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Technical Discussions
Jeff
NDT Inspector
Nucor Steel, USA, Joined Apr 2005, 6

Jeff

NDT Inspector
Nucor Steel,
USA,
Joined Apr 2005
6
01:54 Aug-10-2004
Surface waves

I work for a steel company. They want to know if I can inspect steel plate for cracks running transverse along the plate surface. One problem scale is on the surface. I was wondering if surface waves would penetrate the scale and give me the surface indications I am looking for. These defects are not very deep. Our customers are finding these defcts after the scale is blown off. If uktrasound is not the answer give me some ideas. I have already kicked around MT and PT butspeed is not in their favor.

Jeff Medford


    
 
 
Guest
Guest
03:26 Aug-10-2004
Re: Surface waves
Try the ACFM (Alternating Current Field Measurement) technique for detection.
----------- Start Original Message -----------
: I work for a steel company. They want to know if I can inspect steel plate for cracks running transverse along the plate surface. One problem scale is on the surface. I was wondering if surface waves would penetrate the scale and give me the surface indications I am looking for. These defects are not very deep. Our customers are finding these defcts after the scale is blown off. If uktrasound is not the answer give me some ideas. I have already kicked around MT and PT butspeed is not in their favor.
: Jeff Medford
------------ End Original Message ------------




    
 
 
Christopher Dragan
Engineering
ITWL, Poland, Joined Nov 2002, 3

Christopher Dragan

Engineering
ITWL,
Poland,
Joined Nov 2002
3
07:53 Aug-11-2004
Re: Surface waves
How deep this cracks are? If they are limited to 3 - 4 mm you can succesfully use eddy current technique. If this cracks running along plate surface that should be quite good visible.


    
 
 
Godfrey Hands
Engineering,
PRI Nadcap, United Kingdom, Joined Nov 1998, 286

Godfrey Hands

Engineering,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
286
09:51 Aug-11-2004
Re: Surface waves
----------- Start Original Message -----------
: I work for a steel company. They want to know if I can inspect steel plate for cracks running transverse along the plate surface. One problem scale is on the surface. I was wondering if surface waves would penetrate the scale and give me the surface indications I am looking for. These defects are not very deep. Our customers are finding these defcts after the scale is blown off. If uktrasound is not the answer give me some ideas. I have already kicked around MT and PT butspeed is not in their favor.
: Jeff Medford
------------ End Original Message ------------

Jeff,
Surface waves should propagate underneath a layer of scale, but cannot be generated through them with conventional contact or immersion techniques using piezo transducers.
In immersion, the surface wave will continuously "leak" back out into the couplant liquid (water) and become very inefficient.

If the waves could be generated at the sides of dry plates, they could potentially propagate right across the plates if the frequency is low enough.

Another method using surface waves is to generate the surface wave using the EMAT technique, where the sound pulse is generated on the surface of the plate through the scale. Not many NDT companies are dong this however.

What depth of crack are you looking for?

Godfrey Hands




    
 
 

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