| 1. |
- Alhede, Andreas, 1996, et al.
(författare)
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A two-stage study of steel corrosion and internal cracking revealed by multimodal tomography
- 2023
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Ingår i: Construction and Building Materials. - 0950-0618. ; 394
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Tidskriftsartikel (refereegranskat)abstract
- Modeling of corrosion-induced cracking is limited by lacking knowledge on the behavior of corrosion products. In this work, the corrosion and cracking processes were experimentally investigated in 3D at two different stages. The processes were measured at micro-structural scale, applying nondestructive neutron and X-ray computed tomography in two scans at different stages in the corrosion process. A method to evaluate the average volumetric strain of the compressed corrosion layer was proposed and displacements in the concrete matrix were measured. Strain localization revealed cracks not directly visible in the images. Multimodal tomography demonstrated to be an effective method for investigating steel corrosion in reinforced concrete.
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| 2. |
- B. Wrammerfors, E. Tobias, et al.
(författare)
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Exploratory neutron tomography of articular cartilage
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Ingår i: Osteoarthritis and Cartilage. - 1063-4584.
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To investigate the feasibility of using neutron tomography to gain new knowledge of human articular cartilage degeneration in osteoarthritis (OA). Different sample preparation techniques were evaluated to identify maximum intra-tissue contrast. Design: Human articular cartilage samples from 14 deceased donors (18–75 years, 9 males, 5 females) and 4 patients undergoing total knee replacement due to known OA (all female, 61–75 years) were prepared using different techniques: control in saline, treated with heavy water saline, fixed and treated in heavy water saline, and fixed and dehydrated with ethanol. Neutron tomographic imaging (isotropic voxel sizes from 7.5 to 13.5 µm) was performed at two large scale facilities. The 3D images were evaluated for gradients in hydrogen attenuation as well as compared to images from absorption X-ray tomography, magnetic resonance imaging, and histology. Results: Cartilage was distinguishable from background and other tissues in neutron tomographs. Intra-tissue contrast was highest in heavy water-treated samples, which showed a clear gradient from the cartilage surface to the bone interface. Increased neutron flux or exposure time improved image quality but did not affect the ability to detect gradients. Samples from older donors showed high variation in gradient profile, especially from donors with known OA. Conclusions: Neutron tomography is a viable technique for specialized studies of cartilage, particularly for quantifying properties relating to the hydrogen density of the tissue matrix or water movement in the tissue.
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| 3. |
- Das, Arghya, et al.
(författare)
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A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables. Part II - Validation and localization analysis
- 2014
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Ingår i: Journal of the Mechanics and Physics of Solids. - : Elsevier BV. - 1873-4782 .- 0022-5096. ; 70, s. 382-405
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Tidskriftsartikel (refereegranskat)abstract
- We study the mechanical failure of cemented granular materials (e.g., sandstones) using a constitutive model based on breakage mechanics for grain crushing and damage mechanics for cement fracture. The theoretical aspects of this model are presented in Part I: Tengattini et al. (2014), A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables, Part I - Theory (Journal of the Mechanics and Physics of Solids, http://dx.doi.org/10.1016/j.jmps.2014.05.021). In this Part II we investigate the constitutive and structural responses of cemented granular materials through analyses of Boundary Value Problems (BVPs). The multiple failure mechanisms captured by the proposed model enable the behavior of cemented granular rocks to be well reproduced for a wide range of confining pressures. Furthermore, through comparison of the model predictions and experimental data, the micromechanical basis of the model provides improved understanding of failure mechanisms of cemented granular materials. In particular, we show that grain crushing is the predominant inelastic deformation mechanism under high pressures while cement failure is the relevant mechanism at low pressures. Over an intermediate pressure regime a mixed mode of failure mechanisms is observed. Furthermore, the micromechanical roots of the model allow the effects on localized deformation modes of various initial microstructures to be studied. The results obtained from both the constitutive responses and BVP solutions indicate that the proposed approach and model provide a promising basis for future theoretical studies on cemented granular materials. (C) 2014 Elsevier Ltd. All rights reserved.
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| 4. |
- Etxegarai, Maddi, et al.
