M2M ndt phased array for non destructive testing NDT
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Time of flight diffraction (TOFD)

The TOFD (time of flight diffraction) is a conventional NDT method.

The TOFD method typically uses a pair of conventional probes located on each side of a zone of interest (weld) (see pictures below). The probes are mounted on a scanning device that maintain a constant distance between the two probes.

TOFD inspection uses the “lateral wave echo” directly traveling from one probe to the user as reference for the surface, and the back-wall echo, indirectly traveling from one probe to the other via reflection off the back-wall, as reference for the back-wall.

On a “defect free” specimen, no indications above a selected threshold should be present in between these two echoes. On a “flawed” specimen, the TOFD inspection should show indications in between the lateral wave and the back-wall echoes.