Piezoelectric Wafer Active Sensor Guided Wave Imaging

摘要

Active sensing methods use actuators/sensors permanently attached to the structure to generate guided waves and measure the arrival waves propagating through the structures. The damage diagnosis is performed through the examination of the arrival waves carrying structural features. Since direct sensory data in guided wave interrogation are implicit with damage related information, advanced signal processing is necessary to extract damage related features for damage diagnosis. Array signal processing is an approach that can map the structure being interrogated with propagating guided waves, producing a visual indication of damage presence, location, and size for crack damage. The arrays can be configured with sensors closely placed or spatially distributed and used in pitch-catch mode.In this paper, we first studied guided wave excitation on isotropic plates and the capability of using piezoelectric wafer active sensors to selectively excite a certain mode in the structure. Then several algorithms for imaging with different types of arrays were investigated. The algorithms were applied to isotropic specimens including thin aluminum plates with hole and crack damage, and thick steel plates with hole damage. The resolution (minimal detectable damage size) was also investigated and compared to the resolution of a linear phased array. Image post processing was used to yield an estimation of the damage size.