Time efficient auto-focussing algorithms for ultrasonic inspection of dual-layered media using Full Matrix Capture

This paper describesa number ofmethods for calculating the point of incidence at a planarrefractive interface between dual-layered media for ultrasonic applications in the field of non-destructive testing. It is shown how Snell's law may be expressed as a quartic polynomial, and solved using analytical or numerical techniques to find the point of incidence at the refractive interface. An array transducer mounted onto a Perspex wedge is used to generate ultrasonic imagery of a double ‘v’ butt weld in a low carbon steel plate, using the Full Matrix Capture technique. Curve-fitting algorithms are also presented that allowautomated focussingthrough the wedge-plate interface. Finally, a description is given on how algorithms may be adapted to allow auto-focussing through dual media with a non-planar interface.