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Technical Discussions
Don
Don
05:57 Jan-04-2005
Eddy current sensors for micro defects

Has anybody any experience of using eddy currents for the detection of surface-breaking micro-defects, around 0.1mm in length. I have seen several papers discussing probe designs, but has anybody actually seen or used these in real life ?


    
 
 
Dr.Raimond Grimberg
R & D, Professor
National Institute of R&D for Technical Physics, Romania, Joined Nov 2001, 2

Dr.Raimond Grimberg

R & D, Professor
National Institute of R&D for Technical Physics,
Romania,
Joined Nov 2001
2
02:33 Jan-05-2005
Re: Eddy current sensors for micro defects
----------- Start Original Message -----------
: Has anybody any experience of using eddy currents for the detection of surface-breaking micro-defects, around 0.1mm in length. I have seen several papers discussing probe designs, but has anybody actually seen or used these in real life ?
------------ End Original Message ------------

We have a lot of experience for detecting the microcracks. we use for this, two types of probes:
- microfocussed AC transducers with orthogonal coils
- EC microsensors array and specifically algorithms for localizing the defect.
In the case in which you need details, don't hesitate to contact us.
Best regards,
Raimond Grimberg



    
 
 
Steven Plummer
Steven Plummer
01:56 Jan-18-2005
Re: Eddy current sensors for micro defects
I can see you have a knowledge of non destructive testing could you help me out with a problem. I have a 600mm diameter pressure vessel with a 8mm wall thickness. it is made from large preformed sheets which are welded together. Could anyone tell me the likely modes of failure and the ndt method which should be used? will there be any particular problems that will be encountered.

I would be grateful for your response



    
 
 
S.V.Swamy
Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex , India, Joined Feb 2001, 785

S.V.Swamy

Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex ,
India,
Joined Feb 2001
785
07:23 Jan-22-2005
Re: Eddy current sensors for micro defects
----------- Start Original Message -----------
: I can see you have a knowledge of non destructive testing could you help me out with a problem. I have a 600mm diameter pressure vessel with a 8mm wall thickness. it is made from large preformed sheets which are welded together. Could anyone tell me the likely modes of failure and the ndt method which should be used? will there be any particular problems that will be encountered.
: I would be grateful for your response
------------ End Original Message ------------
Dear Steven,

Greetings. The welds are the weakest area, assuming that the plates were ultrasonically tested for laminations before being pressed and that the pressing did not introduce deep surface cracks on the convex side (which can be checked out by dye penetrant testing and or magnetic particle testing). The welds (I am assuming they are butt welds) should have been tested using liquid penetrant test during the welding and by x-ray radiography finally.

If you are able to, you can rig up an Acoustic Emission Test with a few channels so that during pressurisation, any growing crack will set off AE alarm, so that the pressurisation can be stopped without the welds actually failing.

Best wishes.

Swamy




    
 
 

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