A Brief Analysis of the Procedure of Ultrasonic Nondestructive Testing

A Brief Analysis of the Procedure of Ultrasonic Nondestructive Testing

1. Principle of ultrasonic testing

Ultrasonic flaw detection is a non-destructive testing method, which uses the difference of acoustic properties of materials and their defects to examine the internal defects of materials.

A Brief Analysis of the Procedure of Ultrasonic Nondestructive Testing
A Brief Analysis of the Procedure of Ultrasonic Nondestructive Testing

2. Characteristics of ultrasound

  • The ultrasonic beam can be concentrated in a specific direction and propagate along a straight line in the medium, and has good directivity.
  • Ultrasonic wave attenuates and scatters when it propagates in medium.
  • Ultrasonic wave will produce reflection, refraction and wave form conversion on the interface of dissimilar medium, and the reflected wave from the defect interface can be obtained by using these characteristics.
  • Ultrasound is much more powerful than sound.
  • The transmission loss of ultrasonic wave in solid is very small and the detection depth is very large.  inspection of parts with large thickness.

2.1 Disadvantages:

  • It is difficult to display the defects directly, and it is easy to be influenced by subjective and objective factors, and the results are not easy to save.
  • The ultrasonic testing requires smooth working surface, and experienced inspectors are required to distinguish the types of defects, and it is suitable for theUltrasonic detection step

3. Ultrasonic detection step

3.1. Preparation before testing

  • Familiar with the picked workpiece (workpiece name, material, specifications, groove form, welding method, heat treatment state, workpiece surface state, inspection standard, qualification level, inspection ratio, etc.) ;
  • Select the instrument and probe (according to the standard and the field conditions, determine the detector, probe, test blocks, scanning ratio, detection sensitivity, detection mode)
  • Calibration of the instrument (the horizontal and vertical linearity of the instrument is measured when the instrument is in use.)
  • Probe calibration (for front edge, refraction angle, main beam deviation, sensitivity margin and resolution calibration.)
  • Adjustment of the instrument (the baseline scale can be scaled to represent the horizontal distance, depth or acoustic range of the pulse echo.)
  • The adjustment of sensitivity (the sensitivity is checked on the contrast test block or other equivalent test block.)

3.2. Inspection results and ratings: according to the nature of defects, extent, indicating the length of the relevant standard rating.

3.3. Check and recheck the instruments and equipment.

3.4. Issue a test report.

4. Standard method for nondestructive ultrasonic testing of metallic materials

  • JB/T4730.3-2005 non-destructive testing of pressure equipment, ultrasonic testing
  • Manual ultrasonic testing of steel welds — methods and classification of testing results
  • CB/T 3559 -2011 marine steel weld ultrasonic detection process and quality classification

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