High temperature ultrasonic crack monitoring using SH waves

The prototype implementation of a permanently installable high temperature crack monitoring system is described. The system uses an array of waveguides to excite shear horizontal (SH) waves on the surface of the component that is to be inspected. The waveguide is made of poorly heat conducting stainless steel so that it can sustain a large temperature gradient. This ensures that conventional piezoelectric transducers can be used at one end of the waveguide to excite ultrasonic waves while the other end is in contact with the component to be monitored which is situated in a harsh environment at elevated temperature (up to 600 °C). Different crack monitoring strategies using SH waves are discussed. Simulation and experimental results for the array prototype on notched plates are presented. Furthermore, experimental results on samples containing fatigue cracks are shown and measurement results that were collected from a notched plate in a furnace at 550 °C are also presented.

► Shear horizontal (SH) waveguides can be used for ultrasonic monitoring at high temperatures.
► SH waveguide array used for crack sizing at room temperatures.
► MTFM crack sizing technique generates a robust image of the crack.
► Presented technique tested at 550 °C in a furnace for extended periods.
► High temperature crack monitoring is possible with the presented technique.