A simple numerical model of the apparent loss of eddy current conductivity due to surface roughness

High-frequency eddy current conductivity spectroscopy for residual stress profiling in surface-treated nickel-base superalloys

“…From the point of view of nondestructive residual stress assessment, it is also very promising that the excess AECC completely vanishes upon full thermal relaxation (empty symbols) in spite of the fact that some remnant cold work is still present in the specimens. These results also illustrate that, as expected, in nickel-base superalloys the slight surface roughness produced by SP does not cause a perceivable drop of AECC up to at least 10 MHz [17,[19][20][21][22][23].…”

“…In addition, because of their significant hardness, shot-peened nickel-base superalloy components exhibit only rather limited surface roughness (E2-3 mm rms), therefore the influence of geometrical irregularities is also limited. Still, as the inspection frequency increases, the eddy current loop becomes squeezed closer to the rough surface, which creates a more tortuous, therefore longer, path and might lead to a perceivable drop of AECC [19][20][21][22].…”

The influence of substrate surface roughness on microstrip transmission line loss using conventional analyses and length‐scale fractal analysis

“…The conductor-ceramic interface will cause the electrical signal to travel a longer path following the contour of the ceramic at GHz frequencies, this has been pointed out in previous studies. [5,15,16] The printed conductor is thinner at the edges of the print; this topography is noted as the conductor edge angle. A large amount of conductor loss occurs at the edges [17] because current density increases at a conductor edge becoming larger as the corner gets sharper.…”

Iterative inversion method for eddy current profiling of near-surface residual stress in surface-treated metals

“…It is important to point out that this approximate analytical technique does not require having two calibration blocks of known conductivity to determine the frequency-dependent AECC since the effects of probe size and shape are inherently neglected. Under certain conditions, e.g., in the case of apparent conductivity increase due to near-surface compressive residual stresses [10,16] or apparent conductivity loss due to surface roughness [13,14], it becomes advantageous to evaluate the AECC as a function of frequency instead of just the complex coil impedance.…”

“…In most metals, the stress-related electric conductivity variation is quite weak and rather difficult to separate from parallel electric conductivity and, in certain cases, magnetic permeability variations caused by cold-work. In addition, surface roughness can also cause a perceivable loss of AECC at high inspection frequencies when the eddy current has to follow a tortuous path to stay within the shallow electromagnetic skin depth of the material [12][13][14].…”