Electrical potential drop method for evaluating crack depth

Ikeda, Kiyohiro; Yoshimi, M.; Miki, Chitoshi

doi:10.1007/bf00037037

Cited by 20 publications

(14 citation statements)

References 6 publications

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“…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%

“…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]. The output signals from specimen are isolated and pre-amplified at a transformer [34,40,140,149,150] and measured with a lockin amplifier. Only the potential signals at the reference frequency identical to the current source will be amplified and accepted by the lock-in amplifier [34,137,140] (a signal-to-noise ratio as low as 0.1 is allowed by lock-in amplifiers [34,140]).…”

Section: Experimental System Designsmentioning

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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Section: Experimental System Designsmentioning

confidence: 99%

Section: Experimental System Designsmentioning

confidence: 99%

Potential difference methods for measuring crack growth: A review

Rouse

Hyde

2020

International Journal of Fatigue

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“…Any change in the geometry through cracking will induce a change in resistance. Through correct calibration, this change in resistance can be related to crack growth [61]. To allow implementation of this technique during the testing of the specimen, measurement probes are installed either side of the central hole and a reference probe is installed away from the stress concentration for comparison purposes.…”

Section: Arrangement Of Experimental Test Specimenmentioning

confidence: 99%

A novel simulation for the design of a low cycle fatigue experimental testing programme

Beesley

Chen

Hughes

2017

Computers & Structures

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This paper proposes an innovative concept for the design of an experimental testing programme suitable for causing Low Cycle Fatigue crack initiation in a bespoke complex notched specimen. This technique is referred to as the Reversed Plasticity Domain Method and utilises a novel combination of the Linear Matching Method and the Bree Interaction diagram. This is the first time these techniques have been combined in this way for the calculation of the design loads of industrial components. This investigation displays the capabilities of this technique for an industrial application and demonstrates its key advantages for the design of an experimental testing programme for a highly complex test specimen

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“…The boundaries are traction-free apart from where the specimen is in contact with cylinders A, B and C. Thus, the shear stresses t 1 2 and 7 1 3 and the displacement u 1 in the x,-direction is ~1 = 712 = 7 1 3 = 0 (1) at cylinders B and C at x 1 = -W,, lx21 = W 2 and Ix31 d W,.…”

Section: Statement Of the Problemmentioning

confidence: 99%

“…Thus, the mechanical problcm for body ( x l I 6 Wl, 0 G x2 6 W , and 0 6 x3 d W , is given by the boundary conditions (1) (3), (8) and (9). Figure 5 shows the mechanical boundary conditions in the x1 -x2 plane.…”

Section: Statement Of the Problemmentioning

confidence: 99%

Crack length measurements with a potential drop method: A finite element simulation

Ståhle

1993

Numerical Meth Engineering

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A potential drop method, as used for estimations of crack lengths during three-point-bend experiments, is studied. The mechanical slate is calculated using a finite element method. The deformed body obtained is used for a subsequent calculation of the electrostatic state. Calculations are performed for both two-and three-dimensional models. The material is assumed to be elastic, linearly hardening plastic and electrostatically linear. Large deformations are considered. Further, the non-linearity caused by the load, depending on the contact area between the cylinder on which the load is applied and the specimen, is considered. The increased contact area did not influence the mechanical state very much but had a direct impact on the electrostatic state. The changes in the potential drop recordings due to deformation and electrical current passing through the load cylinder were shown to be considerable. The study explains, at least partly, the experimental observations. A more reliable registration of crack growth initiation is the main outcome of the analysis.

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Electrical potential drop method for evaluating crack depth

Cited by 20 publications

References 6 publications

Potential difference methods for measuring crack growth: A review

Potential difference methods for measuring crack growth: A review

A novel simulation for the design of a low cycle fatigue experimental testing programme

Crack length measurements with a potential drop method: A finite element simulation

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