| 1. |
- Aderemi, Adetomiwa, et al.
(författare)
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Porosity and permeability calculations in a Biolithite using x-ray tomography images
- 2023
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Ingår i: SEG Technical Program Expanded Abstracts. - 1052-3812. ; 2023-August, s. 1700-1704
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Forskningsöversikt (refereegranskat)abstract
- Engineering energy storage/extraction for geoenergy applications (e.g., geothermal energy extraction, CO2 and/or Hydrogen storage) requires a very good knowledge of subsurface heterogeneities. One of the principal factors that influences the response of the underground system is the continuously evolving pore networks of the targeted rocks. This work aims to understand the pore network of a natural Biolithite (Figure 1), coming from a Greek outcrop, and to predict the permeability of lab-scale systems (due to diagenetic alterations and/or natural deformation) using x-ray computed tomography (CT) images (3D) and stochastic model reconstructions. We emphasize on the importance of a reproducible image analysis workflow (Figure 2) during reservoir description, as an input to extracting pore network models that have representative geometrical and topological characteristics at core-plug scale.
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| 2. |
- Borgqvist, Eric, et al.
(författare)
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Localized Deformation in Compression and Folding of Paperboard
- 2016
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Ingår i: Packaging Technology & Science. - : Wiley. - 0894-3214. ; 29:7, s. 397-414
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Tidskriftsartikel (refereegranskat)abstract
- The localized deformation patterns developed during in-plane compression and folding of paperboard have been studied in this work. X-ray post-mortem images reveal that cellulose fibres have been reoriented along localized bands in both the compression and folding tests. In folding, the paperboard typically fails on the side where the compressive stresses exists and wrinkles are formed. The in-plane compression test is however difficult to perform because of the slender geometry of the paperboard. A common technique to determine the compression strength is to use the so-called short-span compression test (SCT). In the SCT, a paperboard with a free length of 0.7 mm is compressed. Another technique to measure the compression strength is the long edge test where the motion of the paperboard is constrained on the top and bottom to prevent buckling. A continuum model that previously has been proposed by the authors is further developed and utilized to predict the occurrence of the localized bands. It is shown that the in-plane strength in compression for paperboard can be correlated to the mechanical behaviour in folding. By tuning the in-plane yield parameters to the SCT response, it is shown that the global response in folding can be predicted. The simulations are able to predict the formation of wrinkles, and the deformation field is in agreement with the measured deformation pattern. The model predicts an unstable material response associated with localized deformation into bands in both the SCT and folding.
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| 3. |
- Butt, Awais, et al.
(författare)
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Applicability of ultrasonic tomographic technique for progressive damage evaluation in prismatic rock specimen
- 2019
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Konferensbidrag (refereegranskat)abstract
- Several damage processes are associated with the loading of intact rock specimens including closure of existing microcracks, initiation of cracks, and finally development of cracks. Ultrasonic imaging techniques have proven to be very successful in providing relatively high-resolution images of the damage processes in the rock. Ultrasonic velocity tomography is a full-field measurement technique that can help understand the evolution of damage within a brittle rock specimen remotely and non-destructively. Variations in elastic compressional (P-) wave velocity in a rock specimen can be associated with the changes in its elastic properties under mechanical loading at different stages of damage. The objective of this research study was to examine the applicability of ultrasonic tomographic technique for determination of velocity fields in prismatic rock specimens subjected to uniaxial compression. An array of piezoelectric ultrasonic sensors were used to generate and receive elastic waves across the prismatic specimen and a fast LabVIEW-based data acquisition system was used to record the waveforms. By analyzing and comparing the changes in generated velocity tomograms, through tomographic inversion method, the velocity fields in synthetic and natural rocks were determined.
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| 4. |
- Butt, Awais, et al.
(författare)
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Evaluation of progressive damage in barre granite using ultrasonic velocity tomography and digital image correlation
- 2020
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Ingår i: 54th U.S. Rock Mechanics/Geomechanics Symposium. - 9780979497551
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Konferensbidrag (refereegranskat)abstract
- Full-field measurement techniques have the significant advantage of taking measurements along the complete specimen specially assisting in the characterization of heterogeneous rocks. This research's objective was therefore to evaluate and characterize the damage occurring inside uniaxially-loaded Barre granite specimens using two non-destructive full-field measurement techniques, namely, the ultrasonic velocity tomography (UVT) and two-dimensional digital image correlation (2D-DIC). Piezoelectric ultrasonic sensors were used to generate and receive elastic P-waves across the prismatic specimen and a fast LabVIEWbased data acquisition system was used to record the waveforms. Ultrasonic tomographic inversion method was utilized to generate sectional velocity field tomograms, at different levels of uniaxial stress compared to the failure stress level. By analyzing and comparing the changes in velocity tomograms, the initiation and growth of cracking in the rock specimens were monitored. The low-velocity zones in the tomograms were associated with the location and extent of damage in the specimen. The 2D-DIC technique was used to determine the displacement and strain across the specimen surface by analyzing the digital images acquired during the uniaxial loading. 2D-DIC was able to identify the damage occurring in the form of crack formation and propagation and highlighted the importance of using combined full-field measurement techniques.
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| 5. |
- 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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| 6. |
- Finegan, Donal P, et al.
(författare)
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Quantifying Bulk Electrode Strain and Material Displacement within Lithium Batteries via High-Speed Operando Tomography and Digital Volume Correlation
- 2015
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Ingår i: Advanced Science. - : Wiley. - 2198-3844.
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Tidskriftsartikel (refereegranskat)abstract
- Tracking the dynamic morphology of active materials during operation of lithium batteries is essential for identifying causes of performance loss. Digital volume correlation (DVC) is applied to high-speed operando synchrotron X-ray computed tomography of a commercial Li/MnO2 primary battery during discharge. Real-time electrode material displacement is captured in 3D allowing degradation mechanisms such as delamination of the electrode from the current collector and electrode crack formation to be identified. Continuum DVC of consecutive images during discharge is used to quantify local displacements and strains in 3D throughout discharge, facilitating tracking of the progression of swelling due to lithiation within the electrode material in a commercial, spiral-wound battery during normal operation. Displacement of the rigid current collector and cell materials contribute to severe electrode detachment and crack formation during discharge, which is monitored by a separate DVC approach. Use of time-lapse X-ray computed tomography coupled with DVC is thus demonstrated as an effective diagnostic technique to identify causes of performance loss within commercial lithium batteries; this novel approach is expected to guide the development of more effective commercial cell designs.
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