bluuebunny/crossref_metadata_2025_split huggingface dataset:
Utilization of basalt fabrics as reinforcement for alkali-activated blast furnace slag systems
Authors: Hruby P , Kalina L , Masilko J , Kimm M , Gries T 
Published: August 2019

Abstract
Alkali-activated materials based on the alkali-activated blast furnace slag (AABFS) seem to be a suitable alternative construction material due to the environmental and economic aspects. More widespread application potential could be supported by the utilization of fabric reinforcement into the matrix to form AABFS composite with improved mechanical properties. The basalt fibres or fabrics (BFs) represent a reinforcing material suitable for the AABFS due to its favourable price/properties ratio. However, the question of fibres stability under the alkaline conditions should be taken into account. The effect of BFs implementation in one or more layers into various types of matrices to the mechanical properties was studied with the regard to the compressive and flexural strengths. The used matrices were based on the alkali-activation of the BFS with various activators. The fabric/matrix adhesion same as the transition zone properties were studied using the SEM analysis and pull-out tests. Indication of appreciable improvement of mechanical properties utilizing one layer of BFs for some of the mixtures activated using sodium water glass and sodium carbonate was found out.
Application of carbon black in conductive fly ash geopolymer mortars
Authors: Mizerová C , Kusák I , Rovnaník P 
Published: August 2019

Abstract
Materials with enhanced electrical properties are widely studied concerning their future application in smart or self-sensing constructions. Carbon black is known as one of the inexpensive multipurpose admixtures used in polymeric materials. This study is focused on the application of carbon black in fly ash geopolymer mortar to enhance its conductivity and other electrical properties. Geopolymer samples were prepared with the carbon black content from 0.5 to 4.0% to evaluate their performance in selected electrical properties (conductivity, resistance, capacitance). Further investigations included its influence on the mechanical properties (compressive and flexural strength) and microstructure of the binder (mercury intrusion porosimetry, SEM). Despite the considerable improvement in conductivity, the amount of conductive filler over 2% was also associated with increased porosity and reduced compressive strengths.
Stabilization of the ammonia in SNCR fly ash - the influence of tannins presence on the preparation of an autoclaved aerated concrete
Authors: Galvankova L , Ledl M , Beranova D , Opravil T 
Published: August 2019

AbstractDue to the legislative regulations on NOxemissions, a selective non-catalytic reduction (SNCR) technology had been introduced to a coal combustion process in power plants. The valuable by-product, fly ash, contains ammonia in the form of soluble salts, e.g. NH4HSO4and (NH4)2SO4. After mixing SNCR fly ash with cement, thanks to the rise of pH, the toxic ammonia releases and contaminates the working area, so the presence of these salts is undesirable in an autoclaved aerated concrete (AAC) manufacturing process. A possible solution is the conversion of soluble ammonium salts to an insoluble form. Tannins are a class of polyphenolic biomolecules, which react with the ammonium ions to form insoluble compounds. The AAC samples were mixed using SNCR fly ash and two different ammonium binding additives - pure tannic acid and the cost-effective animal food supplement containing chestnut tannins. The influence of additives on the hydration process of the starting mixture was studied by isoperibolic calorimetry. The results suggest that the cost-effective source of tannins retards the hydration. The presence of insoluble compounds was studied by the infrared spectroscopy.
Improving the dispersion of silica fume in cement pastes and mortars
Authors: Janca M , Siler P , Opravil T , Kotrla J 
Published: August 2019

Abstract
There are many possibilities how to improve concrete properties such as compressive strength, flexural strength, durability, and others. The change in the composition of ordinary Portland concrete (OPC) is one possible way. This change may result in the formation of concrete with added properties known as high-performance concrete (HPC). Traditional methods used to receive high-performance concrete design and manufacture emphasize the removal of coarse aggregates. This is achieved by using the specially sorted fine aggregates at relatively low doses along with super-plasticizers and silica fume. Problem with fine reactive aggregates is their agglomeration which causes reduction of the reactive surface. This work is focused on evaluation of the ultrasound technology for the dispersion of silica fume. For comparison, different cement mixtures were prepared to study the effects of the treatment of silica fume prior to its use in HPC applications.
Effects of shrinkage-reducing admixtures on autogenous shrinkage in alkali-activated materials
Authors: Kotrla J , Soukal F , Bilek V , Alexa M 
Published: August 2019

Abstract
This paper deals with possible solutions of chemical and autogenous shrinkage of alkali-activated blast furnace slag (AAS). Shrinkage is the main reason why AAS is not used in practice. One of the solutions how to reduce the shrinkage is the utilization of special chemical admixtures. In concrete technology, the use of chemical compounds based on hydrocarbon alcohols is well known, however the efficiency in AAS is still very poorly elucidated. Therefore, isopropanol was used in this study. The main aim of the work was to recognize and study the relations between chemical processes in the early stages of hydration. The effect of isopropanol on alkali activation was determined by calorimetric measurements and compared with the initial and final setting time of binder. It was found out that the presence of isopropanol additive had only insignificant effect on the setting time. On the other hand, the results indicated that an increasing amount of isopropanol deaccelerates the hydration process which was represented by smaller amount of primary CSH gel formation and delayed time of secondary binder phase formation.
Mechanical activation of two different types of fly ash and their effect on alkali activation.
Authors: Marcin M , Sisol M , Brezani I , Behunova D 
Published: August 2019

