Limited projection based in-situ X-ray tomography for hard material characterization.

Mechanical loading systems are increasingly integrated with cone-beam X-ray computed tomography (CBCT) for in-situ characterization of material mechanical properties. To achieve accurate CBCT reconstruction over a 360° scanning angle, the sample chambers of mechanical loading systems are typically constructed from X-ray weakly absorbing materials. However, their limited loading capacity restricts the characterization of hard materials, and their fully enclosed design prevents sample position adjustment. Therefore, we propose a structurally flexible steel support system integrated with limited-projection in-situ CBCT to address invalid projections in partial scanning angles caused by strong X-ray attenuation of steel components, thereby significantly expanding stress loading capacity and improving operational flexibility. The improved prior image constrained compressed sensing reconstruction method incorporating total variation and non-local low-rank regularization, along with the image registration algorithm (NLR-PICCS), is proposed for in-situ mechanical non-destructive testing of hard alloy materials under high stress. The core parameters, including prior weight, registration error, and missing angle limits, are quantitatively analyzed and optimized with the missing projection angles (90°, 120°, and 180°). Compared with other major limited-projection reconstruction methods, both simulation and experimental results demonstrated the superiority of the proposed approach with the potential to provide a more extensive evaluation of material stress-strain characteristics with higher accuracy and reliability.