National Repository of Grey Literature 32 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Analysis of the porosity of a plaster cast, based on tomography data. Pilot measurement for the feasibility verification of the method for analyses of cast sculptures
Kumpová, Ivana ; Vopálenský, Michal
The aim of the tomographical research was the verification of the feasibility of the X-ray tomography for the qualitative description of the internal structure of the cast sculptures (damage, former restoration evidence etc.) and also for the characterization of the way and direction of the plaster pouring. There is a hypothesis that in the cast piece, the non-uniform distribution of pores as for the size (volume) along the vertical direction should be observable. The deeper in the piece, the higher amount of smaller pores and lower amount of bigger pores is expected. As well, lower porosity, i.e., ratio of the volume of the pores and the entire investigated volume, is expected deeper in the sample. The distribution of the pores could indicate, how the sculpture was made, in particular, where were the pouring holes and how many, what was the material flux like and how did it mixture. The method was verified on a specimen and the indicated hypotheses were only partly confirmed.
Region of interest tomography
Vopálenský, Michal ; Kumpová, Ivana
During standard tomographic process, the acquisition of tomographic data (projections) is performed with geometric adjustment of the tomographic assembly ensuring that the projection of the entire width of the examined object fits onto the detector during the full object rotation. Because of the limited width of the detector, this approach has a limited maximum achievable resolution for the given specimen diameter. It is possible to make higher magnification, but then the projections do not fit onto the detector, which causes certain problems during the reconstruction, but allows achieving of higher resolution in the always-visible region of the object (the region of interest). The research was focused on evaluation of ROI tomography approach on the TORATOM tomograph.
Tomography of a bronze axe of the Únětice culture, found in Kukleny, Hradec Králové
Kumpová, Ivana ; Vopálenský, Michal
It has been shown in the past that the computed X-ray tomography can bear significant new findings on the distribution of damaging and other structural details of the bronze findings. However, relatively high beam energies are necessary and it is not a priori ensured that the object under test would be penetrated with the radiation sufficiently. A big problem is also the photon scattering, which can make fine details indistinguishable. Therefore, a chosen Únětice culture axe has been submitted to a tomographical investigation in the laboratory of X-ray tomography of the Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences, v.v.i. The result should confirm the suitability of the method for investigations of other similar bronze findings.
Scientific report. Sps_025: Ceramics B4C + 1Ti, 1800°C, 2 min
Kumpová, Ivana ; Vopálenský, Michal
The aim of the measurement was to verify the feasibility of 3D computed tomography for observing structural details in samples of B4C - Ti ceramics with 1 % of Ti. Sample designated Sps_025: Keramika B4C + 1Ti, 1800°C, 2 min, in the form a cylinder with the diameter of 12 mm and the height of 10 mm was investigated by this method.
X-ray micro-tomography characterization of voids caused by three-point bending in selected alkali-activated aluminosilicate composite
Kumpová, Ivana ; Rozsypalová, I. ; Keršner, Z. ; Rovnaníková, P. ; Vopálenský, Michal
This paper deals with the pilot characterization of a special alkali-activated aluminosilicate composite composed of waste brick powder, brick rubble and a solution of potassium water glass. Fracture tests were conducted on the specimens via three-point bending and fracture parameters were evaluated. Selected specimen was investigated using micro-tomography to supplement the results with visual information about the inner structure of this newly designed material before and after the mechanical loading. Tomographic measurements and image processing were conducted for a qualitative and quantitative assessment of changes in the internal structure with an emphasis on the calculation of porosimetric parameters and visualization of the fracture surface. Fractal dimension of fracture surface was estimated.
Evaluation of self-healing in concrete by means of analytical techniques
Aspiotis, K. ; Sotiriadis, Konstantinos ; Kumpová, Ivana ; Mácová, Petra ; Badogiannis, E. ; Tsivilis, S.
In the present work, the self-healing process in concrete was evaluated using analytical techniques. For this purpose, two concrete mixes of different composition (one used as reference) were prepared with a W/B of 0.45. The self-healing process was triggered by the introduction in the concrete mix of a commercial expansive admixture (calcium sulfo-aluminate), two dicarboxylic acids, and sodium carbonate salt. After 28 days curing in water, the specimens were artificially cracked (crack width ≈ 400 μm) and then again water-cured for 40 days until self-healing occurred. The progress of self-healing was investigated with a stereo-microscope at 40, 50 and 60 days. The efficiency of the process was evaluated using micro-Raman spectroscopy and X-ray micro-computed tomography (XmCT). Significant reduction in the crack width was observed as a result of filling the crack with calcite generated during the self-healing process. In some cases, the crack was completely healed. The experimental methodology used provided new insights into the evolution of the self-healing phenomenon in concrete.
Fracture Parameters of AAAS composites with ceramic precursor
Šimonová, H. ; Rozsypalová, I. ; Kumpová, Ivana ; Trčka, T. ; Frantík, P. ; Rovnaníková, P. ; Keršner, Z.
The paper deals with alkali-activated aluminosilicate composites based on ceramic precursors with respect to their characterization by fracture-mechanical parameters. Three composites made of brick dust as a precursor and alkaline activator with silicate modulus Ms = 1.0, 1.2 and 1.4 were investigated. After 28 days of maturation, specimens with nominal dimensions of 40 × 40 × 160 mm were provided by an initial notch to 1/3 of the body height in the middle of the span. At least 6 samples were tested from each composite. Specimens were subjected to three-point bending tests during which force vs. deflection at midspan (F–d) and force vs. crack mouth opening displacement (F–CMOD) diagrams were recorded. By processing these diagrams, the values of the static modulus of elasticity, the effective fracture toughness (including its initiating component) and the specific fracture energy were determined using the effective crack model, Work-of-Fracture method, and Double-K fracture model. After the fracture experiments had been performed, compressive strength values were determined for informational purposes from one part of each specimen that remained after testing. All evaluations included the determination of arithmetic means and standard deviations. To obtain information about the internal structure of composites before and after mechanical testing, the selected body was examined by micro-tomography. Tomographic measurements and image processing were performed for qualitative and quantitative evaluation of internal structure changes with an emphasis on the calculation of porosimetric parameters as well as visualization of the fracture process zone. The fractal dimension of fracture objects was determined.
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
Large-area scans of paintings with high resolution
Vopálenský, Michal ; Kumpová, Ivana
The aim of the measurement was to obtain the radiographs from historical paintings from the Faculty of Restoration of the University Pardubice. Due to the dimensions of the paintings (up to 90 x 110 cm) it was necessary to develop a suitable measurement procedure for successive scanning of the paintings in the TORATOM device. The resulting data are important for the planning of the restoration processes of the paintings and can help to discover otherwise invisible details, like underpaintings etc.
Tomographical investigation of the historical metal bracelets
Kumpová, Ivana ; Vopálenský, Michal
The work was focused on the method definition for the investigation of historical metal artifacts employing the X-ray tomography. Two metal bracelets made of brass and plated with silver were investigated in the laboratory. The goal was to determine the technology of manufacturing and damages, possible also to visualize the silver layer.

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21 KUMPOVÁ, Ivana
1 Kumpová, I.
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