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Utilization of image and signal processing techniques for assessment of built heritage condition
Koudelka_ml., Petr; Koudelková, Veronika; Doktor, Tomáš; Kumpová, Ivana; Kytýř, Daniel; Valach, Jaroslav
2018 - anglický
Historical buildings represent invaluable heritage from the past and therefore their protection is a very important task. Assessment of their condition must not cause damage accumulation thus the least possible volume removed from the structure is essential. As many historical buildings in the Czech Republic are built using sandstone that can be considered as a typical heterogeneous system, statistical signal processing is a promising approach for determination of the representative volume element (RVE) dimensions. Such calculations can be carried out on the domain of logical arrays representing binary images of the materials microstructure. This paper deals with processing of image data obtained using SEM-BSE and high resolution flatbed scanner for determination of RVE dimensions. Advanced image processing techniques are employed and results from calculation using grayscale data are presented and compared with results calculated on the basis of color input images.
Klíčová slova:
heterogeneous systems; natural stones; image processing; K-means clustering; representative volume element
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Utilization of image and signal processing techniques for assessment of built heritage condition
Historical buildings represent invaluable heritage from the past and therefore their protection is a very important task. Assessment of their condition must not cause damage accumulation thus the ...
Multi-channel control system for in-situ laboratory loading devices
Rada, Václav; Fíla, Tomáš; Zlámal, Petr; Kytýř, Daniel; Koudelka_ml., P.
2018 - anglický
In recent years, open-source applications have replaced proprietary software in many fields. Especially open-source software tools based on Linux operating system have wide range of utilization. In terms of CNC solutions, an open-source system LinuxCNC can be used. However, the LinuxCNC control software and the graphical user interface (GUI) could be developed only on top of Hardware Abstraction Layer. Nevertheless, the LinuxCNC community provided Python Interface, which allows for controlling CNC machine using Python programming language, therefore whole control software can be developed in Python. The paper focuses on a development of a multi-process control software mainly for in-house developed loading devices operated at our institute. The software tool is based on the LinuxCNC Python Interface and Qt framework, which gives the software an ability to be modular and effectively adapted for various devices.
Klíčová slova:
CNC; controlling; LinuxCNC; Python Interface; Python; parallel programming; Qt; PyQt; Qwt; PythonQwt; LabJack
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Multi-channel control system for in-situ laboratory loading devices
In recent years, open-source applications have replaced proprietary software in many fields. Especially open-source software tools based on Linux operating system have wide range of utilization. In ...
Analysis of mini-jack technique for in situ measurement of strength
Kloiber, Michal; Tippner, J.; Kunecký, Jiří; Sebera, V.; Milch, J.; Hrivnák, Jaroslav
2017 - anglický
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.
Klíčová slova:
non-destructive testing; mini-jack technique; wood; in-situ testing; compression strength
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Mechanical analysis of scarf joint fastened using cylindrical wooden dowel
Tippner, J.; Milch, J.; Kunecký, Jiří; Kloiber, Michal; Brabec, M.; Sebera, V.
2017 - anglický
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.
Klíčová slova:
all-wooden joints; scarf joint; dowel; spruce; oak; digital image correlation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
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 - anglický
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.
Klíčová slova:
X-ray computed tomography; X-ray flourescence imaging; cultural heritage; data fusion
Dokument je dostupný na externích webových stránkách.
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 ...
Iron alloys outdoor corrosion and laboratory simulation - comparison
Majtás, Dušan; Mácová, Petra; Kreislová, Kateřina; Příhoda, J.
2017 - anglický
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.
Klíčová slova:
corrosion; wrought iron; accelerated ageing; corrosion simulation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Evaluation of effective properties of basalt textile reinforced ceramic matrix composites
Valentová, S.; Hrbek, Vladimír; Šejnoha, M.
2017 - anglický
The present paper is concerned with the analysis of a ceramic matrix composite, more specifically the plain weave textile fabric composite made of basalt fibers embedded into the pyrolyzed polysiloxane matrix. Attention is paid to the determination of effective elastic properties of the yarn via homogenization based on the Mori-Tanaka averaging scheme and the 1st order numerical homogenization method adopting a suitable representative computational model. The latter approach is then employed to simulate the response of the yarn when loaded beyond the elastic limits. The required mechanical properties of individual material phases are directly measured using nanoindentation with in-build scanning probe microscopy. Applicability of the proposed computational methodology is supported by the analysis of a unidirectional fibrous composite, representing the yarn, subjected to a macroscopically uniform strain
Klíčová slova:
basalt fibers; textile composites; homogenization; periodic unit cell; damage
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Evaluation of effective properties of basalt textile reinforced ceramic matrix composites
The present paper is concerned with the analysis of a ceramic matrix composite, more specifically the plain weave textile fabric composite made of basalt fibers embedded into the pyrolyzed ...
Deformation behaviour of gellan gum based artificial bone structures under simulated physiological conditions
Krčmářová, N.; Šleichrt, J.; Fíla, Tomáš; Koudelka_ml., Petr; Kytýř, Daniel
2017 - anglický
The paper deals with investigation of deformation behaviour of gellan gum (GG) based\nstructures prepared for regenerative medicine purposes. Investigated material was synthesized as porous spongy-like scaffold reinforced by bioactive glass (BAG) nano-particles in different concentrations. Deformation behavior was obtained employing custom designed experimental setup. This device equipped with bioreactor chamber allows to test the delivered samples under simulated physiological conditions with controlled flow and temperature. Cylindrical samples were subjected to uniaxial quasi-static loading in tension and compression. Material properties of plain scaffold buffered by 50 wt% and 70 wt% BAG were derived from a set of tensile and compression tests. The results are represented in form of stress-strain curves calculated from the acquired force and displacement data.
Klíčová slova:
gellan gum scaffold; reinforcement; uni-axial loading; simulated physiological conditions
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Deformation behaviour of gellan gum based artificial bone structures under simulated physiological conditions
The paper deals with investigation of deformation behaviour of gellan gum (GG) based\nstructures prepared for regenerative medicine purposes. Investigated material was synthesized as porous ...
Non-holonomic planar and spatial model of a ball-type tuned mass damping device
Náprstek, Jiří; Fischer, Cyril
2017 - anglický
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.
Klíčová slova:
tuned mass damper; moving ball; Appell-Gibbs formulation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
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 - anglický
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.
Klíčová slova:
foam; micro-computed tomography; Talbot-Lau grating interferometer XCT; dark-field imaging
Dokument je dostupný na externích webových stránkách.
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 ...
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