Electric-Potential Technique for Determining Slow Crack Growth

Anctil, Albert A; Kula, Eric B.; DiCesare, Eugene

doi:10.21236/ad0432497

Cited by 17 publications

(14 citation statements)

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“…On the other hand, some limitations in PD methods have been noted in the literature. Calibration for each test piece geometry and load is required as the accuracy of calibrations seriously affects the capability measurement [42,127]. PD methods are limited to conductive materials [128] because a conducting path around cracks inside the test piece is necessary.…”

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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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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“…Fatigue cracks 0.25 or 0.5 of the width of the panel (2 W ) were grown prior to patching, and after bonding the patch the test pieces were re-inserted into the fatigue machine and crack growth was again monitored continuously by a d.c. potential drop technique [9]. Examples of various CFRP patches bonded to panels are shown in Fig.…”

Section: Fatigue Test Proceduresmentioning

confidence: 99%

Effects of Pre‐moulded Woven CFRP Patches on Fatigue Crack Growth and Residual Strength in 7475‐t761 Aluminium Alloy Sheet

Kemp¹,

Murphy²,

Butt³

et al. 1984

Fatigue Fract Eng Mat Struct

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Fatigue crack propagation tests have been made on 150mm wide panels of 1.6mm thick 7475-T761 clad aluminium alloy sheet with and without adhesively bonded patches of pre-formed carbon fibre reinforced plastic (CFRP). The test frequency was 10 Hz, the minimum stress: maximum stress ratio, R , was 0.1 and the peak applied fatigue stress was 60 MPa.The tests were undertaken to assess the possibility of preventing the growth of fatigue cracks, or reducing their rate of growth, by the application of CFRP patches to one face only of pre-cracked aluminium alloy sheet. The variables examined included the type of patch and adhesive; the size, shape and thickness of the patch; and the effect of chamfering the edges of the patch and the removal of the cladding prior to patching.Results indicated that correctly designed and bonded CFRP patches substantially decreased the subsequent crack growth rate. The size and thickness of the patch had significant effects upon the reduction of fatigue crack growth rate whereas the shape of the patch, chamfering and the removal of the cladding prior to patching had little influence.

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“…Several techniques have been developed for evaluation of fatigue crack area, such as the electrical potential drop method [4] which is widely used in the study of propagation of fatigue cracks. The electrical potential drop method is based on the fact that the discontinuity induced by a crack disturbs the electrical field in a current-carrying body and the magnitude of the disturbance is determined by the size and shape of the crack.…”

Section: Introductionmentioning

confidence: 99%

Dependence of magnetic properties on crack size in steels

Jiles

1998

IEEE Trans. Magn.

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A crack induces a local inhomogeneity in the magnetic flux path in a material and any change in crack area results in change in the distribution of magnetic flux. From the results of measurements on A533B steel and Cr-Mo steels, not only were the magnetic properties found to change with crack area, but also a linear relationship between measured remanence and crack area was observed. A model equation has been developed which shows agreement with the observed relationship. On the other hand, the coercivity and its relationship to crack area were found to depend upon the sensor position relative to the crack. 3D finite element analysis of the leakage field above a crack also showed the position dependence. Therefore, using the remanence measurement method described here fatigue damage and crack area in steel components can be evaluated nondestructively.Index Terms -Crack area measurement, finite element method, leakage field, nondestructive evaluation, steels.

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Electric-Potential Technique for Determining Slow Crack Growth

Cited by 17 publications

References 0 publications

Potential difference methods for measuring crack growth: A review

Potential difference methods for measuring crack growth: A review

Effects of Pre‐moulded Woven CFRP Patches on Fatigue Crack Growth and Residual Strength in 7475‐t761 Aluminium Alloy Sheet

Dependence of magnetic properties on crack size in steels

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