Efficient extraction of the directional wave curves from a pulsed ultrasonic polar scan experiment

The pulsed ultrasonic polar scan (UPS) technique provides an amplitude map with characteristic contours reflecting the critical bulk wave angles, which relate to the mechanical stiffness of the insonified material spot. Besides these contours, additional information is captured in a UPS experiment which has particular importance for the inspection of anisotropic materials. By extensive post-processing on a single UPS experiment, we successfully extracted (i) the critical bulk wave angles, (ii) the phase velocity profile, (iii) the slowness vector, (iv) the walk-off angles and (v) the energy velocity profile, and this for the three different polarization states of bulk waves. The procedure is demonstrated and discussed for an aluminum sample as well as an autoclave manufactured orthotropic [0]8 carbon/epoxy laminate, both having arbitrary dimensions. Comparison with numerical computations yield good agreement. It is worth noting that the carbon/epoxy laminate shows an extraordinary large walk-off angle of more than 70° for the longitudinally polarized wave