Classification of nondestructive testing

At present, there are many methods used for nondestructive testing. In addition to the 5 conventional methods (ray, ultrasonic, magnetic particle, penetration and eddy current), there are infrared, laser, acoustic emission, microwave, industrial CT, etc.

[1] X-ray detection

Radiographic testing (radiographictesting). The difference in intensity attenuation of X-ray or gamma rays when penetrating various parts of the object is used to detect the defect of the object. If the radiation with different degrees of absorption is projected onto the X-ray film, a photograph showing the thickness changes and internal defects of the object can be obtained after development. If you use a fluorescent screen instead of film, you can directly observe the internal situation of the object being tested.

[2] Ultrasonic detection

ultrasonictesting (ultrasonictesting). The influence of the acoustic characteristics of the object itself or the defects on the ultrasonic wave propagation is used to detect the defects or some physical characteristics of the object. The ultrasonic frequency commonly used in ultrasonic testing is 0.5 to 5 MHz. The most commonly used ultrasonic test is pulse detection.

[3] Eddy current testing

eddy current testing is a non-destructive testing method based on the principle of electromagnetic induction. It is applicable to conductive materials, if we put a conductor in an alternating magnetic field, there is an induced current in the conductor, that is, eddy currents. Due to the conductor's own various factors (such as conductivity, permeability, shape, size and defects, etc.) changes will lead to changes in induced current, the use of this phenomenon to determine the nature of the conductor, the state of the detection method, called eddy current testing method.

[4] Penetration testing

penetranttesting uses the permeability of certain liquids to narrow gaps to detect surface defects. Commonly used penetrant liquids are liquids containing colored dyes or fluorescence.

[5] Magnetic particle detection

Magnetic particle testing is the detection of defects on or near the surface of an object by the accumulation of magnetic particles in the leakage field near the object defect. The object being detected must be ferromagnetic.