Thin-Skin Electromagnetic Fields Around Surface-Breaking Cracks in Metals

Lewis, A. M.; Michael, D. H.; Lugg, Martin; Collins, R.

doi:10.1007/978-1-4613-0817-1_30

Cited by 24 publications

(26 citation statements)

References 5 publications

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“…Fig.1.a) shows that when a surface crack with depth d exists, redistribution current flows along the crack profile [13]. Moreover, the crack causes additional current path and a larger potential drop [14]. I（ f ） is the AC excitation current with frequency f, and Δ is the distance between each pair of electrodes.…”

Section: Acpd Principlementioning

confidence: 99%

Novel Method for Sizing Metallic Bottom Crack Depth Using Multi-frequency Alternating Current Potential Drop Technique

Gan

Wan

et al. 2015

Measurement Science Review

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Potential drop techniques are of two types: the direct current potential drop (DCPD) technique and alternating current potential drop (ACPD) technique, and both of them are used in nondestructive testing. ACPD, as a kind of valid method in sizing metal cracks, has been applied to evaluate metal structures. However, our review of most available approaches revealed that some improvements can be done in measuring depth of metal bottom crack by means of ACPD, such as accuracy and sensitivity of shallow crack. This paper studied a novel method which utilized the slope of voltage ratio-frequency curve to solve bottom crack depth by using a simple mathematic equation based on finite element analysis. It is found that voltage ratio varies linearly with frequency in the range of 5-15 Hz; this range is slightly higher than the equivalent frequency and lower than semi-permeable frequency. Simulation and experiment show that the novel method can measure the bottom crack depth accurately.

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Section: Acpd Principlementioning

confidence: 99%

Novel Method for Sizing Metallic Bottom Crack Depth Using Multi-frequency Alternating Current Potential Drop Technique

Gan

Wan

et al. 2015

Measurement Science Review

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“…The Alternating Current Field Method (ACFM) allows non-contact detection and sizing of surface breaking cracks in pipes by inducing a uniform high frequency electric current in the surface of the pipe and measuring current deflection around defects by monitoring changes in the induced magnetic field [33,34]. The technique can be applied outside of a coating up to 10 mm thick [35], is fast and does not require instrument calibration before use [36].…”

Section: Introductionmentioning

confidence: 99%

Current deflection NDE for the inspection and monitoring of pipes

Jarvis

Cawley

Nagy

2016

NDT & E International

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“…The first of these is the ratio of the skin-depth 8 to the global length scale of the perturbed field, which is given by the crack dimension l. Many studies relate specifically to thin-skin fields where 8/l << 1 and the present study is also in this context. Within the classification of thin-skin fields, widely different surface distributions can arise depending on the value of the second parameter m=l!JlrO where llr is the relative magnetic permeability of the metal specimen [ 1 ]. Values of m vary from very small to very large depending on the material properties and the operating frequency.…”

Section: Introductionmentioning

confidence: 99%