09:48 Aug-06-2000 andy cunningham Consultant, NDT/QA QC/R&D ASNT,PCN, Canada, Joined Feb 2000 14
dear sirs for the past year i have been playing with id and od creeping wave probes. i have now made a probe with a polarized shoe that creeps on the id and the od at the same time. can anyone tell me what to do with it.
02:14 Aug-07-2000 Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998 1199
Re: creeping wave Andy: I would be interested to learn more about the "polarisation shoe". The "so-called" creeping wave is putatively formed as a result of a simple compression wave interacting at a free boundary. Upon incidence from the shoe designed to provide a refracted angle somewhere between about 70-80 degrees in the solid test piece, the "creeping wave" forms on the near surface. Since the incident angle from the shoe ALSO results in an SV shear mode at a smaller angle (typically 30-35 degrees) a second mode conversion occurs on the far surface (assuming it to be parallel to the near surface). The mode converted wave is of course compression (converted from SV Shear). The angle of the converted compression wave off the far surface is similar to the initial refracted angle (between 70-80 degrees) and the same mechanics account for the initiation of the far surface "creeping wave".
These principles are well explained in a paper on dissimilar metals by Dr. Schmid (you can find it in a back issueof the NDT.net).
My point is that the Near and Far (ID and OD) creeping waves are a naturally occuring event but they could not occur at the "same" time. The near (OD?) occurs first and the far (ID?) occurs after the slower SV shear wave has impinged on the far surface.
If you meant that your probe can produce both I think you could have achieved the same results with a 70 degree L Wave probe.
: dear sirs : for the past year i have been playing with id and od creeping wave probes. : i have now made a probe with a polarized shoe that creeps on the id and the od at the same time. : can anyone tell me what to do with it.