A New Ultrasonic Transducer Combining Three Modes: High Axial Resolution, High Transverse Resolution and Standard Modes
Ultrasonic methods of nondestructive testing become more and more quantitative. They aim not only to detect but also to identify and characterize defects. This results in contradictory requirements for transducer design. One sought improvements in axial resolution for a given frequency range in reducing the pulse duration, leading to low sensitivity and failing in the case of small defects close to the transducer. Good transverse resolution with a planar transducer is obtained by using it in its pseudo-focal zone in which the ultrasonic beam is narrow, that is, at a range corresponding to the limit of the near-field, even if this range is ill-defined in the case of a broad band transducer.
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