Ultrasonic Flaw Detector Theory

Ultrasonic flaw detector is one of the portable non-destructive industrial machines, which can be used to detect, locate, evaluate and diagnose the internal flaws existing in workpieces (cracks, porosity, pores, inclusions, etc.) rapidly, conveniently, and accurately with no damage. However, the principle of ultrasonic flaw detector is still hard to understand for most of our users, and here is the introduction of the ultrasonic flaw detector theory for you.

Actually, there are numerous of ultrasonic flaw detectors in the market but during the practical use, and the pulsed reflection-type ultrasonic flaw detector is most wildly used. Ultrasonic waves will be reflected at the interface of two media with different acoustic impedances. The magnitude of the reflected energy is related to the difference in acoustic impedance of the media on both sides of the interface and the orientation and size of the interface.

For the moment, most of the portable pulsed reflection-type ultrasonic flaw detector use A-scan mode. The so-called A-scan made means that the X-axis of the display is the propagation time or distance of the ultrasonic wave in the tested material, and the Y-axis is the value of amplitude of ultrasonic reflection wave. According to the ultrasonic flaw detector theory, the height and shape of the reflection wave is different due to the different defects, this difference tells the nature of the defect.

Therefore, the ultrasonic flaw detector theory is designed by the principle, that is , when the ultrasonic wave propagates in the material, it will be reflected and refracted when encountering the medium. If there are no defects in the material, the other end of the material where the ultrasonic wave propagates will reflect. After being captured by the probe, the thickness of material is judged based on the sound velocity of the wave in the material and the time between the emitted wave and the received echo during actual inspection. If there is a defect, there will also be a reflection echo, which the probe will capture.