SQUID-NDE method on damaged area and damage degree of defects in composite materials

Visualization of flowing current in braided carbon fiber reinforced plastics using SQUID gradiometer for nondestructive evaluation

“…In the case of J x distributions, white region means large current toward the +x direction. Black regions above both the samples' edges in the figures are the edge effects [7]. In the case of J y distributions, white region means current toward the +y direction, while black region means current toward the -y direction.…”

“…A planar first-order HTS-SQUID gradiometer, with small differential pickup coil and a small baseline, functions as a current detector with high spatial resolution when a liftoff between the gradiometer and a conductive panel sample is short enough such that the liftoff is comparable to the baseline, as described elsewhere [7]. In this study, we put electrical terminals on both ends of each sample to induce an ac current in the longitudinal direction, while applying an ac voltage across each sample.…”

“…When such a sample, in which an ac current is being induced, is set on the x-y plane, the induced current densities J x and J y in the sample have similar distributions as the magnetic field gradients dB z /dy and -dB z /dx in an x-y plane near the sample. These relationships  0 J x ≈ dB z /dy, and  0 J y ≈ -dB z /dx, between the currents and the field gradients, can be derived from the Maxwell's equation,   H = J [7]. Based on this principle, we employed a SQUID-NDE system using a small HTS-SQUID gradiometer and an automated xy-stage, whose details were described elsewhere [6].…”

“…The measured area above the samples was the area shown in the photographs in Figures 2 and 3. We converted the field gradient distributions of dB z /dy and -dB z /dx into the distributions of current components J x and J y based on the field gradient to current conversion scheme [7]. In this paper, the units of the converted current distributions were shown with those of the measured field gradients dB z /dy and -dB z /dx.…”

Fabrication of Magnetometers With Multiple-SQUID Arrays

“…T HERE is great interest in using high-dc superconducting quantum interference devices (SQUIDs) for practical applications like geophysical prospecting, biomedical investigations [1], and nondestructive evaluation [2]. Magnetometers with field sensitivities below 50 at 77 K have been reported [3], [4].…”