Abstract

Ultrasonic NDE techniques, such as time-of-flight diffraction (TOFD), have been developed using modelling and experiments, and are well understood when cracks are smooth and straight. However, in environments where there are extreme changes in temperature and pressure, as with nuclear power station components, the damage that occurs is often not uniform. Rough cracks are formed and these are much more challenging to characterise. The qualification of ultrasound inspections of defects that are expected to be rough (typically thermal fatigue or stress corrosion cracking) is presently very conservative, owing to the uncertainty of the amplitudes of rough surface reflections. Any individual rough surface is unique and so scattering signatures differ from one surface to the next. The pragmatic solution is to apply a large safety threshold on the expected reflection amplitude, but this can lead to unnecessary shut-downs and early retirement of components. An alternative approach has been developed by the authors, whereby the expected reflection from a rough defect can be predicted using a statistical model. Although every rough defect is randomly determined, it is possible to anticipate statistical metrics of a rough surface using extensive industrial databases of characterised in-service defects. Given only the angle of incidence and two statistical parameters, the expected reflection amplitude is obtained instantaneously for any scattering angle and length of defect. The method has been investigated for the scattering of both incident longitudinal and incident shear waves, and includes the subsequent mode-conversion.

How to Cite:

Haslinger, S. ., Lowe, M. ., Huthwaite, P. ., Craster, R. . & Shi, F. ., (2019) “Expected amplitudes of ultrasonic elastic waves scattered from rough defects”, Review of Progress in Quantitative Nondestructive Evaluation .