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Monitoring degradation in alkaline-activated slag materials
Get PDFThis paper deals with determining degradation changes in alkaline-activated slag-based building materials. It describes methods for determining dynamic elastic moduli obtained by acoustic non-destructive methods, including the ultrasonic pulse method and the resonance method. A finegrained mortar was chosen as the initial mix for the implementation of the experiment, the binder part of which was sodium hydroxide-activated blast-furnace granulated slag. Beams with dimensions of 40 × 40 × 160 mm were chosen as test bodies, for which acoustic non-destructive methods monitored changes in the material structure during degradation processes
RESEARCH ON THE DEVELOPMENT OF LOW-TEMPERATURE-RESISTANT FAST-CURING STRUCTURAL ADHESIVE AND STEEL PLATE STRENGTHENING CONCRETE BEAM FLEXURAL TEST
Get PDFSteel plate strengthening method is a common, efficient, and mature reinforcement method that utilizes structural adhesive to bond steel plates with concrete components to work together. It takes advantage of the excellent tensile strength of steel plates to improve the mechanical properties of the original structure. However, epoxy-based structural adhesives are highly sensitive to the environment, and curing effect at low temperatures is a key issue. This study developed a low-temperature-resistant fast-curing structural adhesive (LTR-FCA) that can achieve rapid curing at low temperatures of -5 °C. The flexural performance of reinforced concrete beams strengthened with steel plates using LTR-FCA was compared with that using Normal Structural Adhesive (NSA). Experimental results indicated that LTR-FCA could rapidly cure at a low temperature of -5°C. Compared to NSA, which cures at room temperature, the use of LTR-FCA effectively delayed the debonding of the steel plates
GEOMONITORING OF THE OPEN-PIT MINE SLOPES DURING SUBSOIL DEVELOPMENT
Get PDFThe concept of geomonitoring and its role in developing the mining industry as a case study of the development of copper and zinc deposits in central Kazakhstan ("East Saryoba" mine) has been considered. As a crucial element of the geomonitoring concept, the control of the open-pit mine\u27s slope stability has been examined. Geomonitoring is being treated as a combination of geodetic monitoring data and geomechanical properties of the surrounding rocks to analyze the possible slopes\u27 collapses. The refined approach of geomonitoring has been developed to provide appropriate reliability and accuracy. The technology is based on complex knowledge about the geological structure of the object of monitoring and applying state-of-the-art geodetic methods. Research on the geomechanical properties of the open-pit mine has been carried out. The results of these studies have been used to determine the collapse zones of the slopes of the open-pit mine. The limit values for the slopes\u27 collapse zone and inclination angle for the prospective excavation regions in the open-pit mine have been calculated using the equilibrium state equation. Those values, namely, the size of the collapse zone and the slope\u27s inclination angle, were used for the geodetic target setup. As a case study, the displacements of these targets were measured using robotic total stations placed on the control points over the geodetic network. For the installation of both geodetic equipment during the geomonitoring design and accomplishment, the authors developed the permanent measuring station construction, which provides fast and accurate centering. The first results showed that the problem of the geomonitoring design could be solved based on geomechanical rock properties accounting and their combination with the results of geodetic measurements
ANALYSIS OF MICROVASCULAR PATTERN ON HISTOLOGICAL SAMPLE OF MYOCARDIUM USING VORONOI SEGMENTATION
Get PDFRemodeling of a microvascular network is common part of pathological changes associated with wide spectrum of diseases. Quantitative analysis of these alterations relies often on analysis of a point-pattern on the histological slide, i.e. on sections through the microvascular network only. Common techniques are based on the estimation of the average density of points representing section through microvessels on the histological image. This approach inherently omits the information about the regularity of the pattern. Thus, we used approach based on the Voronoi segmentation and chose the best statistical model of areas of Voronoi cells surrounding microvessels on 20 samples of human myocardium. The best model is based on the log-normal distribution. Parameters of the model for given data can be estimated as a mean and a standard deviation of logarithms of areas of Voronoi cells. Moreover, these parameters can be transformed to the widely used measure called the microvascular density
Study of high-frequency electrodeless mercury capillary discharge in the magnetic field
Get PDFWe analyzed shapes of Hg 253.7 nm spectral line, emitted from a micro–size electrodeless Hg/Xe capillary lamp in a magnetic field for its usage in Zeeman atomic absorption spectrometry. Measurements for several different lamp positions were conducted. Obtained profiles were presented as a Fredholm integral equation of the first kind and separated from an instrumental function. The gas temperature, the dependence of Zeeman splitting on the intensity of the magnetic field, and the magnetic field’s exact value in the experiment were determined
Design strategy for the prototyping of 3D-printed continuous fiber-reinforced components for solar-powered vehicle
