Number of found documents: 1104
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Non-holonomic planar and spatial model of a ball-type tuned mass damping device
Náprstek, Jiří; Fischer, Cyril
2017 - English
The area of tuned mass dampers is a wide field of inspiration for theoretical studies in non-linear dynamics and dynamic stability. The studies attempt to estimate behaviour of diverse damping devices and their reliability. The current paper deals with the response of a heavy ball rolling inside a spherical cavity under horizontal kinematic excitation. The non-linear system consists of six degrees of freedom with three non-holonomic constraints. The contact between the ball and the cavity surface is supposed to be perfect without any sliding. The mathematical model using the Appell-Gibbs function of acceleration energy is developed and discussed. Comparison with previous planar (SDOF) model which is based on the Lagrangian procedure is given. The system has an auto-parametric character and therefore semi-trivial solutions and their dynamic stability can be analysed. The most important post-critical regimes are outlined and qualitatively evaluated in resonance domain. Numerical experiments were performed when excitation frequency is slowly swept up and down to identify different modes of response. Some applications in civil engineering as a tuned mass damper, which can be used on slender structures, are mentioned. The proposed device is compared with a conventional pendulum damper. Strengths and weaknesses of both absorbers types are discussed. Keywords: tuned mass damper; moving ball; Appell-Gibbs formulation Available at various institutes of the ASCR
Non-holonomic planar and spatial model of a ball-type tuned mass damping device

The area of tuned mass dampers is a wide field of inspiration for theoretical studies in non-linear dynamics and dynamic stability. The studies attempt to estimate behaviour of diverse damping devices ...

Náprstek, Jiří; Fischer, Cyril
Ústav teoretické a aplikované mechaniky, 2017

Keltské meče
Kumpová, Ivana
2017 - Czech
Práce byla zaměřena na vytvoření metodiky využívající rentgenové (RTG) tomografické zobrazování pro průzkumy historických artefaktů na bázi kovů. V laboratoři RTG tomografie byly touto metodou zkoumány dva objekty – byly provedeny dvě tomografie raně středověkého meče v prekonzervační fázi doplněné o testovací měření bronzového náramku ze stejného období. Průzkum byl proveden za účelem odhalení technologie výroby, výzdoby a případných poškození. The work was focused on the development of the methodology using X-ray tomographic imaging for exploration of metal-based historical artefacts. In the laboratory of X-ray tomography, two objects were examined by this method - two tomography measurements of the early medieval sword in the pre-conservative phase were taken, supplemented by imaging if the bronze bracelet of the same period. The survey was conducted to reveal the technology of production, decoration and possible damage. Keywords: X-ray tomography; medieval sword; historical artefacts Available at various institutes of the ASCR
Keltské meče

Práce byla zaměřena na vytvoření metodiky využívající rentgenové (RTG) tomografické zobrazování pro průzkumy historických artefaktů na bázi kovů. V laboratoři RTG tomografie byly touto metodou ...

Kumpová, Ivana
Ústav teoretické a aplikované mechaniky, 2017

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.
2017 - English
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. Keywords: X-ray computed tomography; X-ray flourescence imaging; cultural heritage; data fusion Fulltext is available at external website.
Analysis of Baroque sculpture based on X-ray fluorescence imaging and X-ray\ncomputed tomography data fusion

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 ...

Vavřík, Daniel; Kumpová, Ivana; Vopálenský, Michal; Lauterkranc, J.
Ústav teoretické a aplikované mechaniky, 2017

Analysis of mini-jack technique for in situ measurement of strength
Kloiber, Michal; Tippner, J.; Kunecký, Jiří; Sebera, V.; Milch, J.; Hrivnák, Jaroslav
2017 - English
The paper presents a recently developed diagnostic technique for in situ determination of modulus of deformability (MODL) and conventional strength (CSL) parallel to the grain using the mini-jack inserted in bored hole. The mini-jack compression technique simulates the standard compression test, it is compared to that to examine its prediction strength (correlation coefficients). The paper shows an influence of moisture content of wood on experimental measurements using this technique. The measurement was carried out at spruce samples at three moisture contents of 12, 18 and 24%. The results of the tests prove a very good correlation of the strength determined by the proposed technique and wood density and strength determined at universal testing machine in compression parallel to the grain. The effect of the moisture content on the measurement by the mini-jack technique was proved to be significant. Beside that, the newly-developed instrument was also studied using digital image correlation (DIC) technique to analyze induced strains around the bored hole. This was studied on halved spruce samples. The DIC revealed symmetric character of the loading and significant differences between strains induced in tangential and longitudinal directions. Keywords: non-destructive testing; mini-jack technique; wood; in-situ testing; compression strength Available at various institutes of the ASCR
Analysis of mini-jack technique for in situ measurement of strength

The paper presents a recently developed diagnostic technique for in situ determination of modulus of deformability (MODL) and conventional strength (CSL) parallel to the grain using the mini-jack ...

