Variable Zoom technique for X-Ray Computed Tomography

Abstract

X-ray Computed Tomography has proven its unprecedented objectivity for nondestructive inspection of materials and structures. However, high-resolution nondestructive evaluation of small critical flaws in structures with large in-plane dimensions has been a fundamental challenge for the CT techniques. This work presents a novel Variable Zoom X-ray CT technique that can significantly improve defect resolution for structures with large in-plane dimensions. The details of the scanning technique and the reconstruction method essential for achieving accurate high-resolution results are provided. Superior performance and accuracy of the technique is demonstrated on the dimensional and sharpness measurements of known features in the artificial phantom and in X-ray CT of composite panel with large in-plane dimensions. Application of the new approach is demonstrated on the detection of complex structural damage due to low-velocity impact in large and thin composite laminate panels, which is among the worst-case scenario for the conventional CT methods.