Radiographic inspection

Radiology (Radiology) has a very wide range of applications in industry. At present, radiographic testing can be divided into four categories according to the definition of the American Society for Testing and Materials (ASTM): photographic testing, real-time imaging testing, tomographic testing and other radiographic testing technologies.

There is no essential difference between X-rays and natural light. They are both electromagnetic waves, but the energy of X-rays is much greater than visible light. It can penetrate objects that cannot be penetrated by visible light, and while penetrating objects, it will have complex physical and chemical interactions with substances, which can ionize atoms, cause certain substances to emit fluorescence, and can also cause certain substances to produce photochemistry. reaction. If there is a defect in a local area of the workpiece, it will change the attenuation of the object to the rays and cause the intensity of the transmitted rays to change. In this way, using a certain detection method, such as the use of film sensitization, to detect the intensity of the transmitted rays, you can judge whether there are defects in the workpiece. And the location and size of the defect.

ΔI/I=-(（μ-μ’）ΔT)/(1+n)

This formula is the relational expression of the basic principle of ray detection. ΔI/I is called object contrast, (I is the ray intensity, μ is the linear attenuation coefficient, ΔT is the thickness difference in the ray irradiation direction, and n is the scattering ratio). From it we can It is known that as long as the defect has a certain size in the transmission direction, its attenuation coefficient has a certain difference from the object's linear attenuation coefficient, and the scattering ratio is controlled within a certain range, we can obtain the contrast difference due to the existence of the defect, and find defect.