Monitoring crack propagation in turbine blades caused by thermosonic inspection

Bolu, G. and Gachagan, A. and Pierce, G. and Harvey, G. and Choong, L.; (2010) Monitoring crack propagation in turbine blades caused by thermosonic inspection. In: REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION. American Institute of Physics, USA, p. 1654. ISBN 978-0-7354-0748-0

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Abstract

High power acoustic excitation of components during a thermosonic (or Sonic IR) inspection may further propagate existing cracks. Monitoring such changes through destructive or non-destructive means is no trivial task. Process Compensated Resonance Testing (PCRT) technology offers the capability to monitor the growth of fatigue-induced cracks (and other progressive defects) through statistical analysis of changes in a components resonant spectra over time. This technique can be used to detect changes in material properties by comparing a components spectra to itself at regular intervals after systematic exposure to high power excitation associated with thermosonic inspection. In this work, the resonant spectra of 6 cracked and 6 uncracked turbine blades are captured prior to batch of inspections. Next, these spectra are analysed using proprietary software for changes in resonant behaviour. Results from this work indicate that a typical thermosonic inspection of a turbine blade for crack detection does not cause crack propagation or degrade a blades structural integrity.