Total Internal Reflection Ultrasonic Sensor for Detection of Subsurface Flaws: Research into Underlying Physics.

摘要

The report presents results of the research aimed at advancing the understanding of underlying physics and operational functionality of the Total Internal Reflection Ultrasonic Sensor (TIRUS). Propagation and reflection of ultrasonic beams in its body, which is a strongly anisotropic TeO2 crystal, were studied theoretically and experimentally. Its insertion losses that are operational characteristics of the sensor were measured using continuous wave and time-gated (pulse) techniques. It has been shown that a probable reason for their high value is the transduction loss of the transducer but not conversion of a probing shear wave into other acoustic modes. The sensor capability of sensing subsurface flaws has been proved when the sensor was in direct contact with a tested specimen. In the case of a couplant between those, its operational capability has to be proved yet. In optical experiments, the structure of ultrasonic beams has been observed for the first time from the direction forbidden for acousto-optic interaction. Two effects were discovered that have apparently never been observed before, conversion of the shear horizontal wave into a longitudinal one on its normal reflection from a free flat surface and a displacement of an ultrasonic beam on its oblique reflection from such one.