08:18 Aug-19-2007 Ed Ginzel R & D, - Materials Research Institute, Canada, Joined Nov 1998 1185
Schlieren visualisation of headwaves?
The ASTM Standard E-2192 is an excellent description of several ultrasonic methods of sizing surface connected flaws. The document had a long history of development and I was only the last of several people that helped to get it into a published format. The final version is noted as having significant input from the Electric Power Research Institute (EPRI). Note # 2 states "This Standard Guide is adapted from material supplied toASTM Subcommittee E07.06 by the Electric Power Research Institute (EPRI)".
One of the statements made in the EPRI notes includes, "The existence of the indirect shear wave, headwave, has also been proven experimentally by Schlieren optics".
For years I tried to visualise the shear mode by schlieren but was unable. I was only able to do so using photoelastic methods. I have sent emails to EPRI asking for verification of this statement but no reply has been provided. Does anyone have a definitive example of this "schlieren" demonstration of shear mode or is it as I suspect a mis-identification of technique and "photoelastic" should have been the term used instead of "schlieren"?