Papers by Keyword: Guided Wave Ultrasonics

Abstract: An approach to identify damages in materials particularly aerospace composites has been developed based on application of wavelet analysis on guided wave transient signals. The wave response was convoluted against a suitable wavelet to present information in the time-frequency domain for baseline comparison of signals. By evaluating the time-frequency conditional moment, sensitive indices were computed to identify the presence of damage. Normalisation of these indices was found to be an important procedure to reduce measurement discrepancies from baseline comparison. Extending this further was the correlation of these parameters to pulse propagation time from actuator to sensor positions to generate a tomographic representation of the damage in the scanned material. These damage evaluation processes were investigated in an ultrasonic health monitoring system inspecting carbon fibre reinforced composite panels with simulated delamination. The imaging results displayed positive damage characterisation capabilities for implementation within the methodology of smart or intelligent materials.

Abstract: In this research, an advanced signal processing technique using wavelet analysis has been developed for a guided wave structural health monitoring system. The approach was applied for the detection of delamination in carbon fibre reinforced composites. A monolithic piezoceramic actuator was attached to a laminate plate for wave generation while laser vibrometry was used to facilitate the measurements of the wave response in a sensor network. This database of wave response was then processed using the continuous wavelet transform to obtain the positional frequency content. Transforms between damaged and undamaged states were compared to ascertain the presence of defects by evaluating the total energy of the time-frequency density function. Results show high damage detection indices depending on the location of the sensor and normalisation factor applied while there are positive indications that this methodology can be extended for damage characterisation.