(författare)
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Characterisation of single-phase fluid-flow heterogeneity due to localised deformation in a porous rock using rapid neutron tomography
- 2021
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Ingår i: Journal of Imaging. - : MDPI AG. - 2313-433X. ; 7:12
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Tidskriftsartikel (refereegranskat)abstract
- The behaviour of subsurface-reservoir porous rocks is a central topic in the resource engineering industry and has relevant applications in hydrocarbon, water production, and CO2 sequestration. One of the key open issues is the effect of deformation on the hydraulic properties of the host rock and, specifically, in saturated environments. This paper presents a novel full-field data set describing the hydro-mechanical properties of porous geomaterials through in situ neutron and X-ray tomography. The use of high-performance neutron imaging facilities such as CONRAD-2 (Helmholtz-Zentrum Berlin) allows the tracking of the fluid front in saturated samples, making use of the differential neutron contrast between “normal” water and heavy water. To quantify the local hydro-mechanical coupling, we applied a number of existing image analysis algorithms and developed an array of bespoke methods to track the water front and calculate the 3D speed maps. The experimental campaign performed revealed that the pressure-driven flow speed decreases, in saturated samples, in the presence of pre-existing low porosity heterogeneities and compactant shear-bands. Furthermore, the observed complex mechanical behaviour of the samples and the associated fluid flow highlight the necessity for 3D imaging and analysis.
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| 5. |
- Guillaume, Florian, et al.
(författare)
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Neutron microtomography to investigate the bone-implant interface - Comparison with histological analysis
- 2021
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 66:10
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Tidskriftsartikel (refereegranskat)abstract
- Bone properties and especially its microstructure around implants are crucial to evaluate the osseointegration of prostheses in orthopaedic, maxillofacial and dental surgeries. Given the intrinsic heterogeneous nature of the bone microstructure, an ideal probing tool to understand and quantify bone formation must be spatially resolved. X-ray imaging has often been employed, but is limited in the presence of metallic implants, where severe artifacts generally arise from the high attenuation of metals to x-rays. Neutron tomography has recently been proposed as a promising technique to study bone-implant interfaces, thanks to its lower interaction with metals. The aim of this study is to assess the potential of neutron tomography for the characterisation of bone tissue in the vicinity of a metallic implant. A standardised implant with a bone chamber was implanted in rabbit bone. Four specimens were imaged with neutron tomography and subsequently compared to non-decalcified histology to stain soft and mineralised bone tissues, used here as a ground-truth reference. An intensity-based image registration procedure was performed to place the 12 histological slices within the corresponding 3D neutron volume. Significant correlations (p < 0.01) were obtained between the two modalities for the bone-implant contact (BIC) ratio (R = 0.77) and the bone content inside the chamber (R = 0.89). The results indicate that mineralised bone tissue can be reliably detected by neutron tomography. However, the BIC ratio and bone content were found to be overestimated with neutron imaging, which may be explained by its sensitivity to non-mineralised soft tissues, as revealed by histological staining. This study highlights the suitability of neutron tomography for the analysis of the bone-implant interface. Future work will focus on further distinguishing soft tissues from bone tissue, which could be aided by the adoption of contrast agents.
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| 6. |
- Lewis, Helen, et al.
(författare)
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Interactions Between Imbibition and Pressure-Driven Flow in a Microporous Deformed Limestone
- 2023
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Ingår i: Transport in Porous Media. - : Springer Science and Business Media LLC. - 0169-3913 .- 1573-1634. ; 146:3, s. 559-585
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Tidskriftsartikel (refereegranskat)abstract
- Neutron imaging is used for direct observation of evolving water–air and deuterated water–normal water exchanges in flow experiments performed on a laboratory-deformed, microporous laminated limestone, an extremely fine-textured rock altered by arrays of superposed fractures generated in a rock mechanics apparatus. The neutron images document significant, evolving, water speed and flow direction variability at the deci-micron scale and spatially complex patterns of both increasing and decreasing water saturation. We infer that capillarity-driven and pressure-driven water movement occurs concurrently, in close proximity and in competition, and that as local and global water saturations evolve these two drivers can change their dominance in both matrix and deformed elements. Thin sections are used to obtain sub-micron resolution SEM images that provide multi-scale information on the textural features’ spatial arrangements. The textural characteristics are consistent with the inferences made from the coarser flow imaging. Alternating lamina types provide the primary lithological heterogeneity, while the experimentally created deformations lead to quasi-planar zones of highly comminuted matrix and fracture-like voids, each with lengths ranging from sub-mm to cm. Together deformation features delineate a partially connected array. The interplay between fluid movement through deformation features, and flow into (and out of) the laminae, implies near-equivalence of local driving pressure- and capillary-related energies, with subtle shifts in this balance as water saturation increases. The insights gained invite a re-examination of common rules-of-thumb for multi-phase fluid flow often adopted in fractured, low-permeability microporous rocks.
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| 7. |
- Lindblom, David, et al.
