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Computed tomography system with strict real-time synchronization for in-situ 3D analysis of periodically vibrating objects
Rada, Václav ; Fíla, Tomáš ; Zlámal, Petr ; Koudelka_ml., Petr ; Šleichrt, Jan ; Macháček, Michael ; Vavřík, Daniel ; Kytýř, Daniel
In the contribution, we present a laboratory system capable of X-ray computed tomography (XCT) scanning of an periodically moving or oscillating object. The system is an in-house developed XCT setup with electromagnetic voice coil actuator mounted on top of the rotary stage of the setup. The strict synchronization of the components, the rotary stage, the electromagnetic actuator movement and the detector readout is accomplished with use of the detector hardware trigger and hard real-time Linux operating system. Cylindrical sample manufactured from epoxy resin with metal particles to enable movement tracking is scanned in a stationary position and during periodical movement induced by the vibration stage. The volumetric data of the scans is compared and the results of this contribution represent an important step towards identification of defects through modal analysis of in-situ harmonically vibrating object.
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Tomographic investigation of the sandstone fracture toughness
Vavřík, Daniel ; Beneš, Pavel ; Fíla, Tomáš ; Koudelka_ml., Petr ; Kumpová, Ivana ; Vavro, Martin
It is well known that the measured values of the fracture toughness of quasi brittle materials are influenced by material heterogeneity, dimensions, boundary conditions, and unequal tension and compression properties. Standard testing methods supposing isotropic material, in contrary the quasi-brittle materials differ from this theoretical expectation, therefore this approach may fail. The authors present Local Fracture Toughness Testing (LFTT) method to overcome this obstacle. LFFT based on a complex methodology using a series of tomographic reconstructions recorded during specimen loading is calculated independently of the outside boundary conditions.
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The method of conservation, preservation, and restoration of subjects of cultural heritage on the ceramic basis (fired/unfired clay)
Štefcová, P. ; Kadeřábková, J. ; Polák, L. ; Valach, Jaroslav ; Vavřík, Daniel
The ceramic (decorative or utility) accompanies humanity from prehistoric times to the present days. Therefore, ceramic play important role in collections in all institutions. Due to the nature of the material are those items extremely sensitive to mechanical damage. The submitted method explains the damage mechanism or destruction of the items of cultural heritage. The method also summarizes recommendations for designing the optimal condition of depositing, exhibiting, conservation/restoration, and the manipulation with such sensitive material. Including a description of several methods useful to make quality documentation and replication of cultural heritage items (3D models). \n
Plný tet:  PDF
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The method of conservation, preservation and restoration of subjects of cultural heritage on the ceramic basis (fired/unfired clay)
Štefcová, Petra ; Kadeřábková, Jana ; Polák, Ladislav ; Valach, Jaroslav ; Vavřík, Daniel
The ceramic (decorative or utility) accompanies humanity from prehistoric times to the present days. Therefore, the ceramic play important role in collections in all institutions. Due to the nature of the material are those items extremely sensitive to mechanical damage. The submitted method explains the damage mechanism or destruction of the items of cultural heritage. The method also summarizes recommendations for designing the optimal condition of depositing, exhibiting, conservation/restoration, and the manipulation with such sensitive material. Including a description of several methods useful to make quality documentation and replication of cultural heritage items (3D models).
Fulltext: PDF
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Possibilities of using 4D computed tomography in fracture tests
Kumpová, Ivana ; Fíla, Tomáš ; Koudelka, Petr ; Rozsypalová, I. ; Keršner, Z. ; Kytýř, Daniel ; Vopálenský, Michal ; Vavřík, Daniel ; Vyhlídal, M. ; Drdácký, Miloš
The paper presents the study of the internal structure and fracture properties of selected quasi-brittle building materials subjected to temperature changes and the possibility of applying the method combining bending fracture tests and time-dependent computed tomography (4D CT). The tested specimens were subjected to hightemperature effects and subsequently tested by a four-point bending during 4D CT. Thus, 3D image information was obtained in different phases of loading and material damage. Comparative compression strength measurements were also performed. These results are in good agreement
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Analysis of Baroque sculpture based on X-ray fluorescence imaging and X-ray\ncomputed tomography data fusion
Vavřík, Daniel ; Kumpová, Ivana ; Vopálenský, Michal ; Lauterkranc, J.
