There are various classifications of ultrasound transducers, and each type of transducer also has its specific application scenarios. The following are some of the main classifications and applications:

Classification

1. According to the waveform generated in the tested work piece

Longitudinal wave transducer: commonly referred to as a straight probe, mainly used to detect defects parallel to the detection surface, such as plates, castings, forgings, etc.

Transverse wave transducer: a transducer with an incident angle between the first critical angle and the second critical angle and a refracted wave of pure transverse waves, mainly used to detect defects perpendicular or at a certain angle to the detection surface, widely used for the detection of welds, pipes, and forgings.

Plate wave (Lamb wave) transducer: used to detect defects in thin plates.

Crawling wave transducer: Due to the angle of one crawling wave being between 75 ° and 83 °, almost perpendicular to the thickness direction of the inspected work piece, it is close to 90 ° with cracks in the vertical direction of the work piece. Therefore, it has good detection sensitivity for vertical cracks and does not require high roughness on the surface of the work piece, making it suitable for surface and near surface crack detection.

Surface wave transducer: The incident angle should be near the critical angle at which Rayleigh waves are generated, usually slightly larger than the second critical angle. The energy is concentrated within two wavelengths below the surface, and the sensitivity to detecting surface cracks is extremely high. It is mainly used to inspect surface or near surface defects.

2. Follow the direction of the incident sound beam

Direct transducer: used for transmitting and receiving longitudinal waves.

• Angle probe: used for transmitting and receiving transverse waves.

3. Number of piezoelectric chips in the transducer

Single crystal transducer: only one piezoelectric chip.

Double crystal transducer: There are two piezoelectric chips, one for emitting ultrasonic waves and the other for receiving ultrasonic waves. It has high sensitivity, less clutter, small blind spots, small near-field area length in the work piece, and adjustable detection range. It is mainly used to detect near surface defects.

Poly crystalline transducer: contains multiple piezoelectric chips.

4. Other classification methods

According to the coupling method between the transducer and the surface of the work piece being tested, it can be divided into contact transducers and immersion transducers.

According to whether the ultrasonic beam is focused or not, it is divided into focused probes and non focused probes.

According to the ultrasonic spectrum, it can be divided into wide band and narrowband transducers.

According to the matching detection of the curvature of the work piece, it can be divided into flat transducers and curved transducers.

There are also special transducers used to meet the detection needs under special conditions.

Application

When selecting an ultrasonic transducer, it is necessary to comprehensively consider factors such as the shape and material of the work piece, possible defect locations and directions, detection purposes and conditions. For example:

When detecting work pieces with a large area range, it is advisable to use large crystal transducers to improve the detection efficiency; When detecting thick work pieces, it is also advisable to use large crystal transducers in order to effectively detect defects at long distances.

For small work pieces, in order to improve the positioning and quantitative accuracy of defects, it is advisable to use small crystal transducers; For work pieces with uneven surfaces and large curvatures, it is advisable to use small crystal transducers to reduce coupling losses.

In transverse wave detection, the K value of the probe (the tangent of the refractive angle) has a significant impact on the detection sensitivity, the direction of the beam axis, and the acoustic path of the primary wave (the distance from the incident point to the bottom reflection point). Therefore, it is necessary to select an appropriate K value based on the thickness of the work piece in order to optimize the detection effect.

In short, the selection of ultrasonic probes should be determined based on specific testing requirements and work piece characteristics.