Definition and commonly used test blocks for rail flaw detection

Definition of block - The sample used to identify the characteristics of the ultrasonic testing system and the sensitivity of flaw detection is called a test block.

Test blocks can be divided into standard test blocks, comparative test blocks and special test blocks according to the verification department and the use environment.

1. The purpose of the test block

1. Determine the appropriate flaw detection method.

2. Determine the sensitivity of flaw detection and evaluate the size of defects.

3. Calibrate the instrument and test the performance of the probe and the instrument.

2. Classification of test blocks

Test blocks can be divided into three categories: standard test blocks, comparison test blocks and special test blocks according to the verification department and the use environment.

1. Standard test block

Standard test block—refers to the test block whose material, shape, size and performance have been verified by the competent authority or authoritative organization, and is used for performance testing and sensitivity adjustment of ultrasonic testing devices or systems.

This test block is a test block specified by the national TB1152-81. It has the following three differences compared with the international standard test block IIW. wave, to correct the shear wave scanning speed; the second is to change the 50 holes to 40, 44, and 50 step holes, which is conducive to the determination of the resolution of the oblique probe; the third is to change the refraction angle to K value. Its uses are as follows:

(1) Using a thickness of 25 mm and a height of 100 mm, measure the horizontal, vertical linearity, dynamic range of the flaw detector, adjust the longitudinal wave detection range, and correct the baseline.

⑵ Use R50 and R100 to adjust the shear wave detection range, zero correction and determine the incident point (frontal length) of the oblique probe.

(3) Measure the resolution of straight probes with heights of 85, 91, and 100 mm; measure the resolution of oblique probes with curved surfaces of 40, 44, and 50 mm.

⑷Use the 50 curved surface and 1.5 horizontal hole to measure the K value of the oblique probe.

⑸ Use 50 plexiglass blocks to measure the blind area and penetration of the straight probe.

⑹ Use the right-angled edge of the test block to measure the deflection angle of the acoustic axis of the oblique probe.

 

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