The Influence of Ultrasonic Flaw Detector Probes on Defect Quantification

In ultrasonic flaw detection, the performance of the probe directly affects the positioning and quantitative evaluation of defects. Ultrasonic flaw detector probe improper selection and use can lead to measurement errors, thereby affecting the accuracy of flaw detection results. This article will explore several major influencing factors to help inspectors better understand how to optimize the use of probes.

Ultrasonic Flaw Detector Probe: Sound Beam Deviation

Ultrasonic flaw detector probe the degree of deviation of the actual main sound beam from its theoretical geometric central axis is called the deviation of the main sound beam. During flaw detection, whether it is vertical incidence or oblique incidence, theoretically, the beam center and the geometric center of the probe chip should overlap. However, in actual application, the beam axis and the geometric centerline of the chip will have a certain deviation. Therefore, the deviation of the beam should be measured before flaw detection to correct the measurement results and improve positioning accuracy.

Ultrasonic Flaw Detector Probe: Double Peaks

The phenomenon where two peaks are generated by the same reflector when the probe is moved parallel is called double peaks. Generally, the sound field emitted by the probe has only one main sound beam, and the sound pressure is highest on the far-field axis. However, some probes have poor performance and have two main sound beams. When detecting defects, it is impossible to determine which main sound beam is responsible. Therefore, the actual location of the defect cannot be determined, so such probes should be carefully selected during procurement.

Ultrasonic Flaw Detector Probe: Wedge Wear

During flaw detection, the wedge of the transverse wave probe will wear out. If the operator applies uneven force, the wear degree of the front and rear of the probe wedge will be different. When the front of the wedge wears more, the refraction angle decreases, and the K value decreases. When the rear of the wedge wears more, the refraction angle increases, and the K value also increases. In addition, ultrasonic flaw detector probe wear will also cause changes in the probe's incidence point, thereby affecting defect positioning. Therefore, if probe wear is found during flaw detection, the probe parameters should be calibrated in time.

Ultrasonic Flaw Detector Probe: Directivity

Probes with a small half-diffusion angle have good directivity and small defect positioning errors; otherwise, the positioning error is large.

Ultrasonic Flaw Detector Probe: Types and Chip Sizes

Different types of defects in different locations and directions should be inspected with different types of ultrasonic flaw detector probes to reduce quantitative errors. For instance, for forgings and steel plates where defects are mostly parallel to the detection surface, longitudinal wave straight probes are suitable; for hazardous defects on weld seams that are mainly vertical to the detection surface, transverse wave probes are preferable; surface wave probes are used for surface defects; split dual-element probes are suitable for near-surface defects; multi-frequency probes can be chosen for defects with complex shapes.

The chip size will affect the near-field length and beam directivity, thus having a certain impact on quantification.

Ultrasonic flaw detector probe plays an important role in defect quantification. Factors such as beam deviation, wedge wear, probe types, and chip sizes will all affect the performance of the probe, thereby affecting the accuracy of flaw detection results. Therefore, inspectors should pay attention to the selection and use of probes and make necessary corrections and evaluations to flaw detection results to improve defect quantification accuracy. This will help ensure the quality and safety of materials and structures.