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106 results on '"Kytýř, Daniel"'

3. Damage Localisation in Fresh Cement Mortar Observed via In Situ (Timelapse) X-ray {\mu}CT imaging

Author

Miarka, Petr, Kytýř, Daniel, Koudelka, Petr, and Bílek, Vlastimil

Subjects
Condensed Matter - Materials Science
Abstract

This paper presents the outcome of a study focused on the evolution of internal damage in fresh cement mortar over 25 hours of hardening. In situ timelapse X-ray computed micro-tomography ({\mu}XCT) imaging method was used to detect internal damage and capture its evolution in cement mortar hardening. During {\mu}XCT scans, the temperature released during the cement hydration was measured, which provided insight into the internal damage evolution with a link to a hydration temperature rise. The measured temperature during cement mortar hardening was compared with an analytical model, which showed a relatively good agreement with the experimental data. Using 20 CT scans acquired throughout the observed cement mortar hardening, it was possible to obtain a quantified characterisation of the porous space. Additionally, the use of timelapse {\mu}XCT imaging over 25 hours allowed for studying the crack growth inside the meso-structure including its volume and surface characterisation. The results provide valuable insights into cement mortar shrinkage and serve as a proof-of-concept methodology for future material characterisation.

Published
2024
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8. Novel Device for 4-Point Flexural Testing of Quasi-Brittle Materials During 4D Computed Tomography

Author

Koudelka, Petr, Fíla, Tomáš, Kytýř, Daniel, Vavro, Leona, Vavro, Martin, Souček, Kamil, Vavřík, Daniel, Drdácký, Miloš, Correia, José A.F.O., Series Editor, De Jesus, Abílio M.P., Series Editor, Ayatollahi, Majid Reza, Advisory Editor, Berto, Filippo, Advisory Editor, Fernández-Canteli, Alfonso, Advisory Editor, Hebdon, Matthew, Advisory Editor, Kotousov, Andrei, Advisory Editor, Lesiuk, Grzegorz, Advisory Editor, Murakami, Yukitaka, Advisory Editor, Carvalho, Hermes, Advisory Editor, Zhu, Shun-Peng, Advisory Editor, and Gdoutos, Emmanuel E., editor

Published
2019
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9. DESIGN OF THE TESTING PROCEDURE FOR INVESTIGATION OF ERYX CONICUS DERMAL ARMOUR CHARACTERISTICS.

Author

ŽALOUDKOVÁ, BLANKA, KOUDELKA, PETR, FRÝDLOVÁ, PETRA, DROZDENKO, MYKHAILO, ŠLEICHRT, JAN, and KYTÝŘ, DANIEL

Subjects
SNAKES, COMPUTED tomography, STRESS-strain curves, X-rays, COMPRESSION loads
Abstract

The aim of this work is to develop an experimental method suitable for the mechanical testing of highly non-standard biological samples such as snake skin with osteoderms. The objective of the method is to determine, whether the osteoderms provide a protective function for the animal in its natural environment. For this purpose, a simulation of rodents biting the skin based on uni-axial compressive loading using a synthetic tooth as a penetrator was developed with an emphasis on integration with X-ray scanners to facilitate in-situ testing. To identify and characterise the structure of snake skin and to prove the protective function of osteoderms, all samples were subjected to high resolution X-ray computed tomography. The results of the experiments are presented in the form of stress-strain curves and a map of the tangent modulus. [ABSTRACT FROM AUTHOR]

Published
2024
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20. Experimental study of dynamic periodic processes

Author

Vavřík, Daniel, Fila, Tomáš, Koudelka, Petr, Rada, Václav, Macháček, Michael, Zlámal, Petr, and Kytýř, Daniel

Abstract

In the field of experimental mechanics, X-ray computed tomography is a well-established method for non-destructive testing of a wide range of objects. It is quite common to employ digital volumetric correlation to evaluate the deformation of bodies by comparing their initial and current state. Time-dependent tomography, which works with tomographic data sets covering the entire process under investigation, has also been on the rise in recent years. However, we must keep in mind that a single tomographic data set represents thousands of X-ray images, making such measurements quite demanding in terms of instrumentation and subsequent data processing. For events taking minutes or longer, conventional laboratory X-ray computed tomography scanner can be used, while for faster events a very intense X-ray source is usually required, which typically leads to the use of a synchrotron. From a particular speed, even synchrotron sources may no more be enough. An exception is tomographic tracking of purely periodic events, such as the oscillation of a beam at its natural frequency. As will be shown, despite the relatively high velocity of motion, a good reconstruction can be achieved even with a conventional X-ray source. Thus, we obtain information not only about the intrinsic shape of a particular beam, but also about its internal structure. It will be possible, for example, to investigate how any local imperfections may affect the shape of the vibration, assuming that some defects may not be apparent under static loading. Specifically, this paper will show the results of a tomographic reconstruction of a slender beam oscillating at 4.15 Hz.

