As one of the five conventional nondestructive testing methods, X-ray detection has been widely used in industry.

δI/I =-((μ-μ’)δT)/( 1+n)

This formula is the relational expression of the basic principle of X-ray inspection, δ I/I is called the contrast of the object, (I is the ray intensity, δ I is the increment of the ray intensity, μ is the linear attenuation coefficient of the material, μ' is the linear attenuation coefficient of the defect, δ T is the thickness difference in the radiation direction, and n is the scattering ratio). From this, we can know that as long as the defect has a certain size in the transmission direction, its attenuation coefficient is different from that of the object, and the scattering ratio.