Reliable crack detection in turbine blades using thermosonics: an empirical study

Excitation generated by ultrasonic horns typically used in thermosonics (or Sonic IR) is non-reproducible, raising concerns that cracks in some locations can be missed. This paper presents an empirical study on the thermosonic inspection of turbine blades. The objective is to assess the reliability of thermosonics as an NDT screening method for findings crack in turbine blades. First, a study was carried out to establish the operating parameters that generated the highest possible temperature rise from a crack. Next, a repeatability study was conducted to measure consistency of results in 300 tests, which showed 100% repeatability. Finally, 60 cracked blades were inspected, with the known cracks in 57 blades detected. These results show the potential of thermosonics as a reliable NDT screening method for finding cracks in turbine blades