UT - Geometrical echoes: Surface and multiple backwall echoes

The surface and several backwall echoes have been evaluated for 2 single element probes, of 6.35 mm and 19 mm diameter, and for a linear phased array probe.


Ø Crystal (mm) Mode Frequency (MHz) Bandwith (%) Phase (°)
6.35 L0° 2.25 64 340
19 L0° 2 60 0
Linear(64 elts) L, 0° to 2° 3 90 310


Two rectangular blocks of 5 mm and 20 mm thickness have been used in the study of multiple backwall echoes. Measurements and simulations have been carried out with 20 mm and 100 mm water path for a single element probe, 25 mm and 50 mm water path for a tilted phased-array probe from 0° to 2°. The probe aperture, the water path, the incidence angle and the specimen thickness are also varied.


6.35 mm transducer, 2 MHz, L0°

19 mm transducer, 2 MHz, L0°

Linear array, 3 MHz, null delay laws


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