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Hi-Spec Systems
Hi-Spec Systems are an innovative, forward thinking and fast moving non-destructive testing (NDT) technology company who specialise in the design ...

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Technical Discussions
Nick Welland
Other, Quality and NDT
Aben Technical Services, Australia, Joined Oct 1999, 42

Nick Welland

Other, Quality and NDT
Aben Technical Services,
Australia,
Joined Oct 1999
42
09:56 Sep-15-1999
UT Bond Testing

I would appreciate suggestions on this problem. I have been requested to search for loss of bond between 4 mm carbon steel and an epoxy potting compound. Only access for a normal beam is from the steel plate face and any back echo from the (very attenuative) epoxy seems to be lost in the steel repeat echoes. I would like to be able to map any loss of bond. The only other option seems to be to grind the accessible top edge of the assembly and use LPT but I would rather this was a last resort.

Best regards

Nick Welland


    
 
 Reply 
 
Wieslaw Bicz
Wieslaw Bicz
01:28 Sep-15-1999
Re: UT Bond Testing
: I would appreciate suggestions on this problem. I have been requested to search for loss of bond between 4 mm carbon steel and an epoxy potting compound. Only access for a normal beam is from the steel plate face and any back echo from the (very attenuative) epoxy seems to be lost in the steel repeat echoes. I would like to be able to map any loss of bond. The only other option seems to be to grind the accessible top edge of the assembly and use LPT but I would rather this was a last resort.

: Best regards

: Nick Welland

It could be possible to use the C-scan method with the focused beam
and short pulse, but I think it could be much quicker and cheaper to use
the holographic method, we are using for the fingerprint testing.
If you could send us a sample, we can test it and show you the results.

Wieslaw Bicz

http://www.optel.com.pl



    
 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
05:18 Sep-15-1999
Re: UT Bond Testing

: I would appreciate suggestions on this problem. I have been requested to search for loss of bond between 4 mm carbon steel and an epoxy potting compound. Only access for a normal beam is from the steel plate face and any back echo from the (very attenuative) epoxy seems to be lost in the steel repeat echoes. I would like to be able to map any loss of bond. The only other option seems to be to grind the accessible top edge of the assembly and use LPT but I would rather this was a last resort.

One approach that often works for this sort of thing, assuming the steel is smooth and of uniform thickness, is to look at changes in the ringdown pattern of the multiple echoes from the steel wall. Try a 5 MHz or preferably 10 MHz delay line transducer with any good flaw detector. Couple to an un-bonded reference standard and observe the ringdown pattern, then couple to a bonded area. You should see the multiples drop off more quickly due to the damping effect of the epoxy.

Because of the acoustic impedance mismatch between steel and epoxy, the change in the first backwall echo between bond and disbond will be fairly small, but the effect adds up with each round trip through the steel and should be easy to see on the fourth or fifth multiple. Unfortunately, this *won't* work if the steel is rough or corroded, because then the steel conditions will introduce a greater variable to the ringdown pattern.

--Tom Nelligan


    
 
 Reply 
 
Nelly Jurova
Nelly Jurova
00:15 Sep-22-1999
Re: UT Bond Testing
: I would appreciate suggestions on this problem. I have been requested to search for loss of bond between 4 mm carbon steel and an epoxy potting compound. Only access for a normal beam is from the steel plate face and any back echo from the (very attenuative) epoxy seems to be lost in the steel repeat echoes. I would like to be able to map any loss of bond. The only other option seems to be to grind the accessible top edge of the assembly and use LPT but I would rather this was a last resort.

: Best regards

: Nick Welland


Dear Mr. Welland,
our company has a wide experience in bond testing. Please, send us a sample and we will test if our Bond Tester can help to resolve your problem .

Regards
Nelly Jurova
Votum JSC
www.votum.md


    
 
 Reply 
 

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