Angle-beam shear wave scattering from buried crack-like defects in bonded specimens

Ultrasonic wavefield imaging, which refers to the measurement of wave motion on a 2-D rectilinear grid resulting from a fixed source, has been previously applied to angle-beam shear wave propagation in simple plates with through-holes and far-surface notches. In this prior work, scattered waves were analyzed using baseline subtraction of wavefields acquired before and after a notch was introduced. In practice, however, defects of interest often occur between bonded layers and it is generally not possible to record data from the same specimen in both the undamaged and damaged states, even in the laboratory. Direct baseline subtraction of wavefields thus becomes impractical as a tool for analyzing scattering. This present work considers measurement and analysis of angle-beam waves in bonded specimens with and without buried defects originating from fastener holes. Data from fastener holes with and without simulated damage in the form of notches are compared, and it is shown that wavefield baseline subtracti...