Lift-off effect in high-frequency eddy current conductivity spectroscopy

Abu-Nabah, Bassam A.; Nagy, Péter B.

doi:10.1016/j.ndteint.2007.06.001

Cited by 36 publications

(17 citation statements)

References 17 publications

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“…Therefore, we cannot fully reconstruct the critical near-surface part of the residual stress profile in moderately peened components using only typical inspection frequencies below 10 MHz. In such cases, special high-frequency inspection techniques are needed to extend the frequency range up to 50-80 MHz, i.e., beyond the range of commercially available instruments [22][23][24][25][26].…”

Section: Eddy Current Conductivity Spectroscopymentioning

confidence: 99%

“…A recent paper by the authors reviewed four previously unreported experimental observations of anomalous materials behavior and proposed further research efforts to better understand the underlying physical mechanisms and to mitigate the adverse influence of these [25]. The most important case of apparently anomalous behavior was observed in precipitation-hardened IN718 material that is very different from those of the commercial versions reported in the literature [15,[18][19][20][21][22][23][24]. Figure 3 shows typical AECC spectra measured in (a) annealed IN718, (b) precipitation-hardened IN718, and (c) Ti-6Al-4V specimens shot-peened to different intensities.…”

Section: Eddy Current Conductivity Spectroscopymentioning

confidence: 99%

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The Effect of Hardness on Eddy Current Residual Stress Profiling in Shot-Peened Nickel Alloys

et al. 2010

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Recent research results indicate that eddy current conductivity measurements can be exploited for nondestructive evaluation of subsurface residual stresses in surfacetreated nickel-base superalloy components. According to this approach, first the depth-dependent electric conductivity profile is calculated from the measured frequency-dependent apparent eddy current conductivity spectrum. Then, the residual stress depth profile is calculated from the conductivity profile based on the piezoresistivity coefficient of the material, which is determined separately from calibration measurements using known external applied stresses. This paper presents new results that indicate that in some popular nickel-base superalloys the relationship between the electric conductivity profile and the sought residual stress profile is more tenuous than previously thought. It is shown that in delta-processed IN718 the relationship is very sensitive to the state of precipitation hardening and, if left uncorrected, could render the eddy current technique unsuitable for residual stress profiling in components of 36 HRC or harder, i.e.,

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Section: Eddy Current Conductivity Spectroscopymentioning

confidence: 99%

Section: Eddy Current Conductivity Spectroscopymentioning

confidence: 99%

The Effect of Hardness on Eddy Current Residual Stress Profiling in Shot-Peened Nickel Alloys

et al. 2010

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“…Residual stress assessment is important because there is mounting evidence that it is not possible to reliably and accurately predict the remaining service life of such components without properly accounting for the presence of residual stresses. Eddy current conductivity spectroscopy has emerged as the most promising approach for residual stress monitoring in surface-treated precipitation hardened nickel-base superalloys [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] . Unfortunately, cold work exerts a rather convoluted effect on (6) residual stress profiling in shot-peened components by eddy current spectroscopic measurements.…”

Section: Uniquenessmentioning

confidence: 99%

Non-destructive methods for materials' state awareness monitoring

Nagy¹

2010

Insight - Non-Destructive Testing and Condition Monitoring

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Electromagnetic, thermoelectric and other non-destructive evaluation methods offer unique opportunities for materials' state awareness monitoring. A variety of sensors can be built based on these principles to detect and quantitatively characterise subtle environmentally-assisted and/or service-related changes in the state of metals, such as microstructural evolution, phase transformation, plastic deformation, hardening, residual stress relaxation, increasing dislocation density, etc. In most cases, the detection sensitivity is sufficiently high for the purposes of materials' state awareness monitoring and the feasibility of the sensing method is mainly determined by its selectivity, or the lack of it, to a particular type of damage mechanism. This paper reviews recent developments in electromagnetic and thermoelectric materials characterisation and offers a feasibility assessment of these non-destructive methods through a couple of representative examples of broad interest.

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“…An example are eddy current measurements on samples that are treated by different temperatures, which generates different states of hardness and grain sizes and can be characterized by changing of the eddy current conductivity [4,6]. By measuring changes in the resistance and inductive reactance as a complex impedance of the coil, information can be gathered about the tested material.…”

Section: Theorymentioning

confidence: 99%

Sub Surface Material Characterization using High Frequency Eddy Current Spectroscopy

Heuer¹,

Hillmann²,

Klein³

et al. 2009

MRS Proc.

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New processes introduced by nano science into much more conventional industrial applications require fast, robust and economical reasonable inspection methods for process control and quality assurance. Developed for semiconductor industries the methods available for thin film characterization and quality control are often complex and require highly skilled operation personnel. This paper presents a new concept based on high frequency eddy current spectroscopy that allows reliable and robust thickness measurements of thin conducting films on silicon or insulation substrates with a thickness resolution of about 2.5 nm. The transmission mode sensor configuration is a more practical method for inline-monitoring of thin film characterization. Due to the insensitivity of the transmission mode to dislocations or slight tilting of the sample the high frequency eddy current method is a practical method for thin film characterization in the industrial environment.

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Lift-off effect in high-frequency eddy current conductivity spectroscopy

Cited by 36 publications

References 17 publications

The Effect of Hardness on Eddy Current Residual Stress Profiling in Shot-Peened Nickel Alloys

The Effect of Hardness on Eddy Current Residual Stress Profiling in Shot-Peened Nickel Alloys

Non-destructive methods for materials' state awareness monitoring

Sub Surface Material Characterization using High Frequency Eddy Current Spectroscopy

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