Measurement of Material Constants for the Surface Impedance Boundary Condition
Is Version Of
Begun in 1973, the Review of Progress in Quantitative Nondestructive Evaluation (QNDE) is the premier international NDE meeting designed to provide an interface between research and early engineering through the presentation of current ideas and results focused on facilitating a rapid transfer to engineering development.
This site provides free, public access to papers presented at the annual QNDE conference between 1983 and 1999, and abstracts for papers presented at the conference since 2001.
The alternating current field measurement (acfm) technique of crack detection and measurement in metals is described elsewhere in these proceedings by Lugg  and by Dover . In common with many eddy-current crack inspection probes, acfm probes are usually operated at a frequency f such that the electromagnetic skin-depth (1) δ=(μ,μ0σπf)−1/2 is much smaller than the depth of a significant crack. In this formula μr is the relative magnetic permeability of the test piece and σ its electric conductivity. Such thin-skin fields near a surface-breaking fatigue crack, with a uniform incident field, have been calculated by using a modified surface impedance boundary condition which includes a line source of magnetic flux to model the effect of the crack , .