Ultrasonic thickness gauge detection

The detection and localization of defects using ultrasonic thickness gauges are based on the measurement of ultrasonic echo signals.

The constant speed of sound in the detection object is an important factor affecting the accuracy of the detection results. Therefore, to achieve high detection accuracy, it is necessary to have a relatively constant ultrasound propagation speed in the detection object. The following 5 points should be noted.

The sound velocity of ultrasonic thickness gauge materials will change with the temperature of the material.

If the calibration of the instrument is carried out in an environment with relatively low temperatures, but the use of the instrument is in an environment with relatively high temperatures, this will cause the detection results to deviate from the true values.

To avoid the influence of temperature, the method is to use a high-temperature probe to calibrate the instrument.

2. The influence of surface roughness on ultrasonic thickness gauge

The surface roughness of the tested piece has an impact on the thickness gauge. The roughness increases and the impact increases.

Rough surfaces can cause systematic and accidental errors. During each measurement, the number of measurements should be increased at different positions to overcome these accidental errors.

3. The influence of attached substances on ultrasonic thickness gauges

Before thickness measurement, it is necessary to clean the attached substances to ensure direct contact between the instrument probe and the surface of the tested part.

4. Magnetic field of ultrasonic thickness gauge

The strong magnetic field generated by various electrical equipment around can seriously interfere with thickness measurement work.

5. The influence of ultrasonic thickness gauge materials

In the detection object of steel, even if it contains multiple different alloy components, its sound speed is considered to be basically constant.

In many other materials, such as many non-ferrous metals or plastics, the variation of ultrasonic propagation speed is very significant, which can affect the accuracy of measurement.

If the material of the object to be tested is not isotropic, the speed of sound will vary in different directions.

In this case, the average value of the sound speed within the detection range must be used for calculation. The average value is obtained by measuring a reference block whose sound speed is equivalent to the average sound speed of the test block.