wave that travels near surface (called “lateral wave”). Red signals are from diffracted waves (from bottom and top crack tips). Green signal comes from ultrasound backwall reflection.
Figure 9 – TOFD theory on weld inspection. Main signals.
The collection of several A-scans, each one obtained from each point in a probe pair scanning position, gives an bi-dimensional image from the weld seam containing defects (figures 10 and 11).