Re: curved probes in ToFD ----------- Start Original Message -----------
: what is the criteria for choice of curved probes in TOFD?
------------ End Original Message ------------
In addition to the reply of Ed Ginzel with respect to the referenced standards:
Use of time-of-flight diffraction technique (TOFD) for testing of welds
in 7.2.2 asks for the matching of probes according to EN 1714.
EN 1714:1997 (2002)
Ultrasonic testing of welded joints
in 6.3.3 gives the equation referenced by Ed Ginzel.
But this equation is not correct.
EN 1417 is under revision now and will be published again soon.
The correct equation (when the max gap is smaller than 0.5 mm, which can be tolerated for 4 MHz), is
Dobj < (D)squared/ 2 mm,
where Dobj is the outer diameter of the object, and D is the dimension of the transducer parallel to the curvature.
The same correction has to be made to the respective equations in 3.4.1 and 3.4.2 of
Ultrasonic testing - Part 2: Sensitivity and range setting
(The above equation with squared transducer diameter is correct)
GE Inspection Technologies GmbH
Chairman of CEN/TC121/SC5/WG2 (UT of welds)
Chairman of CEN/TC138/WG2 (UT)