UT - Multiple echoes: Results for the 5 MHz single element probe generating P45° waves

The figure below presents an example of experimental Bscan of a vertical notch. In this example, 4 different echoes can be distinguished : a diffraction echo from the top of the notch (P direct echo) and 3 corner echoes from the bottom of the notch (P corner echo, Mixed corner echo and SV corner echo). At the bottom of the figure, on the left is shown a C-scan limited around the P corner echo (echo of interest). The echodynamic curve shows the differences in amplitude which are obtained on the whole extension of the notch. The difference is 0.5 dB maximum.

 

 

The figure below shows the comparison of experimental and simulated Bscans when the notch tilt is 0°.

 

 

CIVA diffraction echo is weaker than the corner echo. However, experimental results show that both echoes have quite similar amplitude. This difference is probably due to the notch aperture which is not taken into account in CIVA. This study focuses on corner echoes and it is not necessary to account for notch aperture to simulate them.

There is a good agreement between experimental and simulated Ascan and echodynamic curves.

 

 

Results of opened tilt angle notches (0° to 20°) inspection are presented in this section. The figure below compares experimental and simulated Bscans.

 

 

Simulated echoes look like real ones. The amplitude of the P corner echo does not change with the tilt angle. This behavior is well predicted by CIVA 11.

Experimental and simulated Ascan shape and amplitude of the P corner echo for all tilt angles are in good agreement.

 

 

The figure below show variation of experimental and simulated P corner echoes amplitude with the tilt angle. Whatever the tilt angle, simulation results and experiment are in good agreement (less than 2 dB difference). A measure of reproducibility is presented in black dots. The experimental error is less than 1 dB.

 

 

Results of closed tilt angle notches (-20° to 0°) inspection are presented in this section. The figure below compares experimental and simulated Bscans.

 

 

Simulated and experimental echoes are in good agreement. The P corner echo amplitude almost does not change with the tilt angle. This behavior is well predicted by CIVA.

Furthermore, the shape of P experimental and simulated corner echoes are in good agreement.

 

 

Inspection of backwall breaking notches in a 5 mm depth planar specimen were performed with a 5 MHz immersion probe. The incidence angle of the probe was chosen in order to generate P45° waves in the mock-up.

P45° inspections show that experimental corner echoes amplitude are in good agreement with CIVA 11 predictions. There are differences on the diffraction echo because the notch aperture was not taken into account. This validation study does not focus on this echo, so these differences are not studied here.