SLIC
Shear and Longitudinal IGSCC Characterisation or Simultaneous use of Shear and Longitudinal waves to Inspect and Characterise Cracks
SLIC – Shear and Longitudinal IGSCC Characterisation or Simultaneous use of Shear and Longitudinal waves to Inspect and Characterise Cracks – was developed in the 1980s by Southwest Research Institute (SwRI) to overcome problems associated with through-wall sizing of cracks under-cladding in reactor pressure vessels and subsequently used for cracks in austenitic welds.
The probes used for the SLIC technique are similar to the TRL probe described last month except that the two piezoelectric crystals are placed in a 'fore and aft' tandem configuration in the same probe body.
The rear crystal transmits both a high angle longitudinal wave beam and the associated shear wave beam. The front crystal receives reflected and mode converted signals of one or both wave modes depending on the configuration. The technique measures the time delay between associated received signals (referred to as a doublet if two received signals or a triplet if three) to size cracks in the through-wall direction.
A unique feature of the SLIC system is that the distance between the doublet/triplet signals is practically independent of the position of the sensor. The probes come in different configurations: SLIC-30, SLIC-40 & SLIC-50.
Because the crystals in the SLIC probe are configured in a fore-and-aft arrangement and not side-by-side like the twin-crystal TRL probes, the probe has a narrower body, which is advantageous for more accurate length sizing.
For more information on SLIC probes see:
http://www.ndt.net/article/0198/wues_lim/wues_lim.htm
What the hec?! articles are not intended to be the definitive account on the topic or acronym in question. Readers’ comments and contributions are welcomed. Email: ndtnews@bindt.org
The probes used for the SLIC technique are similar to the TRL probe described last month except that the two piezoelectric crystals are placed in a 'fore and aft' tandem configuration in the same probe body.
The rear crystal transmits both a high angle longitudinal wave beam and the associated shear wave beam. The front crystal receives reflected and mode converted signals of one or both wave modes depending on the configuration. The technique measures the time delay between associated received signals (referred to as a doublet if two received signals or a triplet if three) to size cracks in the through-wall direction.
A unique feature of the SLIC system is that the distance between the doublet/triplet signals is practically independent of the position of the sensor. The probes come in different configurations: SLIC-30, SLIC-40 & SLIC-50.
Because the crystals in the SLIC probe are configured in a fore-and-aft arrangement and not side-by-side like the twin-crystal TRL probes, the probe has a narrower body, which is advantageous for more accurate length sizing.
For more information on SLIC probes see:
http://www.ndt.net/article/0198/wues_lim/wues_lim.htm
What the hec?! articles are not intended to be the definitive account on the topic or acronym in question. Readers’ comments and contributions are welcomed. Email: ndtnews@bindt.org
