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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.
2017 - English
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.
Keywords:
foam; micro-computed tomography; Talbot-Lau grating interferometer XCT; dark-field imaging
Fulltext is available at external website.
Three-dimensional characterization of polymer foams using X-ray dark-field imaging
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 ...
Analytical approach of slender structure vibration due to random component of the wind velocity
Náprstek, Jiří; Hračov, Stanislav
2017 - English
Along wind random vibration of slender structures represents one of the most important aeroelastic effects resulting from wind - structure interaction. The theoretical model being based on one-dimensional elements with continuously distributed mass and stiffness has been introduced in this paper. The system has been considered to be linear self-adjoint with strongly non-proportional linear damping due to both material of the structure and presence of vibration dampers. The additive random excitation continuously distributed in time and space is Gaussian, therefore the response is Gaussian as well. Consequently, mathematical mean value and correlation function are satisfactory for the full description of the generalized solution of the respective PDE in the stochastic meaning. The general results have been obtained mostly in the form of analytical formulae for important cases of input spectral densities. A numerical example dealing with real structure is presented.
Keywords:
random vibrations; slender structures; wind load; non-proportional damping; distributed-parameter systems
Fulltext is available at external website.
Analytical approach of slender structure vibration due to random component of the wind velocity
Along wind random vibration of slender structures represents one of the most important aeroelastic effects resulting from wind - structure interaction. The theoretical model being based on ...
Optimization of acquisition parameters in radiography and tomography
Vopálenský, Michal; Vavřík, Daniel; Kumpová, Ivana
2017 - English
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.
Keywords:
X-ray computed tomography; X-ray radiography; X-ray optimization; image processing; contrast
Fulltext is available at external website.
Optimization of acquisition parameters in radiography and tomography
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 ...
Repair of the parapet walk with battlements made from sandstone ashlar masonry with the regard to its visual authenticity and historic values – implemented sample procedure
Bláha, Jiří; Kovářová, K.; Buzek, Jaroslav; Panáček, M.; Cihla, M.; Rafl, T.; Hejný, L.; Rybařík, V.; Chamra, S.; Schröfel, J.
2016 - Czech
The multidisciplinary criteria for selecting, preparation and processing of a replacement stone for ashlar masonry were implemented in restoration and conservation of the Castle of Kost battlements – one of the most authentically survived medieval fortification monuments in the Czech Republic. Detailed description of undertaken surveys, preparation and interventions carried out within the repair process. Interdisciplinární kritéria pro výběr, přípravu a opracování náhradního kamene určeného pro opravy lícového zdiva byla použita při restaurování hradebního ochozu s cimbuřím na hradě Kosti, který patří k našim nejlépe zachovaným památkám středověkého fortifikačního stavitelství. Součástí je podrobný popis provedených průzkumů a analýz, přípravných prací a vlastního provedení opravy.
Keywords:
conservation and restoration; sandstone; ashlar masonry; stone dressing; castle battlements
Available in a digital repository NRGL
Repair of the parapet walk with battlements made from sandstone ashlar masonry with the regard to its visual authenticity and historic values – implemented sample procedure
The multidisciplinary criteria for selecting, preparation and processing of a replacement stone for ashlar masonry were implemented in restoration and conservation of the Castle of Kost battlements – ...
Methodology for determining the relevant material characteristics of historical building materials for the restoration intervention
Slížková, Zuzana; Frankeová, Dita; Tišlová, R.
2016 - Czech
The aim of this metolodogy is to present a recommended list of material properties which have to be identified and evaluated within material survey of historical momuments.\n\n Cílem této metodiky je předložit doporučený seznam materiálových vlastností, které mají být zjištěny a hodnoceny v rámci materiálového průzkumu památkových objektů.
Keywords:
survey; restoration; conservation; material characteristics; cleaning; consolidation; repairing; hydrophobization
Available in a digital repository NRGL
Methodology for determining the relevant material characteristics of historical building materials for the restoration intervention
The aim of this metolodogy is to present a recommended list of material properties which have to be identified and evaluated within material survey of historical momuments.\n\n
The methodology for determining limits and intervals of important material characteristics, repair materials and technologies for compatible intervention
Tišlová, R.; Slížková, Zuzana; Novotná, Adéla; Frankeová, Dita; Kuneš, Petr; Ďoubal, J.
2016 - Czech
The aim of this metolodogy is to create summary of important material characteristics, define limits and intervals of selected material characterisctics and its verification.\n Cílem metodiky je vytvořit přehled významných materiálových charakteristik, stanovit meze a intervaly vybraných materiálových charakteristik a jejich ověření.
Keywords:
material characteristics; repair materials; evaluation of the effect of the consolidation agent; restoration
Available in a digital repository NRGL
The methodology for determining limits and intervals of important material characteristics, repair materials and technologies for compatible intervention
The aim of this metolodogy is to create summary of important material characteristics, define limits and intervals of selected material characterisctics and its verification.\n
The methodology for the selection of appropriate restoration work
Machačko, Luboš; Gláser, Petr; Bartoš, L.; Bayer, K.; Ďoubal, J.; Justa, P.; Vojtěchovský, J.; Krhánková, K.; Vácha, Z.; Wichterlová, Z.
