OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 a b c d Fig. 8. Comparison of different object scanning methods. The laminography is implemented at an inclination angle of the sample q = 29.8°. In diagram а the x–y plane is marked with a red line [16] Ta b l e 1 Comparison of tomography, laminography, and augmented laminography methods [16] Computed tomography Augmented laminography Computed laminography + High resolution in the x–y plane + High resolution in the x–y plane + Equal resolution along the x, y, z axes + A significant geometric increase can be achieved + Typical CL artefacts are largely suppressed (intermediate between CL and CT z-direction resolution) − Sample must fit the field of view − Blurring in the z direction − Increased scan time − Strong attenuation for large objects Implementation of the laminography method The tilt angle of the rotary axis θ in the implementation of the SRCL method is related to the geometry of the samples and determined experimentally in each case. In order to achieve the required resolution the value of θ has to provide the optimal average value of the intensity of the transmitted radiation. The energy of X-ray radiation is calculated based on the characteristics of the material, namely, taking into account the radiation absorption index. Monochromatic X-ray radiation passing through any medium when interacting with atoms or molecules attenuates according to the Bouguer-Lambert-Beer law: 0 k l I I e λ - = , (1) where I0 is the intensity before passing through the medium with thickness l; I is the intensity at the exit from the medium. The dependence of the absorption index kλ on the wavelength of the absorbed radiation is called the absorption spectrum of the substance. In cases where the sample consists of several materials based on the absorption capacity it is necessary to select the energy level that provides optimal image contrast. In this case the absorption index is determined by the expression: ( , ) L k l f x l dl λ = ∫ , (2) where f(x, l) is the linear absorption coefficient of the material, dl is the element of the absorption path along the beam L.
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