In this work, two innovations were demonstrated for in-situ 3D study of fatigue cracks and their closure as a function of applied load. The first related to improvements in how absorption microtomography is used to study fatigue cracks. The second is a new approach to 3D crack mapping relying on X-ray phase imaging and stereometric approaches. Absorption microtomography was used to determine crack surface positions. Crack opening was measured from absorption microtomography data both before and after crack extension and patterns of opening at several loads were analyzed for both cases. X-ray phase contrast imaging, an alternative approach to absorption microtomography, whose sensitivity to cracks is not strongly affected by the shape of the specimen, was also investigated. Increased sensitivity of phase imaging to cracks, compared to that of the absorption X-ray methods, allowed detecting crack positions up to the crack tip with no load applied to the sample. Stereometry reconstruction based on the phase microradiographs was carried out, and the results were compared with those of absorption microtomography on the same specimen. This study demonstrated that it is possible to reconstruct accurate 3D positions of features inside optically opaque sample by recording several X-ray phase microradiographs.

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X-ray computed tomography is a nondestructive method for 3D imaging of inner structure of objects; it is, however, restricted by absorption properties of materials. With phase contrast imaging, observation of samples with low absorption or with parts with similar absorption becomes possible. For a long time, phase contrast imaging has been restricted to synchrotron radiation sources or special techniques due to requirement of spatial coherence of radiation. Along with recent development of X-ray micro and nanofocus tubes and X-ray detectors a phase contrast imaging becomes available also with laboratory sources. In this work an overview of phase contrast imaging methods is given, with an emphassis on propagation based method. Examples of this method and application of phase retrieval algorithm on samples from RIGAKU Nano3DX and GE phoenix v|tome|x L240 stations within Laboratory of X-ray micro and nanotomography CEITEC BUT are shown.

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No description available.

As an intrinsic requirement for digital image correlation (DIC)to be applicable, the images must exhibit a speckle pattern of sufficient unique features. Researchers have incorporated X-ray phase contrast imaging (PCI) and DIC (XDIC) and conducted studies on materials with natural internal features as speckles. This study is the first attempt to explore the applicability and standards of XDIC to be applied on materials that are transparent under X-ray PCI, mainly polymers, by deliberately embedding particles into the sample. The goal is to generate a high-quality speckle while maintaining the least influence on the material’s properties. Iron oxide (FeO), tungsten carbide (WC), and platinum (Pt) are embedded into Sylgard® epoxy at various weight ratios, and the Sylgard® samples are loaded with a Kolsky compression bar paired with high-speed X-ray PCI. The speckle quality of the PCI images is assessed using a mean intensity gradient based approach, as well as intensity distribution analysis. DIC is applied to the images to measure the displacement field in the loading direction, and the results are analyzed. The engineering stress-strain relationship is generated from the Kolsky bar apparatus, and the results are compared to find the influence of the added particles.<div><br></div><div>The results indicate thatthe addition of particles does not significantly alter the base polymer’s properties, and the theoretical deviation error can be as low as less than 0.01 pixels. Disregarding the limited applicability to embed into polymer samples, platinum produces the best speckle. WC particle is the superior choice of material to embed for its good speckle quality, ease of embedding, and good availability. Lower weight ratios are shown to be preferential. This study also emphasizes the importance of sample design when applying XDIC to materials with embedded particles. It is preferential for best accuracy to design the region of interest to be away from the surfaces of the samples and be located near the back of the sample with respect to the impact surface.<br></div>

La tomographie par rayons X est une technique d’imagerie non-invasive qui permet de réaliser des images en 3D par l’acquisition de multiples images en 2D. La tomographie X par contraste de phase (XPCT) a été utilisée pour étudier la biodistribution de nanoparticules métalliques (NPs) dans des souris. Ces NPs sont très utilisées comme radiosensibilisants dans la recherche de traitements contre les cancers mais aussi pour marquer des plaques amyloïdes de la maladie d’Alzheimer chez la souris. Grace à la grande brillance du synchrotron ESRF, des images XPCT en haute résolution ont été obtenues et traitées pour produire des modèles en 3D d’organes de souris dopés aux NPs de gadolinium, d’or ou de platine.En parallèle, dans le cadre du projet Européen VOXEL (Volumetric X-ray Extremely Low dose), un microscope compact à rayons X mous a été développé pour l’imagerie cellulaire. Ce microscope fonctionne dans la « fenêtre de l’eau », une région spectrale pour laquelle un bon contraste de la structure cellulaire est réalisable naturellement. Ce microscope est conçu pour réaliser de l’imagerie plénoptique, une technique actuellement testée uniquement dans le visible. Ce système est composé d’une lentille principale et d’une matrice de micro-lentilles couplée à un détecteur, permettant d’enregistrer les composantes angulaires et spatiales des rayons arrivant au niveau du détecteur. Il est ainsi possible de produire des images en 3D à partir d’une seule exposition. Adapter cette technique disruptive aux rayons X aura, un très grand impact pour les applications biomédicales car cela permettra de réduire fortement la dose absorbée par les échantillons par rapport à la méthode conventionnelle de tomographie X. / X-ray tomography is a non-invasive imaging technique that allows producing 3D images following the acquisition of multiple 2D images at many angles. In particular, X-ray Phase-Contrast Tomography (XPCT) has been exploited for resolving the biodistribution of metal-based theranostic nanoparticles (NPs) in mice. These NPs are widely used as radiosensitizers for researches on cancer therapies and, recently to mark amyloid plaques in Alzheimer’s disease in mice. Thanks to the high brightness of ESRF synchrotron, high resolution XPCT images were obtained and thus processed for producing 3D models of mice organs doped with gadolinium, gold or platinum NPs.In parallel, in the framework of a European project, named VOXEL (Volumetric X-ray Extremely Low dose), a compact desktop-size soft X-ray microscope was developed aiming at biological cell imaging. The microscope was designed to be suitable in the so-called “water window” spectral range, where a natural good contrast of the cellular structures is achievable. The microscope was conceived to perform plenoptic imaging, a technology currently tested only in the visible domain. This device is composed of a main lens and a microlens array coupled to a detector, allowing recording the spatial and the angular components of the light rays travelling up to the detector and thus enabling producing 3D images in a single exposure. By adapting this disrupting technology to X-rays, a huge impact for bio-medical applications is foreseen, since it would lead to a drastic decrease of the dose absorbed by samples, compared to traditional X-ray tomography methods.