National Repository of Grey Literature 20 records found  1 - 10next  jump to record: Search took 0.01 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.
Quantification of microstructural changes in limestone cement paste stored in sulfate environment at low temperature
Sotiriadis, Konstantinos ; Hlobil, Michal ; Machová, Dita ; Mácová, Petra ; Viani, Alberto ; Vopálenský, Michal
Samples of cement paste based on mixed cement with limestone admixture were stored in a magnesium sulfate solution for 6 months at 5 ° C to monitor the development of sulfate corrosion and its effect on microstructure. The extent of corrosion was evaluated by several different techniques. The paste samples were scanned at monthly intervals by X-ray tomography for non-destructive quantification of the pore structure and extent of damage, along with a description of the phase changes in the microstructure using X-ray diffraction and infrared spectroscopy. Compressive strength testing confirmed the effect of corrosion on the mechanical resistance of the samples. The results show a rapid course of degradation propagating in an irregular band, caused primarily by the formation of expandable sulfur-based corrosion products, the consequent crack formation and loss of internal cohesion of the material. The occurrence of both ettringite and thaumasite and gypsum was confirmed in the damaged parts.
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.
Historical lingerie: 18th century corset
Kumpová, Ivana ; Vopálenský, Michal
The work was focused on the methodology using X-ray tomographical imaging for the exploration of the textile-based historical artifacts. The 18th-century corset was investigated by this method. The inspection was conducted to reveal the production technology, design solution, decoration and possible damage in the front area where the whalebones converge. The computed tomography performed on the TORATOM device enabled visualisation of the internal structure of the area of interest with high precision. Sewing details and details of the composition of different material layers are well visible. Fractures and frayed ends of the whalebones were observed. In the area of interest, it is possible to distinguish several materials used for padding of the plastic parts.

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