Dual-longitudinal-mode ultrasonic testing

DETAILED DESCRIPTION In accordance with the present invention, an emitter transducer means directs an ultrasound beam at an angle less than the first critical angle for a material body.
This produces primary longitudinal and transverse ultrasound beams within the material body.
The primary longitudinal beam is directed within the material body to the volume to be inspected.
The transverse beam is directed within the material body to a second surface so as to generate upon reflection a secondary longitudinal beam directed to the inspection volume.
Preferably, the angle of incidence of the transverse beam on the second surface is between 25.
degree.
and 35.
degree.
.
The inspection volume is thus illuminated from two different directions by longitudinal ultrasound beams.
A receiver transducer means is positioned to detect reflections from the primary and secondary longitudinal beams from a potential defect within the inspection volume.
Once the emitter transducer is activated, the receiver transducer can detect the reflection of the primary longitudinal beam and then the reflection of the secondary longitudinal beam.
In addition to allowing inspection of more volume of the nozzle than conventional techniques, the reflection of a second beam can provide confirmation of a detected flaw, increasing reliability.
In practice, emitter and receiver transducers can be mounted a fixed distance apart and at fixed relative orientations.
The transducers can then be moved in unison along a predetermined path, closed or open.
A series of ultrasound pulses can be emitted at successive positions, and the resulting reflections can be monitored and recorded.
The data so obtained can be analyzed collectively to obtain defect signatures allowing precise characterization of defects.
The present invention is contrasted with the prevailing ultrasound technique of directed ultrasound energy at an angle between the first and second critical angles for the material body.
This approach rejects the longitudinal mode, admitting only the transverse mode into the body