Keywords:Ultrasonic Testing, Ultrasonic Flaw Detection
Using ultrasonic testing to detect the quality of seamless steel pipe can be done defects (corrosion, cracks, pits, etc.) is detected without damaging the pipe.
Nondestructive ultrasonic flaw detection method is the use of defective materials and acoustic performance difference on the reflections of the ultrasonic wave propagation time, energy and penetration testing material changes to internal defects. Pulse reflection method used in the vertical longitudinal wave detection, in the oblique flaw with transverse waves. Pulse wave reflection method with longitudinal and transverse flaw detection. The oscilloscope screen of the ultrasonic instrument in the abscissa represents the propagation time of the acoustic wave, the longitudinal axis indicates the amplitude of the echo signal. For the same homogeneous medium propagation time, pulse wave and sound path is proportional. Therefore, defects may occur Defective echo signals; but also by the position of the echo signal appears to determine the distance from the detection surface of the defect, the defect location realization; echo amplitude to determine by the equivalent defect size.
The advantage of ultrasonic flaw detection is large thickness, high sensitivity, high speed, low cost, harmless to human body, able to locate and quantify defects. Ultrasonic testing showed no visual defects, testing technical difficulties, vulnerable subjective and objective factors, as well as testing results are not easy to save, ultrasonic testing requirements for smooth working surface, requiring experienced inspectors can identify defect types, suitable thickness larger part inspection, ultrasonic inspection also has its limitations. Many types of ultrasonic flaw detector, ultrasonic flaw detector pulse reflection but the most widely used. Generally homogeneous material, the presence of defects will result in a discontinuous material, the discontinuity caused by the acoustic impedance often inconsistent Theorem we know by the reflection, the reflected ultrasonic wave occurs at the interface between two media of different acoustic impedances. Orientation of the energy reflected both sides of the medium size of the acoustic impedance of the interface and the interface of the difference of size. Pulse echo ultrasonic flaw detector design is based on this principle.
Pulse mostly reflected ultrasonic flaw A scanning type, i.e. the so-called A-scan display of the monitor being the abscissa is the propagation time of the ultrasonic testing of materials, or propagation distance in the ordinate is the amplitude of the reflected ultrasonic waves. For example, in the presence of a defect in the workpiece due to the presence of defects, resulting in the formation of an interface between different dielectric material between the defect and the acoustic impedance of the interface between different when the ultrasonic wave transmitted across the interface After reflection occurs, and the reflected energy received by the probe, a position on the display screen will be displayed abscissa waveform of the reflected wave, the abscissa is the position in the detected defect wave in the material depth. The height and shape of the reflected wave due to the different type of defect, reflects the nature of the defect.
Ultrasonic flaw than X-ray detection is with high detection sensitivity, short cycle, low cost, flexible, high efficiency, harmless to human body, etc.; drawback is that the requirements for a smooth working surface, requiring experienced inspectors can identify defect types, the defect did not intuitive; ultrasonic thickness testing is suitable for larger parts inspection.
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