Radiographic flaw detection is a method that uses the penetrability and linearity of rays to detect flaws. Although these rays cannot be directly detected by the naked eye like visible light, they can sensitize photographic films and can also be received by special receivers.
Rays commonly used for flaw detection include x-rays and gamma rays emitted by isotopes, which are called x-ray flaw detection and gamma ray flaw detection respectively. When these rays pass through (irradiate) a material, the greater the density of the material, the more the intensity of the rays is attenuated, that is, the less intense the rays can penetrate through the material. At this time, if a photographic film is used to receive the signal, the light sensitivity of the film will be small; if an instrument is used to receive the signal, the signal obtained will be weak.
Therefore, when irradiating the parts to be inspected with rays, if there are defects such as pores and slag inclusions inside, the density of the material passed by the rays passing through the defective path is much smaller than that of the path without defects, and its intensity will be The less it is weakened, that is, the transmitted intensity is greater. If a film is used to receive it, the light sensitivity will be greater, and the plane projection of the defect perpendicular to the direction of the ray can be reflected on the film; the same can be done if other receivers are used. Instruments are used to reflect the plane projection of the defect perpendicular to the ray direction and the amount of ray transmission.
It can be seen that under normal circumstances, it is not easy to find cracks by radiographic inspection, or in other words, radiographic inspection is not sensitive to cracks.