Published
2025
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21. 4D XCT inspection of the preserved sandstone subjected to compression loading

Author

Kytýř, Daniel, Zárybnická, Lucie, Zlámal, Petr, Koudelka, Petr, Machotová, Jana, Šleichrt, Jan, and Ševčík, Radek

Abstract

Deep preservation of natural sandstone could significantly slow down the degradation processes in sandstone used for both civil engineering and decorative purposes. Chemical conservation completely changes the overall deformation characteristics when the material no longer exhibits brittle behavior. For better understanding of the deformation processes on micro level of individual grains, a time-lapse X-ray computed tomography compression experiment followed by digital volume correlation evaluation of displacement fields was performed on Obernkirchen sandstone as a typical representative of the building and sculpture material. Detailed full-field information on the deformation behavior of the consolidated sandstone helps to better understand how the consolidants increase the resilience of the sandstone at the micro-level, primarily in the field of conservation science.

Published
2025
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23. CHARACTERISATION OF THERMAL-LOADED CEMENT-BASED COMPOSITES BY COMBINED TIME-LAPSE TOMOGRAPHY AND THE FOUR-POINT BENDING TEST

Author

Kumpová, Ivana, Fíla, Tomáš, Koudelka, Petr, Rozsypalová, Iva, Keršner, Zbyněk, Kytýř, Daniel, Vopálenský, Michal, Vavřík, Daniel, Kumpová, Ivana, Fíla, Tomáš, Koudelka, Petr, Rozsypalová, Iva, Keršner, Zbyněk, Kytýř, Daniel, Vopálenský, Michal, and Vavřík, Daniel

Abstract

Quasi-brittle materials like cement-based composites, rocks, and bricks are subjected to a number of environmental loadings throughout the life cycle of buildings. For instance, fluctuation of the ambient temperature (climatic cycles or fire) causing a variety of physical and chemical transitions resulting in structural changes and affecting the mechanical properties. In this work a special mixture containing glass spheres and Portland cement was evaluated by a combination of four-point bending and time-lapse X-ray computed tomography to verify the feasibility of this novel combined method. The effect of temperature on the behavior of investigated material in terms of sphericity of the present glass spheres and the way of crack propagation under load together with its influence to mechanical fracture parameters was studied. The described methodology was used especially to be able to monitor these changes throughout the loading process, as the characterization of the fracture surface using conventional optical methods is possible only after the complete fracture of the specimen and total damage of used material results in loosening of the matrix and filler to such an extent, that the results of these methods may be very distorted. It has been proven that the developed method can be used to characterize the internal structural changes in building materials and thus contribute to the understanding of the fracture processes during mechanical loading. Up to 600 degrees C the glass spheres stay spherical and the crack is propagating through the interfacial transition zone, while at higher temperatures the glass loses its shape and the newly formed pores cause also cracks within the inclusions. The relationship between compressive strength and the maximum loading temperature was confirmed.

Published
2020

44. Assessment of the post-impact damage propagation in a carbon-fibre composite under cyclic loading: Ocena napredovanja poškodbe po udarcu pri ponavljajočih se obremenitvah kompozita z ogljikovimi vlakni

Author

Doktor, Tomáš, Fíla, Tomáš, Kytýř, Daniel, Šleichrt, Jan, and Šperl, Martin

Abstract

Carbon fibre in polyphenylene sulfide composites (C/PPS) became a popular material in the aircraft industry but its fragility and low impact resistance limits its application in primary aircraft structures. This study is focused on damage propagation in the laminated composites reinforced with carbon fibres. The damage may be inflicted during the ground maintenance, by an inflight bird strike or during a flight in severe meteorological conditions (heavy storms). The initial damage was created by a drop-weight out-of-plane impact using a spherical indenter. The response of the material was analysed by monitoring the impacted zones and their propagation history. The influenced area and specimen thickness in the centres of indents were chosen as the degradation parameters. The post-impact damage propagation induced by cyclic loading was assessed using a custom-designed computer-controlled laser-profilometery device. Both the upper and lower profiles of the specimen were scanned during the interruptions of the fatigue test. Global deformation was described with an analytically determined centroidal-axis curve. Local topography changes were obtained with a subtraction of this curve. Surface-deformation maps were created and used for a demonstration of the damage propagation in the specimen. Ogljikova vlakna v kompozitih iz polifenilen sulfida (C/PPS) so postala priljubljen material v letalski industriji, toda njihova krhkost in slaba odpornost proti udarcem omejujeta njihovo uporabo v primarnih letalskih konstrukcijah. Ta raziskava se osredinja na napredovanje poškodbe na laminiranih kompozitih, ojačanih z ogljikovimi vlakni. Poškodba lahko nastane med vzdrževanjem na tleh, pri trčenju s ptico med letom ali med letom v hudih vremenskih razmerah (huda nevihta). Začetna poškodba je bila narejena z udarno pregibnim preizkusom s kroglastim vtiskovalcem. Odziv materiala je bil analiziran z opazovanjem območij udarca in potekom napredovanja. Prizadeto območje in debelina vzorca v področju vtiska sta bila izbrana kot parametra degradacije. Napredovanje poškodbe po cikličnem obremenjevanju po udarcu je bilo ocenjeno s po meri oblikovane računalniško vodene naprave za lasersko profilometrijo. Zgornji in spodnji profil vzorca sta bila skenirana med prekinitvami preizkušanja utrujenosti. Celotna deformacija je bila opisana z analitično določeno krivuljo težiščnice. Lokalne spremembe topografije so bile dobljene z odštetjem te krivulje. Ustvarjeni videzi deformacije površine so bili uporabljeni za prikaz napredovanja poškodbe na vzorcu.

Published
2014

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