Abstract
The article aim is to analyze the influence of mechanical activation of a fly ash, with different proportion of mechanically activated and not mechanically activated material on alkali activation. The paper describes fly ash based geopolymers and their mechanical properties. Fly ashes were mixed in four different ratios with mechanically activated fly ash. Activation solution was constant in all specimens. Compressive and flexural strengths of the hardened product were tested after 7 and 28 days of the storage in laboratory conditions and samples were cured after activation in hot air chamber for 6 hours in 80°C temperature. The results show how mechanical activation of materials affects their strengths with highest amount achieved was 44 MPa.
Properties of the composite with recycled concrete manufactured by modified technology
Authors: Trtik T , Seps K , Chylik R , Fladr J , Pavlu T 
Published: August 2019

Abstract
The article describes basic mechanical, physical and durability characteristics of concrete with recycled aggregate. Recycled concrete aggregates from AZS s.r.o. are made using newly modified technology and properties for use in concrete have been tested. In this part of the research the compressive strength, tensile strength, modulus, freeze and thaw resistance are tested. The basic aim was to test two mixtures with fifty percent substitution of the coarse component of natural aggregate by recycled one (the standard EN 206 does not already allow this) and to prove that such a quantity of recycled aggregate can be used for concrete constructions. The properties were tested on 150 mm cubes and beams 100 x 100 x 400 mm after 28 days.
The products of a high temperature reaction of fly ash with lime and soda
Authors: Beranova D , Galvankova L , Masilko J , Ptacek P 
Published: August 2019

Abstract
A composition of coal combustion fly ash depends on a coal composition and conditions of a combustion process. The main components are SiO2 and Al2O3. An amount of Al2O3 in coal combustion fly ash is relatively high, about 30–40%, and for this reason, the fly ash could be potentially used as a raw material source for alumina production. There are several ways to get alumina. The fly ash could be acid leached or sintered with a suitable additive. One of the possible sintering processes is lime-soda sinter process. The article deals with products of lime-soda sinter process of the fly ash produced from brown coal in Czech thermal power plant. The phase composition of sintered material was determined by X-ray diffraction analysis (XRD). The presence of sodium aluminate and dicalcium silicate was confirmed.
The determination of measurement errors in impedance spectroscopy
Authors: Lunak M , Kusak I , Chobola Z 
Published: August 2019

Abstract
The paper deals with the methodology, quantification and comparison of measurement deviations for two types of the ceramic shard. The ceramic material has better polarization properties than concrete material. For impedance measurement the ceramic shard is more appropriate. The IS method diagnostics based on processing of measured data which aims evaluating the absolute error and the relative error (deviation) of the loss factor values. Results show the spectrum parts which are useful in the lower frequency range only. When Agilent 33220A and Agilent 54645A are used to carry out the IS, the most important factor from the viewpoint of the tgδ(f) determination accuracy is the accuracy of the phase shift between the excitation signal and that at the measured system output. Other factors are the measurement accuracy of the electric capacity and resistance of the oscilloscope input channel.
Examples of testing methods focussed on evaluation of corrosion influence on steel structures
Authors: Sperl M , Gajdos L 
Published: August 2019

Abstract
The paper presents methodologies and results of two case studies dealing with corrosion damage in steels. Specifically, it is concerned with corrosion fatigue and stress corrosion cracking. Description is given of preparing test specimens, special devices and loading frames that have been used to obtain significant experimental results. These are referred to influence of three different chemical solutions on the fatigue life of specimens taken from L485MB steel crude oil pipeline IKL. In the second part of the paper negative effects of stress corrosion cracking on the fracture toughness of structural steel CSN411353 were investigated and main results of this investigation are presented.
Analysis of cutting forces and surface quality during face milling of a magnesium alloy
Authors: Chirita B , Grigoras C , Tampu C , Herghelegiu E 
Published: August 2019

Abstract
This paper presents an experimental study carried out in order to assess the effects of the cutting parameters (cutting speed, feed and depth of cut) and also of cooling conditions on the cutting force and the surface quality during high speed face milling of a magnesium alloy. With its high ratio of strength to weight, good machinability and overall physico – mechanical properties magnesium has attracted a large interest upon itself, especially in fields such as automotive, aeronautics, electronics or biomaterials. On the other hand, there has been lately an increased interest for cooling techniques that are more environmentally friendly, which is why in this study two cooling systems were used: dry machining and minimum quantity lubrication (MQL). The tests have been organised according to design of experiment technique. By using the response surface methodology (RSM), a central composite experimental matrix was designed. Statistical analysis (ANOVA) has allowed to create mathematical models of the cutting force and surface roughness and to analyse the effects of the effects of the input parameters on these outcomes. It was thus revealed that the depth of cut and the feed, and the interactions feed – depth of cut and feed direction – cooling, respectively, have the most significant influence on the main cutting force, whereas when it comes to the surface roughness, the most significant factors were the feed, the feed direction and the interaction between feed direction and cooling type.
Some considerations on the welding heat flow
Authors: Cohal V 
Published: August 2019

