Vol 55, No 7 (2019)

For the previously proposed model of the corner reflector with a convex cylindrical surface at the base, intended for simulating crack-like corrosion–mechanical defects, formulas for high-resolution acoustic in-line inspection tool (ILI) have been derived in the geometrical acoustics approximation. Based on simulation results, it is demonstrated that the geometrical characteristics of the proposed model of the corner reflector affect the amplitude of angled incident transverse waves reflected from its surface in comparison with the model of a corner reflector coming to a flat surface prescribed by technical regulations.

Methods have been developed in ultrasonic flaw detection for recording and analyzing echo signals with the aim to determine the type of a reflector and its dimensions. The TOFD method allows one to distinguish between a crack and a volume reflector based on the phase of echo signals and highly accurately determine the crack height. However, it can be difficult to isolate a useful signal if it is against a noisy background. In addition, in the TOFD, it is impossible to determine reflector’s offset from the center of a welded joint without scanning across the weld. The method of digital focusing with an antenna (DFA) allows producing high-quality images over the entire volume of the welded joint, but only the amplitude of the DFA image is commonly analyzed without taking its phase into account. In this paper, we utilize the strengths of these two methods in analyzing the image of reflectors; this makes it possible to more accurately determine reflector type and coordinates in the presence of noise. Numerical and model experiments have confirmed the efficiency of the approach proposed.

Dependences of the polarization characteristics of light reflected by various surfaces have been studied. A heterogeneous system was analyzed by the method of partitioning and physicomathematical modeling of the structure, with “effective substrate” or “effective layer” model used. A method for measuring the polarization of reflected radiation has been developed and its polarization characteristics have been studied experimentally. It is shown that for all samples, the azimuth of polarization of reflected light decreases with increasing the angle of radiation incidence. It has been established experimentally that light reflected from the samples under study remains virtually linearly polarized.

The evolution of temperature fields and the deformation behavior of samples of VT1-0 titanium and zirconium Zr–1 wt % Nb alloys in coarse-grained and ultrafine-grained states is investigated under quasistatic stretching using infrared thermography. It is shown that the nature of the evolution of the temperature field in the process of deformation and the dependence of the maximum temperature on the strain in the working area differ for VT1-0 titanium and Zr–1 wt % Nb and depend on their structural and phase states, mechanical characteristics, and thermal diffusivity. It has been established that upon transition to the ultrafine-grained state, thermal diffusivity decreases by 6.5 and 9.3% for VT1-0 titanium and Zr–1 wt % Nb alloy, respectively. Differences in the deformation behavior of samples of VT1-0 titanium and Zr–1 wt % Nb alloy in the coarse-grained and ultrafine-grained states are associated with substructural hardening of the matrix phases of α-Ti and α-Zr and solid-solution hardening caused by the dissolution of β-Nb particles as the alloys under study are transferred into the ultrafine-grained state by severe plastic deformation.

In many medicine and industry applications, a precise X-ray tomography reconstruction of the internal objects structure is of great importance for reliable interpretation data. The tomography allows obtaining a spatial distribution of the internal materials structure. In certain experiments conditions, the projection data acquisition is guided by angle limitations or a restricted angle, this requires a subsampling of the projections number or a partial data absence. Accordingly, the reconstructed images may suffer from severe artefacts especially with the presence of noise. In this context, the purpose of this paper is to propose a tomographic image reconstruction method based on FBP associated to sinogram inpainting. The studied inpainting technique is based on first order variational methods such as the Chambolle-Pock algorithm. This method allows the quality improvement of the reconstruction images tomographic with reduced number of projection. The PSNR is improved by 7 to 10 dB in the reconstructed image compared to the classical FBP reconstruction.