Get PDFContinuous fiber fused filament fabrication is an advanced 3D printing method that allows designers to produce high-performing lightweight structures, leading toward innovative design philosophies and sustainable production chains. In this work, we proposed a design strategy to manufacture selected components for a solar-powered vehicle, which consists of three stages. Firstly, the prototypes’ CAD models are developed, considering their geometric and manufacturing requirements. Then, a finite element analysis is carried out to ensure optimal fiber reinforcement of prototypes’ critical regions. Lastly, the manufacturing stage involves the slicing process and optimization of the time and cost of the printed part employing Markforged® technology. Adopting the proposed methodology, the experimental campaign investigated the print quality and performance of several prototypes of each component by adjusting printing parameters
Complex system testing based on API
Get PDFThe article describes the practical experience of testing a specific ticketing system for public transport based on blockchain technology. The testing aimed to verify the overall functionality of the complex system as well as the correct execution of the functions of its selected parts, which consist of several separately developed but closely cooperating subsystems: blockchain, clearing, and mobile application subsystem with support of bank payment system.Communication between the different parts was implemented through APIs developed for this purpose. The availability of API documentation and the implementation on Linux OS allowed the use of sophisticated tools for testing and performing both manual and automated tests. Performed tests made it possible to detect errors in the program code of the respective components and to provide the basis for their elimination. Applied approaches and tools can be used to test similar complex information-handling systems
About the choice of Tungsten carbide indenter to determine mechanical properties of superalloys by using high-temperature microhardness tester
Get PDFIn the aeronautical field, materials are used in severe environmental conditions (temperature, atmosphere), particularly in engine applications. In order to qualify mechanical properties of new composition Ni-based superalloys, ONERA performs Vickers hardness tests from room temperature up to 750 °C close to operating conditions. This method consists in applying a pyramidal tip onto the specimen to characterize hardness and mechanical resistance of the material. This simple method appears to be faster than other methods using classical hot tensile or bending tests.Nevertheless, the choice of the indenter tip for high-temperature experiments is crucial. Tungsten carbide tip is used for characterizing Ni-based superalloys. Electron microscopy and X-ray analysis are presented and discussed on new and used tungsten carbide tips. A simple experimental method to control the evolution of the indenter before and after using it in the high-temperature hardness test is explained.Evolution of hardness and mechanical resistance versus temperature by using Tabor relationship on a Nickel-based superalloy sample is compared to evolution of mechanical resistance values determined by classical high temperature tensile tests. A good agreement is found between these two methods with WC indenter. These hardness measurements could be carried out up to 1 000 °C if indenter is still available to characterize layers, coatings, composite materials, additive manufacturing materials or gradient properties materials
Hygrothermal analysis of internal insulation systems of brick historical walls using numerical simulation
No full textA numerical calculation is used for hygrothermal assessment of different wall assemblies. Interior thermal insulation systems using lime-pozzolana, calcium silicate, vacuum insulation panels and mineral wool which are applied on a common historical brick wall structure are analyzed. A comparison between vapor-open and vapor-tight systems is conducted. Moisture and temperature fields in the insulated wall and in the wooden beam-heads that are embedded in the insulated walls are carried out using WUFI and 3D Cube. The best alternative found is vapor-open system on the basis of lime-pozzolana
Finite element simulation of the UHPC reinforced negative moment zone of continuous concrete box girder after simple support (CCBGSS)
No full textIn order to explore the improvement effect of UHPC on the mechanical property and crack resistance in the negative moment zone of the continuous concrete box girder after simple support (CCBGSS), based on the experimental research, the finite element software was used to simulate and analyze the parameters of the reinforced beam. The variation trend of the load-deflection curve obtained from numerical simulation and experimental measurements was basically consistent. The minimum error value of the cracking load was 2.0%, and the maximum was 8.4%. The minimum error value of the ultimate load was 2.0%, and the maximum was only 4.4%. This showed that the finite element model can well simulate the stress behavior of the test beam in the whole process. The parameter analysis showed that the cracking load and ultimate load of the box girder increased with the increase of the thickness and length of UHPC in the negative bending moment zone. When the pouring thickness of UHPC increased from 60 mm to 100 mm, the cracking load and ultimate load increased by 10.3% and 5.6% respectively. When the pouring length of UHPC increased from 1.6 m to 2.0 m, the cracking load and ultimate load increased by 18.3% and 6.5% respectively