The function of ultrasonic probe

The ultrasonic probe is just like its eyes for ultrasonic testing. The probe has a great influence on the test results. As the saying goes, if a worker wants to be good at his work, he must first make use of his tools. In the actual test process, he should carefully select according to the workpiece conditions, test conditions, defects and the implementation standards, so as to make the ultrasonic test as accurate, reliable and efficient as possible. In addition, for the performance index of the probe and the related requirements of the combined performance index of the probe and the instrument, please refer to JB / t10062 probe, JB / t9214 A-type ultra detection system performance, GB / t18694 probe and sound field, en12668-2 probe, en12668-3 combined performance, iso10375 probe and sound field, ASTM e1065 probe and other relevant standards.

1) Longitudinal wave probe is usually called straight probe, which is mainly used to detect defects parallel to the detection surface, such as plate, casting, forging detection, etc.

2) The shear wave angle probe is a probe which uses the shear wave to detect. It is a probe whose incidence angle is between the first critical angle and the second critical angle and whose refraction wave is pure shear wave. It is mainly used to detect defects perpendicular to or at a certain angle to the detection surface. It is widely used in the detection of welds, pipes and forgings.

3) The longitudinal wave angle probe is a probe whose incident angle is less than the first critical angle. The purpose is to use the small angle P-wave for defect inspection, or in the case of excessive attenuation of S-wave, to use the characteristics of strong penetration of P-wave for oblique incidence inspection of P-wave. Attention should be paid to the interference of S-wave in the test piece at the same time.

4) Creeping wave probe. Because the angle of primary creeping wave is between 75 ° and 83 °, almost perpendicular to the thickness direction of the inspected workpiece, and nearly 90 ° to the crack in the vertical direction of the workpiece, it has better detection sensitivity for the vertical crack, and the requirement for the surface roughness of the workpiece is not high, so it is suitable for the surface and near surface crack detection.

5) The incidence angle of surface wave (Rayleigh wave) probe should be near the critical angle of generating Rayleigh wave, which is usually slightly larger than the second critical angle. Because the energy of surface wave is concentrated in two wavelengths below the surface, the sensitivity of surface crack detection is very high, and the surface or near surface defects are mainly inspected.

6) Double crystal probe. The bicrystal probe has two piezoelectric chips, one is used to transmit ultrasonic wave, the other is used to receive ultrasonic wave. According to the different incident angle α L, it is divided into longitudinal wave bicrystal straight probe and transverse wave bicrystal oblique probe. The bicrystal probe has the following advantages: high sensitivity, small blind area with less clutter, small length of near-field area in workpiece, adjustable detection range. The bicrystal probe is mainly used to detect near surface defects.