Statistical evaluation of damage size based on amplitude mapping of damage-induced ultrasonic wavefield

The inability to statistically evaluate the damage size based on amplitude mapping has long plagued the ultrasound propagation imaging (UPI) system and related non-destructive evaluation (NDE) community. This paper proposes a damage visualization method called the Statistically Thresholded Anomaly Mapping (STAM) method to solve this problem. It could isolate the damage-induced anomalous waves from an ultrasonic full wavefield data, map their amplitudes into an image and statistically differentiate damage from the background noise and pristine region of a specimen, without prior knowledge or reference data of the specimen being inspected. The proposed method was demonstrated through the visualization and evaluation of a thermal damage inflicted in a glass fibre reinforced composite specimen. The effects of two parameters on result quality and accuracy of damage size evaluation were studied by varying their values independently. The optimized result showed that 99.9% of the background noises could be removed while maintaining clear visualization of damage, hence allowing the users to evaluate the presence, location, shape, size and severity of the damage accurately.