, depending on the heat treatment used. Second, at a later stage of the degradation process, the presence of voids and microcracks becomes more evident. For creep-resistant materials used at high temperatures, creep rupture caused by cumulative damage is a common failure mode. The process starts with the nucleation and then growth of cavities at grain boundaries. The cavities tend to gather preferentially on grain boundaries approximately perpendicular to the applied stress [4][5][6]. Eventually these cavities connect together to form microcracks that propagate and join together in a later stage of degradation that leads to ultimate failure. This process leads to anisotropic texture in electric resistivity, which can be exploited for creep monitoring. In effect, the resulting preference in damage orientation introduces small but perceivable path-length differences for electrical current. This induced anisotropy is detectable by directionally sensitive sensors.Most damage detection techniques have sufficient level of sensitivity for the purposes of damage monitoring, but the crucial issue is their selectivity, or the lack of it, to a specific material degradation mechanism. There are numerous variables to which a given sensor can be sensitive including microstructure evolution, carbide precipitation, hardening, plastic strain and elastic strain. Effective creep monitoring requires that the sensor sufficiently suppress changes that are primarily associated with thermally activated microstructural evolution. Even prior to mechanical loading, the material contains various microdefects, such as microcracks, voids, inclusions, and second-phase particles [7]. Also, most steel components used in power plants accumulate an initial amount of cold work during manufacturing. The presence of cold work ind...

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Potential drop detection of creep damage in the vicinity of welds

Cited by 15 publications

References 23 publications

Hall coefficient measurement for nondestructive materials characterization

Hall coefficient measurement for nondestructive materials characterization

Potential difference methods for measuring crack growth: A review

Investigation of a Novel NDE Method for Monitoring Thermomechanical Damage and Microstructure Evolution in Ferritic-Martensitic Steels for Generation IV Nuclear Energy Systems

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