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444 views
03:09 Jan-29-2002

Massimiliano Pau

Teacher, -
Univ. of Cagliari, Dept. of Mechanical Engineering,
Italy,
Joined Sep 2002
25
Diffraction effects

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!




 
09:21 Jan-31-2002

N.T. Azarov

Engineering
GosNIIGA,
Russia,
Joined Jan 2000
12
Re: Diffraction effects -----éÓÈÏÄÎÏÅ ÓÏÏÂÝÅÎÉÅ-----
ïÔ: forum@ndt.net
ëÏÍÕ: undisclosed-recipients:;
äÁÔÁ: 29 ÑÎ×ÁÒÑ 2002 Ç. 15:13
ôÅÍÁ: Diffraction effects

> * 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:
azar@orc.ru, azar@ncplg.msk.ru
N. Azarov.
>--
.



 


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