Multiskip echoes in cylindrical specimen

For accessibility reasons, some areas of a specimen should be inspected with an ultrasonic beam having undergone several successive skips on the bottom and the surface of the specimen. This allows to reach areas far from the probe . To achieve these "multiskips " controls, a 45° shear wave beam is used to prevent conversion modes that would lead to numerous echoes complicating results interpretation. Surface or backwall breaking notches can be detected with T45° mode after several skips.

CIVA's predictions for the multiskips echoes of  vertical or tilted notches have already been evaluated in a flat piece with T45° mode (see here). Here we present a study of multiskips echoes of a vertical notch located in a cylindrical specimen. The cylinder was inspected on the outside with T mode. In order to evaluate the effects of backwall  and surface curvature of the specimen on the multiple echoes of the notch, the results of the cylindrical mock-up inspection were compared with those of a planar specimen having the same thickness and inspected also in T mode. Then, to evaluate the predictions CIVA for multiskips echoes in the cylinder, the experimental results are compared to the ones simulated with CIVA. The probe used is a flat 12.7mm diameter transducer of 5MHz central frequency.


Experimental and simulation setups

Measurement of the attenuation

Notch: results obtained with the flat specimen

Notch: results obtained with the cylindrical specimen

Notch: interpretation of the comparison results

Side Drilled Holes: interpretation of the comparison results