Ultrasonic flaw detector instrument adjustment and defect location

　　1. Zero point adjustment

　　Since the ultrasonic wave enters the workpiece to be tested through the protective film, coupling agent (straight probe) or plexiglass wedge (angle probe), this part of the sound path needs to be removed when locating defects in order to obtain the actual sound path of the ultrasonic wave in the workpiece.

　　The zero point is usually adjusted by a test block with a known sound path, such as the R100 arc surface (oblique probe) or the large flat bottom with a depth of 100 mm (straight probe) in the CSK-IA test block.

　　2. K value adjustment 

　　Since the oblique probe not only needs to know the sound path of the defect, but also the vertical and horizontal positions of the defect, the oblique probe must also accurately measure its K value (refraction angle) to accurately locate the defect.

　　The K value is generally adjusted by testing a test block with a hole of known depth, such as a CSK-IA test block with a hole of ?50 or ?1.5.

　　3. Quantitative adjustment  

　　Quantitative adjustment generally uses AVG (straight probe) or DAC (angle probe).

　　4. Defect Location

　　Determining the defect position in ultrasonic flaw detection is referred to as defect location.

　　1. Longitudinal wave (straight probe) positioning

　　Longitudinal wave positioning is relatively simple. If the probe beam axis does not deviate, the position of the defect wave on the screen is the distance from the defect to the probe in the vertical direction.

　　2. Surface wave positioning

　　Surface wave flaw detection positioning is basically similar to longitudinal wave positioning, except that the defect is located on the surface of the workpiece, and the position of the defect wave on the screen is the horizontal distance from the defect to the probe (the front edge of the probe should be considered at this time).

　　3. Shear wave positioning

　　The positioning of shear wave oblique probe flaw detection is determined by the sound path of the defect and the refraction angle of the probe or the horizontal and vertical projections of the defect.

　　4. Defect location when shear wave circumferentially detects cylindrical surfaces

　　During circumferential flaw detection, defect positioning is different from that during planar flaw detection.

　　(1) Circumferential detection of external flaws

　　(2) Inner wall circumferential detection