FURTHER STEP INTO THE DIFFRACTION PHENOMENA TO ADVANCE IN SIZING AND CHARACTERIZATION OF FLAWS IN WELDS DETECTED BY PULSE ECHO, PHASED ARRAY AND TOFD.

Speaker:
NARDONI, GIUSEPPE; I&T NARDONI INSTITUTE; Italy

Authors:
Nardoni, G.; I&T Nardoni Istitute; Italy
Nardoni, D.; I&T Nardoni Istitute; Italy
Nardoni, P.; I&T Nardoni Istitute; Italy
Dorise, A.; INSA Centre Val de Loire; France
Danelutti, J.; INSA Centre Val de Loire; France

ID: ECNDT-0201-2018
Session: Ultrasonic Inspection 1
Room: G2
Date: 2018-06-13
Time: 10:00 - 10:20

Diffraction is becoming a key phenomena for the characterization and sizing of planar indications in welds as requested by ASME code and EN code.
The paper is divided in two steps: the first step analyses the reflection/diffraction from planar flaws with angles of 60°, 70° and 45°.
The conclusion of this first step was that the detection with 60° and 70° is based on reflection of the surface; for 45° angle beam the detection is based on diffraction from the tips with a difference of 10-12 dB with respect to the same calibration on a side drilled hole of 3 mm.
The second step has been focused to optimize the angle at which diffraction gives the best results in terms of resolution of the two tips of the planar flaws.
In this stage the diffraction factor has been determined. This factor takes in consideration amplitude, noise level, resolution of the signal in A scan presentation.
The best diffraction angle with shear waves is 28°.
Along the research it has been also verified the criteria of defect characterization among planar and volumetric flaws in the norm EN 23279.
The 9 dB criteria is not applied between angles of 60° and 70°; it is valid only for 45° angle beam with respect to 60° and 70°.
At the end of this research program an improved procedure for characterization and sizing defect in weld examination using TOFD, Phased Array and Pulse Echo has been reached.