The invention discloses a
tomography method for a circular bottom plate structure of a large
storage tank, which is characterized in that air
coupling transducers which are arranged along the circumference of a bottom plate of a
storage tank at equal angular distances are used for collecting lamb wave signals, so that the defects of
corrosion, rusting,
pressure sensitivity and the like possibly existing in a
contact type transducer due to the use of a
coupling agent are avoided; by setting the included angle between the surface of the air
coupling transducer and the surface of a detection workpiece,
travel time information of a lamb wave single mode is obtained, and the difficulty of single mode
signal extraction caused by
frequency dispersion characteristics of the lamb wave is avoided; and an equal-angular-distance differential filtering
back projection algorithm suitable for the circular bottom plate is derived, and the Lamb wave
travel time information is subjected to differential,filtering and
back projection operations in sequence to obtain the
tomographic image of the circular
storage tank bottom plate structure. The method has the advantages of the wide detection object range, the high reconstruction speed, convenience in use, the accurate defect positioning and the like, and a method support is provided for detecting defects, particularly
corrosion defects, of the circular storage tank bottom plate structure.