Kloiber, Michal; Tippner, J.; Kunecký, Jiří; Sebera, V.; Milch, J.; Hrivnák, Jaroslav
Ústav teoretické a aplikované mechaniky, 2017

Mechanical analysis of scarf joint fastened using cylindrical wooden dowel
Tippner, J.; Milch, J.; Kunecký, Jiří; Kloiber, Michal; Brabec, M.; Sebera, V.
2017 - English
Traditional all-wooden woodworking joints play an important role in the behaviour of timber structures. These joints are also widely used when historically valuable constructions are being reconstructed and the connections are usually the masterpieces that testify to the high carpentry skills and knowledges of the overall mechanical behaviour. Within historical timber structures traditional carpentry joints were used while wooden dowel fixed mutual position of elements. Main aim of this study was to contribute to knowledge base about prediction and analysis of the mechanical performance of frequently used scarf joints made from spruce wood fastened using oak dowels. The objectives were to determine the joints' slip moduli and load-carrying capacity by means of theoretical and experimental approaches, in next to assess the mechanical behaviour of dowels through experimental investigation, and finally to perform a strain analysis of dowels. For these purposes, the optical technique employing three-dimensional full-field digital image correlation was used. The experiments were done on the full-scale specimens meeting the requirements of European standards (EN 383 and EN 26891), which were made from Norway spruce (Picea abies L. Karst.) and English oak (Quercus robur L.). The mechanical load consisted in tensile parallel and perpendicular to grain direction within the main components. The results of this study showed good correlation between theoretical approach based on based on Beam on Elastic Foundation theory and European yield model theory and experimental observations. Keywords: all-wooden joints; scarf joint; dowel; spruce; oak; digital image correlation Available at various institutes of the ASCR
Mechanical analysis of scarf joint fastened using cylindrical wooden dowel

Traditional all-wooden woodworking joints play an important role in the behaviour of timber structures. These joints are also widely used when historically valuable constructions are being ...

Tippner, J.; Milch, J.; Kunecký, Jiří; Kloiber, Michal; Brabec, M.; Sebera, V.
Ústav teoretické a aplikované mechaniky, 2017

Zhodnocení jakostního stavu dřevěné konstrukce krovu, stropních konstrukcí v sondách, truhlářských prvků a zdiva Nové proboštství, nám. sv. Jiří č.p. 34, Pražský Hrad
Drdácký, Miloš; Frankl, Jiří; Kloiber, Michal
2017 - Czech
Zpráva obsahuje zhodnocení jakostního stavu dřevěné konstrukce krovu, stropních konstrukcí v sondách, truhlářských prvků a zdiva objektu Nové proboštství (Pražský hrad, nám. sv. Jiří č.p. 34) v souvislosti s plánovanou obnovou budovy. The report includes the results of the study focusing on the material properties of historical wooden roof structure and assessment of the state regarding the planned building reconstruction. Keywords: wooden roof structure; joinery elements; quality of wood Available at various institutes of the ASCR
Zhodnocení jakostního stavu dřevěné konstrukce krovu, stropních konstrukcí v sondách, truhlářských prvků a zdiva Nové proboštství, nám. sv. Jiří č.p. 34, Pražský Hrad

Zpráva obsahuje zhodnocení jakostního stavu dřevěné konstrukce krovu, stropních konstrukcí v sondách, truhlářských prvků a zdiva objektu Nové proboštství (Pražský hrad, nám. sv. Jiří č.p. 34) v ...

Drdácký, Miloš; Frankl, Jiří; Kloiber, Michal
Ústav teoretické a aplikované mechaniky, 2017

Chemical and microstructural characterization of the render, sampled from Gloriette, the US Embassy in Prague 1
Slížková, Zuzana; Frankeová, Dita; Viani, Alberto; Hauková, Petra; Koudelková, Veronika; Svoboda, Milan
2017 - English
The aim of the work was to analyze the mortar taken from the Gloriette (US Embassy, Prague 1). Analyzes were performed for the binder and filler characterization and the sample was also dissolved in HCl to determine the mixing ratio. Keywords: survey; material characterization; chemical composition; binder and aggregate characterization Available at various institutes of the ASCR
Chemical and microstructural characterization of the render, sampled from Gloriette, the US Embassy in Prague 1

The aim of the work was to analyze the mortar taken from the Gloriette (US Embassy, Prague 1). Analyzes were performed for the binder and filler characterization and the sample was also dissolved in ...

