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Corrosion products phase identification using micro-Raman and FTIR
Majtás, Dušan ; Mácová, Petra
Phase identification of corroded metal objects might be problematic because corrosion products are usually a complex mixture of different phases. Furthermore, some of present phases may be either semi-crystalline or amorphous. The most suitable procedure is to use X-ray diffraction (XRD), for identification of crystalline phases in bulk, in combination with micro-Raman spectroscopy to obtain information on smaller scale and given location. Micro-Raman spectroscopy identifies crystalline and semi-crystalline phases. The literature also reports of the application of Mössbauer spectroscopy to identify amorphous phases. In this work, the combined use of Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy is evaluated. The methods may be interchangeable to some point. But is it safe to assume that all phases present can be detected?
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Turistická prezentace starých krovů v prostředí historických měst
Bláha, Jiří ; Panáček, M.
Shrnutí současného stavu poznání a plošné dokumentace historických krovů v českých městech. Přehled vzdělávacích a popularizačních aktivit posledních desetiletí. Vytvoření koncepce obohacení turistických atraktivit historických měst o prohlídky historických krovů a dalších významných památek stavební historie v souvisejících půdních prostorách. Jde o vedlejší produkt dlouhodobých výzkumných aktivit zaměřených na stavební památky a péči o ně, projevy regionální kulturní diverzity a transfer historických technologických inovací v evropském prostředí. Cílem je rozšíření povědomí odborné i laické veřejnosti o tradičním stavebním tesařství, jeho mistrovských dílech, stavebním vývoji a uplatnění v městském prostředí. Zkušenosti z realizace prohlídkové trasy “Pod střechami chebských domů” zprovozněné v roce 2017.
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Creep behavior of oak pegs under tension in dry and wet conditions
Kunecký, Jiří ; Kloiber, Michal ; Hasníková, Hana ; Hrivnák, Jaroslav ; Sebera, V. ; Tippner, J. ; Milch, J.
Carpentry joints equipped with oak pegs are well suited for applications where increased moisture is not a significant factor. However, for the use in outside conditions, e.g. in the repairs of historical timber bridges, the pegs connecting the two halves of the joint may deform and change their original shape. This happens especially during long-term loading and can be augmented significantly by environmental changes. Creep behavior can play a crucial role for some types of carpentry joints, especially when precise contacts of faces in the joint are required. The paper deals with experimental testing of creep behavior of 16 mm oak pegs under dry and wet conditions loaded by the combination of shear and bending between two planks made of spruce in the direction parallel to grain. The results show that the decrease of theoretical stiffness values over time plays a significant role in the force redistribution in the joint especially due to moisture effects (drop 50-70% of the original stiffness).
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The Cloak Bridge in Český Krumlov – measuring of mechanical properties
Kloiber, Michal ; Sebera, V. ; Hrivnák, Jaroslav ; Tippner, J. ; Kunecký, Jiří
Timber bridges are often exposed to harsh conditions of the environment. The exposure of the timber structure often leads to its deterioration. Standard test procedures to determine typical properties of wood cannot be used as there is the requirement of the minimum interference with the structure. Several non-destructive testing (NDT) methods for the determination of timber condition have been developed and are used. However, the results of NDT can be used to predict mechanical properties of timber elements only to a limited degree. Semi-destructive testing (SDT) methods are a compromise. In the paper a functional model of a device that allows for the measurement of conventional strength and modulus of deformation of timber in compression parallel to the grain is presented. The device is inserted to a bored hole and pushes the jaws apart with a small test jack loading the bore walls. This paper presents possible use of the device for surveys of timber bridges.
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Investigation of Strouhal number of ice-accreted bridge cables at moderate flow turbulence
Górski, P. ; Tatara, M. ; Pospíšil, Stanislav ; Kuznetsov, Sergeii
This paper is concerned with the investigation of the Strouhal number (St) for a stationary iced cable model of cable-supported bridges using wind tunnel tests with respect to three principal angles of wind attack. The investigations were carried out in the Climatic Wind Tunnel Laboratory of the Czech Academy of Sciences in Telč. The St values were determined at the flow turbulence intensity of the order of 12%, within the range of the Reynolds number from 2.4·10^4 to 12.9·10^4, based on the dominant vortex shedding frequencies measured in the wake of the model. The obtained experimental St values of the iced cable of a cable-supported bridge will allow to determine the critical wind velocity as well as will be helpful for prediction of the cable response due to the vortex excitation phenomenon at moderate flow turbulence condition.
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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.
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.
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