2016 - Czech
The aim of this methodology is to present a recommended procedure which leads to selection of optimal restoration intervention. Selection of the appropriate procedure and method of restoration and reconstruction is the primary prerequisite for the quality and efficiency of future work. Cílem této metodiky je předložit doporučený postup, na základě kterého lze provést optimální restaurátorský zásah. Výběr vhodného postupu a způsobu restaurování a obnovy je primárním předpokladem pro kvalitu a efektivnost odvedených prací.
Keywords:
investigation; restoration; conservation; compatibility; conservation programme (task); conservation report
Available in a digital repository NRGL
The methodology for the selection of appropriate restoration work
The aim of this methodology is to present a recommended procedure which leads to selection of optimal restoration intervention. Selection of the appropriate procedure and method of restoration and ...
Survey of the facial sandstone masonry of the stone coat of historic structures with the use of non-invasive analytical techniques of ground-penetrating radar
Havlín, J.; Slavíková, M.; Gláser, Petr; Válek, Jan; Pavelka, K.; Panošová Hucková, M.
2016 - Czech
This conservation procedure includes a description of basic steps, which must be followed to use the ground-penetrating radar and to gain useful data for composition visualization of facial sandstone masonry used in historic structures. Suitable settings of the GPR device are introduced for collecting data and the way of their processing with the aid of software. The conservation procedure applies a non-invasive analytical technique of GPR when surveying stone structures and therefore it can be a useful specifying tool of particular details during the execution phase of the construction-historical survey Tento památkový postup obsahuje popis základních kroků, které je třeba dodržet pro úspěšné použití georadaru a získání užitečných dat při vizualizaci skladby lícního pískovcového zdiva historických konstrukcí. Jsou zde uvedena vhodná nastavení přístroje GPR při sběru dat a jejich způsob zpracování pomocí softwaru. Památkový postup aplikuje nedestruktivní analytickou techniku GPR při průzkumu kamenných konstrukcí a může proto být užitečným upřesněním specifických podrobností při provádění stavebně historického průzkumu.
Keywords:
ground-penetrating radar; non-invasive; masonry; sandstone; survey
Available in a digital repository NRGL
Survey of the facial sandstone masonry of the stone coat of historic structures with the use of non-invasive analytical techniques of ground-penetrating radar
This conservation procedure includes a description of basic steps, which must be followed to use the ground-penetrating radar and to gain useful data for composition visualization of facial sandstone ...
The use of carpentry joints for the repair of historical structures
Kloiber, Michal; Kunecký, Jiří; Hasníková, Hana; Sebera, V.; Tippner, J.; Fajman, P.; Růžička, P.; Stejskal, D.
2016 - Czech
The conservation process describes the way of using prosthesis lap scarf carpentry joints for reconstruction of historical timber structures. This new scarf joint makes use of the strutting effect of inclined contact faces where the forces are transmitted through wooden coupling elements - wooden dowels or keys. The process consists of several chapters describing the diagnostics of original wood and the repaired structure, the design of the joint and execution of the joint. It also includes examples of succesful reconstruction made with according to this conservation process. Památkový postup popisuje způsob využití protézovacího plátového celodřevěného spoje při rekonstrukcích historických dřevěných konstrukcí. Tento nový plátový spoj využívá rozpíravého efektu šikmých čel a síly v něm jsou přenášeny pomocí dřevěných spojovacích prostředků - dřevěných kolíků či dřevěných hmoždíků. Postup se skládá z několika kapitol popisujících diagnostiku původního materiálu a opravované konstrukce, návrh spoje a jeho provádění. Obsahuje také příklady úspěšných rekonstrukcí, které byly provedeny s jeho využitím.
Keywords:
carpentry joints; scarf joint; replacement; joint execution; diagnostics
Available in a digital repository NRGL
The use of carpentry joints for the repair of historical structures
The conservation process describes the way of using prosthesis lap scarf carpentry joints for reconstruction of historical timber structures. This new scarf joint makes use of the strutting effect of ...
Lapped scarf joints for reconstruction of historical structures
Kunecký, Jiří; Fajman, P.; Hasníková, Hana; Kuklík, P.; Kloiber, Michal; Sebera, V.; Tippner, J.
2016 - English
This paper presents a description of the repair of timber structures using a prosthesis scarf\njoint designed for the replacement of damaged parts of beams. This new scarf joint makes use\nof the strutting effect of inclined contact faces where the forces are transmitted through\nwooden coupling elements - wooden dowels or keys. The scarf can be modified in four\nvariants according to the relevant stress and is suitable for historically valuable timber\nstructures. It meets both functional and aesthetic requirements. The designer - structural\nengineer will learn in the methods the load bearing capacity or stiffness of the beam with the\ndesigned joint, its recommended dimensions and detailed geometry. The contractor will\nappreciate the description of the execution and maintenance of the joint.
Keywords:
carpentry joints; scarf joint; replacement; load bearing capacity; stiffness; joint execution
Fulltext is available at external website.
Lapped scarf joints for reconstruction of historical structures
This paper presents a description of the repair of timber structures using a prosthesis scarf\njoint designed for the replacement of damaged parts of beams. This new scarf joint makes use\nof the ...
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