Slížková, Zuzana; Frankeová, Dita; Viani, Alberto; Hauková, Petra; Koudelková, Veronika; Svoboda, Milan
Ústav teoretické a aplikované mechaniky, 2017

Iron alloys outdoor corrosion and laboratory simulation - comparison
Majtás, Dušan; Mácová, Petra; Kreislová, Kateřina; Příhoda, J.
2017 - English
Simulation of iron alloy corrosion is widespread used to predict corrosion resistance. The simulation using corrosion chambers or climatic chambers provides reasonable information on corrosion resistance, the corrosion rate however must be compared to real exposition as the corrosion in simulated environment is accelerated compared to real situation. However the composition of corrosion products and its structure is different question. The corrosion products composition is dependent on corrosion process. The phases present are most likely the same, most voluminous hydrated oxides and oxy-hydroxides on the outside where the less voluminous oxides are present in the lower layers. However this macroscopic phase structure may not fully describe the layered structure of corrosion products, thickness of corrosion products or mechanical properties. In the vicinity of crack in corrosion products the structure is more likely to be similar to the structure near the surface. Keywords: corrosion; wrought iron; accelerated ageing; corrosion simulation Available at various institutes of the ASCR
Iron alloys outdoor corrosion and laboratory simulation - comparison

Simulation of iron alloy corrosion is widespread used to predict corrosion resistance. The simulation using corrosion chambers or climatic chambers provides reasonable information on corrosion ...

Majtás, Dušan; Mácová, Petra; Kreislová, Kateřina; Příhoda, J.
Ústav teoretické a aplikované mechaniky, 2017

Absorpční vlastnosti vybraných vápencových soch (měření nasákavosti vodou in situ pomocí mikrotrubice). Zhodnocení vlivu různých povrchových úprav na absorpci vody vápencem – orientační stanovení nasákavosti
Hasníková, Hana; Slížková, Zuzana
2017 - Czech
Zpráva obsahuje výsledky zkoušek nasákavosti povrchu vápence, které byly provedeny na několika vápencových sochách in situ pomocí mikrotrubice. Zároveň byl zkoušen efekt různých povrchových úprav (nátěrů) vápence na nasákavost povrchu vodou. Zpráva obsahuje výsledky zkoušek nasákavosti povrchu vápence, které byly provedeny na několika vápencových sochách in situ pomocí mikrotrubice. Zároveň byl zkoušen efekt různých povrchových úprav (nátěrů) vápence na nasákavost povrchu vodou. Keywords: water absorption; limestone; microtube; protective treatment; paints Available at various institutes of the ASCR
Absorpční vlastnosti vybraných vápencových soch (měření nasákavosti vodou in situ pomocí mikrotrubice). Zhodnocení vlivu různých povrchových úprav na absorpci vody vápencem – orientační stanovení nasákavosti

Zpráva obsahuje výsledky zkoušek nasákavosti povrchu vápence, které byly provedeny na několika vápencových sochách in situ pomocí mikrotrubice. Zároveň byl zkoušen efekt různých povrchových úprav ...

Hasníková, Hana; Slížková, Zuzana
Ústav teoretické a aplikované mechaniky, 2017

Materiálové průzkumy pro účel památkové obnovy objektu Nové proboštství, nám. sv. Jiří č.p. 34, Pražský Hrad
Drdácký, Miloš; Slížková, Zuzana; Frankeová, Dita; Hasníková, Hana; Hauková, Petra; Koudelková, Veronika; Kozlovcev, Petr; Ševčík, Radek; Wolf, Benjamin
2017 - Czech
Zpráva obsahuje výsledky materiálových analýz vzorků omítek a kamene, odebraných z fasád a vnitřních omítek objektu Nové proboštství (Pražský hrad, nám. sv. Jiří č.p. 34). Předmětem studia bylo chemické složení a mikrostruktura omítek, petrografie pískovce, pórovitost materiálů rtuťovou porozimetrií, povrchová nasákavost omítek, obsah a distribuce vlhkosti ve zdivu, obsah a chemické složení vodorozpustných solí v omítkách. Výsledky analýz jsou podkladem pro budoucí návrh stavební obnovy objektu a postupy restaurování uměleckých prvků. The report contains the results of the material analyses of plasters and stone samples taken from the facades and interior plasters of the historical building named “Nové Probošství” (Pražský hrad, nám. sv. Jiří č.p. 34).). The topic of the study was determination of the chemical composition and the microstructure of historical plasters and renders, sandstone petrography, porosity of materials by means of MIP, water absorption of plasters by tubes, the water content and the moisture distribution in masonry wall, the content and the chemical composition of water-soluble salts in plasters and renders. The results of the study serves as the basis for the future design of the building renovation and the restoration of the artistic elements.\n Keywords: historic plaster; historic render; chemical composition; survey; historic building; material characterization Available at various institutes of the ASCR
Materiálové průzkumy pro účel památkové obnovy objektu Nové proboštství, nám. sv. Jiří č.p. 34, Pražský Hrad

Zpráva obsahuje výsledky materiálových analýz vzorků omítek a kamene, odebraných z fasád a vnitřních omítek objektu Nové proboštství (Pražský hrad, nám. sv. Jiří č.p. 34). Předmětem studia bylo ...

Drdácký, Miloš; Slížková, Zuzana; Frankeová, Dita; Hasníková, Hana; Hauková, Petra; Koudelková, Veronika; Kozlovcev, Petr; Ševčík, Radek; Wolf, Benjamin
Ústav teoretické a aplikované mechaniky, 2017

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