Enhanced Damage Characterization using Wavefield Imaging Methods

Wavefield imaging methods are becoming a popular tool for characterizing and studying elastic field interactions in a wide variety of material systems. By using a scanning laser vibrometry detection system, the transient displacement fields generated by an ultrasonic source can be visualized and studied in detail. As a tool for quantitative nondestructive evaluation, the visualization of elastic waves provides a unique opportunity for understanding the scattering of elastic waves from insipient damage, where the detection and characterization of damage features using ultrasound can be enhanced in many instances [1-3]. In the present effort, the detection and direct imaging of fatigue cracks in metals, and delaminations in composites, are described. An examination of the transient displacement fields near the scattering sites showed additional details related to the local damage morphology, which can be difficult to account for using traditional NDE sensing methods. A combination of forward models and experimental wavefield imaging was subsequently used to understand the impact of local near-field scattering processes on the pulse-echo detection of far-field signals in a traditional ultrasound sensing measurement