The detection of flaws in austenitic welds using the decomposition of the time-reversal operator.
The non-destructive testing of austenitic welds using ultrasound plays an important role in the assessment of the structural integrity of safety critical structures. The internal microstructure of these welds is highly scattering and can lead to the obscuration of defects when investigated by traditional imaging algorithms. This paper proposes an alternative objective method for the detection of flaws embedded in austenitic welds based on the singular value decomposition of the time-frequency domain response matrices. The distribution of the singular values is examined in the cases where a flaw exists and where there is no flaw present. A lower threshold on the singular values, specific to austenitic welds, is derived which, when exceeded, indicates the presence of a flaw. The detection criterion is successfully implemented on both synthetic and experimental data. The datasets arising from welds containing a flaw are further interrogated using the decomposition of the time-reversal operator (DORT) method and the total focusing method (TFM), and it is shown that images constructed via the DORT algorithm typically exhibit a higher signal-to-noise ratio than those constructed by the TFM algorithm.
Department of Mathematics and Statistics , University of Strathclyde , Glasgow G1 1XH, UK.
Laura J
LJ
Cunningham
Department of Mathematics and Statistics , University of Strathclyde , Glasgow G1 1XH, UK.
Anthony J
AJ
Mulholland
Department of Mathematics and Statistics , University of Strathclyde , Glasgow G1 1XH, UK.
Katherine M M
0000-0003-4345-7054
KM
Tant
Centre for Ultrasonic Engineering , University of Strathclyde , Glasgow G1 1XW, UK.
Anthony
A
Gachagan
PZFlex Europe , 50 Richmond Street , Glasgow G1 1XP, UK.
Gerry
G
Harvey
Doosan Babcock, T&E Building , Porterfield Road, Renfrew, Glasgow PA4 8DJ, UK.
Colin
C
Bird
arrays; imaging; non-destructive testing; time reversal; ultrasonics