(författare)
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In-situ neutron imaging of delayed hydrogen cracking in highstrength steel - experiments and modeling
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Recension (övrigt vetenskapligt/konstnärligt)abstract
- Hydrogen delayed fracture, also known as hydrogen-induced cracking, is a type of brittle fracture that occurs due to the slow diffusion and accumulation of hydrogen atoms, leading todecreased ductility and eventual cracking under constant load. This paper presents an in-situobservation, using neutron imaging, of delayed crack propagation caused by hydrogen embrittlement in a high strength martensitic steel specimen. The experiments involved mechanicalloading of a single-edge-notch bend specimen while submerged in an electrolyte solution (H2O+ 3.5% NaCl) under cathodic polarization to facilitate hydrogen ingress. Neutron transmission images were obtained in-situ and used to monitor intermittent crack propagation wasrecorded over a period of 12 hours. The stress state at each crack configuration was extracted from a three-dimensional elastic-plastic finite element simulation, which was tailoredto match the quantitative information acquired from the neutron radiographs of the fractureprocess. To gain insight into the evolution of hydrogen concentration with crack propagation,a modeling scheme for stress-assisted hydrogen diffusion was employed. These simulationsprovided qualitative information on the relation between intermittent crack propagation andthe subsequent supply of hydrogen to the crack tip. Finally, a failure locus was constructedbased on the calculated hydrogen concentration levels and the experimentally determinedcrack growth resistance.
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| 8. |
- Markeviciute, Vetra, et al.
(författare)
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Systemically administered zoledronic acid activates locally implanted synthetic hydroxyapatite particles enhancing peri-implant bone formation : A regenerative medicine approach to improve fracture fixation
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Ingår i: Acta Biomaterialia. - 1742-7061.
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Tidskriftsartikel (refereegranskat)abstract
- Fracture fixation in an ageing population is challenging and fixation failure increases mortality and societal costs. We report a novel fracture fixation treatment by applying a hydroxyapatite (HA) based biomaterial at the bone-implant interface and biologically activating the biomaterial by systemic administration of a bisphosphonate (zoledronic acid, ZA). We first used an animal model of implant integration and applied a calcium sulphate (CaS)/HA biomaterial around a metallic screw in the tibia of osteoporotic rats. Using systemic ZA administration at 2-weeks post-surgery, we demonstrated that the implant surrounded by HA particles showed significantly higher peri‑implant bone formation compared to the unaugmented implants at 6-weeks. We then evaluated the optimal timing (day 1, 3, 7 and 14) of ZA administration to achieve a robust effect on peri‑implant bone formation. Using fluorescent ZA, we demonstrated that the uptake of ZA in the CaS/HA material was the highest at 3- and 7-days post-implantation and the uptake kinetics had a profound effect on the eventual peri‑implant bone formation. We furthered our concept in a feasibility study on trochanteric fracture patients randomized to either CaS/HA augmentation or no augmentation followed by systemic ZA treatment. Radiographically, the CaS/HA group showed signs of increased peri‑implant bone formation compared with the controls. Finally, apart from HA, we demonstrated that the concept of biologically activating a ceramic material by ZA could also be applied to β-tricalcium phosphate. This novel approach for fracture treatment that enhances immediate and long-term fracture fixation in osteoporotic bone could potentially reduce reoperations, morbidity and mortality. Statement of significance: • Fracture fixation in an ageing population is challenging. Biomaterial-based augmentation of fracture fixation devices has been attempted but lack of satisfactory biological response limits their widespread use. • We report the biological activation of locally implanted microparticulate hydroxyapatite (HA) particles placed around an implant by systemic administration of the bisphosphonate zoledronic acid (ZA). The biological activation of HA by ZA enhances peri‑implant bone formation. •Timing of ZA administration after HA implantation is critical for optimal ZA uptake and consequently determines the extent of peri‑implant bone formation. • We translate the developed concept from small animal models of implant integration to a proof-of-concept clinical study on osteoporotic trochanteric fracture patients. • ZA based biological activation can also be applied to other calcium phosphate biomaterials.
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| 9. |
- Martell, Josefin, et al.
(författare)
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The scale of a martian hydrothermal system explored using combined neutron and x-ray tomography
- 2022
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 8:19
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Tidskriftsartikel (refereegranskat)abstract
- Nakhlite meteorites are igneous rocks from Mars that were aqueously altered ~630 million years ago. Hydrothermal systems on Earth are known to provide microhabitats; knowledge of the extent and duration of these systems is crucial to establish whether they could sustain life elsewhere in the Solar System. Here, we explore the three-dimensional distribution of hydrous phases within the Miller Range 03346 nakhlite meteorite using nondestructive neutron and x-ray tomography to determine whether alteration is interconnected and pervasive. The results reveal discrete clusters of hydrous phases within and surrounding olivine grains, with limited interconnectivity between clusters. This implies that the fluid was localized and originated from the melting of local subsurface ice following an impact event. Consequently, the duration of the hydrous alteration was likely short, meaning that the martian crust sampled by the nakhlites could not have provided habitable environments that could harbor any life on Mars during the Amazonian.
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| 10. |
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