SPECIMEN

A flat plate in inconel, 1.55 mm thickness, is inspected by a 90° tilted coil relatively to its surface, as shown on the figure below. The plate material, the inconel, has a conductivity of 1.02 MS.m-1 and a relative permeability of 1.

Plate inspected with a 90° tilted coil

probe

The probe is made out of a cylindrical coil at double function which geometrical properties are gathered on the figure below that shows the panel in CIVA allowing the definition of those properties. The acquisition is done at 100 kHz, with 1 mA in injection and reception in absolute mode.

Geometrical properties of the probe

flaw

The plate has a surface emerging notch, of 1.24 mm thickness, so non-through notch, and of 7 mm lentgh, as drawn on figure below.

Rectangular flaw

EXPERIMENT/SIMULATION COMPARISONS

The experimental measurements have been realized with an impedancemeter, it has also not been necessary to calibrate the results before the comparison.

The figure below represents the C-scans obtained with the experiment and CIVA. They look similar.

Experimental C-scans (top) and obtained with CIVA (bottom) of real part (left) and imaginary part (right)

Lissajous curves have been plotted and amplitudes, phases, real and imaginary parts as a function of the scanning are compared on the figures below. A good agreement is observed between experiments and simulations.

Lissajous curves in impedance plane, horizontal cut (left) and vertical cut (right)

Amplitude curves comparisons (top), phases curves comparisons (bottom), horizontal (left) and vertical (right) cuts.

Real curves comparisons (top), imaginary curves comparisons (bottom), horizontal (left) and vertical (right) cuts.

Finally, the table below gathers ampltudes and phases values and confirms the very low gap between experiment and simulation, less than 1 dB.

Maximal amplitudes values and corresponding phases, and discrepancies between CIVA and experiment (references: experimental values). 

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