UT - Corner echoes with SV mode: Simultaneous influence of the notch length and the refraction angle

CONFIGURATION

In the following configuration, the specimen is a planar steel mock-up of 20 mm thickness containing 4 backwall breaking notches: 3 notches of dimensions 20×2 mm, 20×5 mm, 20×15 mm and a notch of dimensions 6×15 mm.

 

 

A Ø12.7 mm immersion probe is used in order to generate SV waves at different refraction angles with a water path of 20 mm.

 

RESULTS

Each notch is associated with a number in order to facilitate the results display:

 

Notch number 1 2 3 4
Height 2 mm 2 mm 2 mm 6 mm
Length 2 mm 5 mm 15 mm 15 mm

 

SV45 to SV65 inspections are performed with a Ø12,7 mm circular immersion probe functionning at 4.5 MHz with 20 mm water path. The input signal central frequency is 4.5 MHz, the bandwidth 73% and the phase 270°.

 

The results are calibrated relatively to a Ø2 mm SDH of 40 mm length located at 15 mm depth.

 

 
 

 

Whatever the refraction angle, there is a good agreement between experimental results and CIVA on the highest notch (6×15 mm). For the 2 mm high notches, CIVA does not predict accurately the corner echo amplitude for the 55° refraction angle, close to the 57° T-waves critical angle. The difference becomes larger as the notch length gets smaller. Except for this 55° refraction angle, the whole results globally predict a good agreement between CIVA and the experiment.

 

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