PT, RT, MT, RT. How to take the certificate? Which one is more useful and valuable? How are each graded? Will it be easy to find a job after passing the exam?

Non-destructive testing methods include the above, but it is not to say which one is more useful. Professionally speaking, it should be that various testing methods must learn from each other’s strengths and weaknesses to achieve the test result requirements. Compared with what you have heard, UT.RT is more useful, and each method is divided into beginner and intermediate levels.

Ultrasound is a mechanical wave with a frequency higher than 20 kilohertz. The commonly used frequency in ultrasonic flaw detection is 0.5-5 MHz. This kind of mechanical wave can propagate at a certain speed and direction in the material, and will be reflected when it encounters heterogeneous interfaces with different acoustic impedances (such as defects or the bottom surface of the object being measured, etc.).

This reflection phenomenon can be used for ultrasonic flaw detection. The most commonly used method is pulse echo flaw detection. During flaw detection, the voltage emitted by the pulse oscillator is applied to the probe (made of piezoelectric ceramics or quartz wafers). (formed detection element), the ultrasonic pulse emitted by the probe enters the material through the acoustic coupling medium (such as engine oil or water, etc.) and propagates in it. After encountering a defect, part of the reflected energy returns to the probe along the original path, and the probe converts it into electricity. The pulse is amplified by the instrument and displayed on the fluorescent screen of the oscilloscope tube.

According to the position and amplitude of the defect reflection wave on the fluorescent screen (compared with the reflection wave amplitude of the artificial defect in the reference test block), the position and approximate size of the defect can be determined. In addition to the echo method, there is also the penetration method that uses another probe to receive signals on the other side of the workpiece. When using ultrasonic method to detect the physical properties of materials, the sound speed, attenuation and vibration characteristics of ultrasonic waves in the workpiece are often used.