It is advantageous to combine information about geometry and the inner structure of historical artifacts with information about the elemental composition of decorative layers, typically covering historical wooden sculptures. X-ray computed tomography describing artifact structure is quite common and easy. Standard X-ray fluorescence (XRF) analysis of decorative layers is typically done for several selected spots of the artifact’s surface utilizing single pad detector. XRF imaging fully describing the surface’s elemental composition is commonly done for flat objects, while time consuming XRF tomography is applied to relatively small objects. It will be shown in this work that an effective fusion combination of XRF imaging and X-ray tomography describing the whole object can be realized even when using a limited number of XRF images.
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Three-dimensional characterization of polymer foams using X-ray dark-field imaging
Senck, S. ; Plank, B. ; Gusenbauer, C. ; Salaberger, D. ; Vavřík, Daniel ; Santer, W. ; Kastner, J.
Due to the low cost, the ease of processing, and excellent material properties, polymer foams are used in various applications, e.g. packaging, building and construction, furnitures and bedding, and the automotive and aerospace sector. The mechanical response of polymer foams is primarily influenced by density and morphology. While foam density can be determined with high precision, cell morphology is more difficult to determine since the size distribution of foam cells differs in three dimensions. However, using conventional methods, e.g. optical light microscopy or scanning electron microscopy, it is very difficult to obtain three-dimensional information and to differentiate between the strut system and cell walls. An alternative for the three-dimensional characterization of foam morphology is micro-computed tomography (XCT). But even non-destructive techniques like XCT are not able to characterize anisotropic foams if the thickness of single struts and cell walls is below the physcial resolution of the respective XCT system. In this contribution we therefore investigate different polymeric foam samples using a Talbot-Lau grating interferometer XCT (TLGI-XCT) system. We show that the obtained darkfield contrast images show a high contrast and a strong signal at struts and cell walls, facilitating the segmentation of foam cells in various examples.
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Optimization of acquisition parameters in radiography and tomography
Vopálenský, Michal ; Vavřík, Daniel ; Kumpová, Ivana
Contrast in radiographic images is one of the most important parameters both in radiography and tomography. This paper investigates the possibility of adjusting the radiographic parameters, in particular the accelerating voltage of the X-ray tube, in order to maximize the difference in the detected intensity in response to the change in the thickness of the investigated object. Simplified model is used that allows finding the optimal operating point for the given material and thickness without an apriory knowledge about the X-ray spectra, detector response and the material composition. It is shown that in case of small changes of thickness, the optimum is met when the detected intensity behind the object of certain thickness is at approx. 37 % of the full range (i.e., of the value that would be measured under the same conditions in the absence of the object). In spite of simplifications made, the theoretical model shows a very good correspondence with the experimental data. A brief consideration is made on the case of a general difference in thicknesses.
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Concrete with steel reinforcement
Kumpová, Ivana ; Jandejsek, Ivan ; Vavřík, Daniel
The work was focused on X-Ray tomography and creating of 3D computer models of ten concrete samples with various steel reinforcement contents and different production technology. From these models, the volume ratios of individual components (concrete: reinforcement: pores) and directional layout of individual fibers were calculated.
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Long bone measurements
Kumpová, Ivana ; Vavřík, Daniel
The work was focused on X-Ray tomography and creating of 3D computer models of historically valuable long bones. Selected slices of reconstructed data in 50% and 35% of each bone length and the entire 3D reconstructions of all specimens, were stored on the supplied medium in DICOM format and forwarded to the client representative together with an extensive measurement protocol.
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