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TEAM Workshop Problem 8 -
Coil Above A Crack
Gallery spotlightSensors & NDT
In this example, MagNet is used to deal with a non-destructive testing (NDT) problem with eddy currents. TEAM Problem 8, "Coil Above a Crack: A Problem in Non-Destructive Testing" defines an austenitic stainless steel block containing a rectangular flaw (a crack). A probe consisting of one inducing solenoid and two receptive solenoids is moved across the surface of the block. The objective is to detect the crack by measuring the difference of magnetic fluxes through the two solenoids.
Using MagNet's Time Harmonic solver, the induced eddy currents are accurately computed. The comparison between the experimental results and the simulation results obtained from MagNet demonstrates how MagNet can be used to deal accurately with NDT problems.
METHODS and RESULTS
MAGNITUDE COMPARISONS - PARALLEL MOVING
This graph displays the magnitude of the differential magnetic flux of the two receptive solenoids when the probe is moved away from the center of the crack in a direction parallel to the crack. The experimental results from the University of Tokyo as well as the simulation results from MagNet are presented. The experimental results were given in a dimensionless form; hence, the MagNet result has been scaled to give the best fit. Note that the experimental results taken with the probe on the the left and right sides of the crack are not equal; this discrepancy is an indication of the experimental error in the Tokyo measurements.
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PHASE COMPARISONS - PARALLEL MOVING
This graph displays the phase of the differential magnetic flux of the two receptive solenoids when the probe is moved away from the center of the crack in a direction parallel to the crack. Since the experimental results were given without a phase reference, the MagNet result has been shifted to obtain the best fit.
Click to zoom
MAGNITUDE COMPARISONS - PERPENDICULAR MOVING
This graph again shows the comparison of the magnitude of the differential magnetic flux; however, in this case the probe is moving away from the flaw in a direction perpendicular to the crack instead of parallel to it.
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PHASE COMPARISONS - PERPENDICULAR MOVING
This graph shows the comparison of the phase of the differential magnetic flux when the probe is moved in a direction perpendicular to the crack.
Click to zoom
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PARALLEL MOTION
This graph shows the differential magnetic flux of the probe when moved parallel to the flaw. The data is normalized so that it matches the graph in the original TEAM 8 benchmark paper.
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PERPENDICULAR MOTION
This graph shows the differential magnetic flux of the probe when moved perpendicular to the flaw. The data is normalized so that it matches the graph in the original TEAM 8 benchmark paper.
Click to zoom
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