Ed Trotter
Posted:
1/13/2001 4:50:25 AM
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Email: trotteje@yahoo.com
Subject: ID Creeper
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ID creepers are very common. We have been using them since the early 80's. The idea is very simple. All transducers produce the same wave forms. The only diffrence is each type of transducer highlights a certain or many waves in the material. When utilizing refracted longitudinal waves (Below the first critical angle) you also produce a shear wave. It travels at less than half the velocity of the L-wave and therefore has less than half the angle. These transducers also produce what is kown as a head wave or frontal lobe. This travels just below the surface at a longitudinal velocity. As it travels it gives up it's energy in the form of indirect shear energy. This energy travels to the ID and reconverts back to a longitudinal wave traveling along the ID surface. If it strikes a planar reflector the process is reversed and you receive a signal. If not it also give up it's energy in the form of shearwaves until it is attenuated. Although sound waves reflect at an equal angle, they also mode convert at the same time whenever they strike a surface at an oblique angle. You can use single element transducers, dual or tandem search units. Each produces an ID creeper, but emphasizes a different waveform. ID creepers are not very effective, however unless the ID surface is parallel with the OD surface. It can produce spurious signals and me misinterpreted. Send me you email and I will send you a diagram of how one works.
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sych
Posted:
7/31/2001 10:16:28 AM
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Email: marksych@ hotmail.com
Subject: id creeper diagram request
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I have been a level 2 for a couple of years and would appreciate your info on id creeper waves .
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William Blum
Posted:
8/2/2001 11:22:02 PM
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Email: wblum@brighttechnical.com
Subject: ID Creeper Article
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Here is an article on ID creeper waves written by Mark Davis http://www.ndt.net/article/1198/davis/davis2.htm#1. You should find it very helpful.
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Information
UT - Ultrasonic Testing
