![]() ![]() This round trip signal is also known as a '30-70-70' signal to denote the angle of each portion of the triangular soundpath. The 'mode-converted' 70 deg wave will strike the reflector face and then propagate back to the transducer. The 30 deg shear wave will hit the back surface of the test piece and some of the wave energy will be reflected as a 70 deg longitudinal signal. ![]() Shear Wave (30-70-70): Along with the 70 deg longitudinal wave, a 30 deg shear wave is generated. The behavior of each of these components can be broken down into the following three categories:ĭirect Longitudinal Wave: This is the 70 deg refracted longitudinal wave, which after a quick and easy calibration procedure, should only appear when a crack is very deep. These different modes all interact to create a unique echo pattern which will vary depending upon how far into the material the defect has propagated. ![]() As a result of the incident angle used in creating this 70 deg longitudinal wave, other wave modes are created. The single element transducers used in the ID creeping wave technique are designed to create a 70 deg refracted longitudinal wave in the material of interest. More About the Single Element Creeping Wave Transducer This technique continues to grow in popularity because of simplicity and because it can provide both detection and preliminary sizing information about the suspected flaw. Further evaluation of signal amplitude, rise and fall time, echo dynamic and pulse duration, hopefully will help determine if the suspect signal is from ID geometry, counter bore, root, or if it is an actual flaw.Īnother method that can be used for the qualification process involves the use of a single element creeping wave transducer. This initial process usually involves the use of the same 1.5, 2.25, or 5MHz shear wave angle beam transducer that was used in the detection phases. Once a suspected Inner-Diameter (ID) connected crack has been detected by general code or regulatory mandates, it then must be qualified. In general, these techniques have found application for the detection, characterization and sizing of intergranular or transgranular stress corrosion cracks and fatigue-type cracks whether inherent, processing or service induced. This paper provides a brief summary of advanced detection and sizing techniques for the evaluation of flaws connected to the inner surface of test material. ![]()
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