Calibration method of ultrasonic straight probe, double crystal probe and angle probe
In ultrasonic testing, the calibration of sound speed and probe zero point is because the calculation of parameters displayed in the status line is related to sound speed and probe zero point, so it is necessary to calibrate before flaw detection; the calibration of sound path is to display the waveform within the appropriate range of sound path on the screen, so as to better judge and evaluate defects.
1、 Straight probe calibration (single crystal probe)
Determine the calibration procedure according to the known sound speed and probe zero point. If the speed of sound is unknown, the speed of sound shall be calibrated first; if the speed of sound is known, skip the speed of sound calibration, adjust the speed of sound to known speed, and then use one point method to calibrate the probe zero point.
1. Sound velocity calibration of known materials
Step:
(1) The material sound speed is set to a known material sound speed,
(2) Coupling the probe to the calibration block,
(3) Set the gate logic as a single gate mode, that is, set it as the incoming wave alarm or the loss of wave alarm logic, and trap the gate with the primary echo. At this time, the sound path measurement is the sound path at the primary echo,
(4) Adjust the probe zero point so that the sound path measurement value (s) in the state line is the same as the known thickness of the test block, and the probe zero point obtained at this time is the accurate probe zero point of the probe.
2. Sound velocity calibration of unknown material
Step:
(1) First, set a preliminary sound velocity value;
(2) The logic of regulating gate is double gate mode;
(3) Coupling the probe to a test block with the same material and known thickness;
(4) Move the starting point of gate a to the primary echo and intersect with it. Adjust the height of gate a to be lower than the maximum amplitude of the primary echo to a proper position. Gate a cannot intersect with the secondary echo;
(5) Move the starting point of gate B to the secondary echo and intersect with it, adjust the height of gate B to be lower than the maximum amplitude of the secondary echo to a proper position, and gate B cannot intersect with the primary echo;
(6) Adjust the sound speed so that the sound path measurement value (s) displayed in the status line is the same as the actual thickness of the test block. At this time, the sound speed obtained is the accurate sound speed value under this flaw detection condition.
(7) Set the gate logic as a single gate mode, that is, set it as the incoming wave alarm or the loss of wave alarm logic, at this time, the sound path measurement is the sound path at the primary echo;
(8) Adjust the probe zero point so that the sound path measurement value (s) in the state line is the same as the known thickness of the test block, and the probe zero point obtained at this time is the accurate probe zero point of the probe.
The sound velocity of the material is unknown, the sound velocity of the approaching material is set to 5920 M / s, the logic of the gate is set to double gate mode, and the zero point of the probe is set to 0; the probe is coupled to a 50 mm calibration block, and the gate a is adjusted to the position intersecting with the primary echo, and the gate B is adjusted to the position intersecting with the secondary echo;
2、 The sound velocity value is increased by the calibration of double crystal probe until the displayed value of sound path between the primary and secondary echoes is 50mm, and now the accurate sound velocity of the material is measured to be 6024m / S; then the gate is set as a single gate mode to measure the sound path at the primary echo, and the probe zero point is adjusted continuously until the measured value of sound path at the primary echo is 50mm, and now the probe zero point is 0.125us.
Calibration procedure:
(1) Set the dual probe status in the transceiver group;
(2) According to the current test task and the selected probe, set the sound path and the function items of the transceiver group;
(3) Coupling the probe to the calibration block, adjusting the probe zero point in the basic group until the calibration echo is close to the required position, and the secondary echo is also within the display range;
(4) Adjust the gain value until the echo with the maximum amplitude is close to the full screen height;
(5) Open the double gates in the gate group;
(6) Select the leading edge measurement mode in the setting function group;
(7) Moving the starting point of gate a to the primary echo and intersecting with it, gate a cannot intersect with the secondary echo;
(8) Move the starting point of gate B to the secondary echo and intersect with it. Gate B cannot intersect with the primary echo;
(9) Adjust the gate height so that it is at the same position as the front of the two calibration echoes;
(10) Then change the sound speed until the thickness of the calibration block is displayed;
(11) Set the gate logic as a single gate mode, that is, set it as the incoming wave alarm or the loss of wave alarm logic, at this time, the sound path measurement is the sound path at the primary echo;
(12) Adjust the probe zero point so that the sound path measurement value of the state line is the same as the known thickness of the test block.
3、 Angle probe calibration
1. Calibrate the incident point (probe front): measure the zero point of the angle probe with IIW test block (also known as Dutch test block) or CSK-IA test block. First, adjust the sound speed of the instrument to 3230m / s, and the display range is 150 mm. Then start the test. The user places the probe on the test block as shown in the figure and moves it, so that the echo of the reflector on the circular surface of r100mm reaches the highest. Measure the front end face of the probe and r100mm of the test block with a ruler Arc center distance, which is the leading edge value of the probe, and the position of r100mm arc center corresponding to the probe is the incident point of the probe. The following steps are usually required for calibration of angle probe: 1. Calibrate the incident point (probe front); 2. Calibrate the probe angle (k value); 3. Calibrate the material sound speed; 4. Calibrate the probe zero point.
2. Calibration probe angle (k value): the probe calibrated with angle value can be calibrated with IIW test block, and if it is calibrated with K value, it can be calibrated with CSK-IA test block. For the scale with angle or K value on the two test blocks, select the appropriate scale according to the nominal value of the probe (as shown in the right figure, 60-76 degree probe can be calibrated on the upper side of IIW test block, 74-80 degree probe can be calibrated on the lower side, k2.0, k2.5 and k3.0 probes can be calibrated on the upper side of CSK-IA test block, k1.0 and K1.5 probes can be calibrated on the lower side. Please select the appropriate calibration block and calibration method according to the calibration value on the test block). Place the probe as shown in the figure, move left and right to make the echo of the reflector reach the maximum. At this time, the scale corresponding to the incident point is the angle or K value of the probe.
3. Calibrate the sound velocity of the material to find the highest reflection wave of r100mm as described in 1, adjust the display range to enable the secondary echo of the arc surface to be displayed on the screen, select the gate mode as double gate, adjust the intersection of gate a and primary echo, adjust the intersection of gate B and secondary echo, adjust the sound velocity value to make the measured value (s) of the sound path in the status line 100, and the sound velocity value obtained at this time is the material The actual sound velocity of the material.
4. Calibrate the probe zero point to maintain the above measurement state, change the gate mode to positive or negative, adjust the probe zero point to make the sound path measurement value (s) in the state line to 100 again, at this time, the obtained probe zero value is the probe zero value.
There are many calibration methods for angle probe, which are not entirely constrained by the calibration with standard test blocks, but also can be calibrated with holes of known depth. Theoretically, the smaller the reference reflector is, the higher the accuracy of calibration is, but the difficulty of calibration is also correspondingly increased. The angle can be calibrated by measuring the depth and horizontal position of the small hole, calculating the slope, and the sound speed and probe zero point can be calibrated by using the measured depth or horizontal position value.