A procedure for measuring the geometry of X-ray computed tomography (CT) instruments is applied to an experimental CT instrument. In this study, the geometrical measurement procedure is implemented with the CT 2 reference object, comprising steel spheres with known center positions in a local coordinate frame affixed to a cylindrical carbon fiber framework. The procedure can be implemented with other sphere-based reference objects, provided the sphere center coordinates are known. The effects of number of acquired projections and rotation mode (stepped or continuous) on the quality of measured geometrical parameters are studied. Finally, the output of the geometrical measurement procedure is used to inform the physical adjustment of the experimental CT instrument to its ideal alignment. The effectiveness of the measurement procedure to correctly determine the instrument geometry is demonstrated from dimensional measurements performed on a tomographically reconstructed validation object from radiographs acquired under initial (misaligned) and adjusted (aligned) instrument geometry.
We present a novel dual-source/dual energy (DSCT/DECT) micro-tomography system including results of high-resolution DSCT reconstruction. The DSCT micro-tomography setup was designed as a multi-purpose X-ray imaging device equipped with two pairs of X-ray tubes and detectors in orthogonal arrangement with independent control of beam parameters. Both pairs (tube-detector) are mounted on a computer numerical control positioning system and can be independently set up to different geometries (e.g. with different magnification of each pair). In this work the simultaneous scanning of the object by two tube-detector pairs was used for approximately half reduction of tomography scanning time. The developed imaging procedure was applied for scanning of a wooden sample locally damaged during a semi-destructive test for assessment of wood quality. Prior to the tomography measurements the setup geometry was precisely adjusted in terms of magnification, horizontal and vertical tube-specimen-detector alignment of both pairs. DSCT measurements were carried out in sequence (2 × 90 • for each tube) with identical 100 µm image resolution. It was proven that the presented experimental setup combined with appropriate control technique significantly reduces tomography scanning time of materials with complex micro-structure.
In this work, an in-house designed table top loading device equipped with a bioreactor is used for the in-situ compression of a spongious sample in simulated physiological conditions. On-the-fly 4D computed tomography is used as a tool for the advanced volumetric analysis of the deforming microstructure of the specimen. The loading device with the bioreactor was placed directly onto the rotational stage of a modular X-ray scanner. As the loading device is equipped with a slip-ring cable system, it can perform an unlimited number of revolutions during the on-the-fly scanning procedure. A complementary metal-oxide-semiconductor flat panel detector with a fast readout was used for the acquisition of the X-ray images. The specimen was compressed with a low loading velocity. A set of the volumetric data capturing the deformation of the specimen during the experiment was prepared from the images acquired by the detector. A digital volume correlation algorithm was used for the evaluation of the volumetric strain fields in the specimen.
K: Computerized Tomography (CT) and Computed Radiography (CR); Detection of defects; Inspection with x-rays 1Corresponding author.
Advanced pore morphology (APM) foam elements are almost spherical foam elements with a solid outer shell and a porous internal structure mainly used in applications with compressive loading. To determine how the deformation of the internal structure and its changes during compression are related to its mechanical response, in-situ time-resolved X-ray computed microtomography experiments were performed, where the APM foam elements were 3D scanned during a loading procedure. Simultaneously applying mechanical loading and radiographical imaging enabled new insights into the deformation behaviour of the APM foam samples when the mechanical response was correlated with the internal deformation of the samples. It was found that the highest stiffness of the APM elements is reached before the appearance of the first shear band. After this point, the stiffness of the APM element reduces up to the point of the first self-contact between the internal pore walls, increasing the sample stiffness towards the densification region.
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