> * This article was posted by Massimiliano Pau >Reply at:http://www.ndt.net/wshop/forum/messages/3839.htm > >Dear colleagues > >I'm trying to measure small flat-bottom holes (diameters from 0.5 to 10 mm) in a steel specimen by scanning them with a longitudinal immersion 10 MHz focussed probe. > >My question are: > >1. How diffraction effects can alter the reflection of the ultrasonic beam when part of it hits the edge of the hole? > >2. Can I take into account these effects in order to "correct" the size which comes from the C-scan results? > >3. Is there any literature reference (please not too theoretical if possible) on this topic? > >Thanks in advance > >Massimiliano Pau > >P.S. thanks to Joe Buckley for his precious advice about the noise with electromagnetic fields generated by an inverter. It worked! >
>Dear, Mr Pau. I have experience of a ultrasonic control thin-walled (0,5-5mm) of welded seams on frequencies 10-15MHz by a focusing transducer (immersion control). A diameter of a focal spot 0,5mm. C-scan the image of an imperfection (flaw) is a convolution of two functions: functions of reflection of an imperfection (flaw) (including diffractional effects) and cut of a focal spot. The dependence of sort is obtained: "conditional square - diameter of an imperfection (flaw)". My E-mail: firstname.lastname@example.org, email@example.com N. Azarov. >-- .