Abstract
The modelling of a weld is not only related to the heat flow in the thermal part of the simulations. Addition of additive material and the simplification of thermal and mechanical behaviour should be considered. The basic idea is to replace a complex physical process with a much simpler one. This brings not only approximations, but also the need for calibration procedures to determine the heat flow. In the present paper we aim to model the relationship between welding temperature variation depending on the time and depth, and to model the relationship between stress and distance from the heat source (welding).
MAG welding of 960QL quenched and tempered steel
Authors: Gorka J , Kotarska A 
Published: August 2019

Abstract
The article presents research of the welding technology of S960QL quenched and tempered steel with the thickness of 10 mm. The main problem during welding heat-treated fine-grained steels is cold cracking. The aim of the research was to develop welding technology of tested steel to obtain high ductility and strength properties of the joint and to avoid the problem of crack formation after welding process. For the test the butt joint was welded. For this it was used MAG process in the flat position. Welding process was carried out based on preliminary tests and pre-prepared Welding Procedure Specification according to ISO 15609-1 standard. During welding the M21 mixture was used as the shielding gas. As the filler metal a solid wire G Mn4Ni2.5CrMo was used. The welded joint was tested in accordance with the ISO 15614 standard requirements. The research included non-destructive tests and destructive tests. The non-destructive tests included visual, magnetic particle and radiographic tests. The destructive tests included transverse tensile, root and face bend, impact, macroscopic, microscopic and hardness. Impact test was carried out in the temperature of - 20°C. Hardness measurements were made using the Vickers method and the load of 9.80 N. All of the tests ended with the positive result. The results of research show that tested welding technology and pre-heating temperature equal to 80°C allow to obtain a welded joint meeting the high quality requirements and the international standards requirements.
Scuffing analysis of roller-shoe mechanism after an aggressive test
Authors: Iordache C R , Ciornei F C , Bujoreanu C 
Published: August 2019

Abstract
The roller-shoe assembly is a known and efficient mechanism used for movement transmission in order to obtain mechanical energy. This mechanism is found in high pressure pumps and its role is to change the rotating motion in a translation one. During the running time, some wear types can be identified such as scuffing, corrosion, material removal. Scuffing is the main type of wear appearing in this mechanism. The aim of our paper is to analyse the behaviour of these two components (roller and shoe) over an aggravating test. The main defect is low clearance between components. The roller and shoe assembly is mounted in a diesel fuel pump for test. The test chosen for this experiment is Low Sommerfeld Number. It was stopped after 10% from time set. After visual analysis, it was observed the roller-shoe scuffing. The shoe was analysed and it was observed that the diamond like carbon (DLC) layer is non-conform. In the same pump, the affected components were replaced with new components to be convinced that the wear was caused by low clearance between them correlated to non-conform DLC layer. The test results confirm the reason of scuffing.
An analysis on some mechanical properties of AlMg10-SiCp ultralight metal composites
Authors: Rusu O , Rusu I 
Published: August 2019

Abstract
The paper presents some results on analysis of some mechanical properties of AlMg10-SiCp composite materials, namely hardness and behaviour at static compression. Hardness values clearly separated the range of cellular composite materials from the porous ones, the compression tests data showing that with the increase of porosity the energy absorbed by the composite materials rises, the cellular composites requiring a higher mechanical deformation work that the porous ones. The increase of the silicon carbide percentage causes the increase of mechanical deformation work and of the absorbed energy, which can be explained by the stabilizing role of the respective particles on the composite material cells walls. The investigated samples were obtained using two methods: a method based on melt bubbling with a reactive gas (M1) and a method based on using various salts powders particles, soluble in suitable solvents (M2). We chose AlMg10 alloy for the material base and silicon carbide reinforcement particles introduced in varying amounts in the base mass (5%, 10% and 15% SiC). First method leads us to cellular composites and the second one to porous composites.
Numerical study of the dynamic characteristics of a hybrid steel-concrete bridge
Authors: Scutaru M C , Taranu N , Comisu C C , Boaca G , Ungureanu D , Hudisteanu I 
Published: August 2019

Abstract
Due to the continuous development of the transportation sector and the industrial areas, the roads network has become complex nowadays. The administrators of these networks are thus responsible for maintaining it in proper conditions, using the limited budget available, insufficient for the many structures and problems identified across the network. Therefore, effective systems have been created and developed to prioritize the required works, and the benefits of their implementation have been ascertained from the early stages of the degradation development. One of these systems is the modern methodology for assessing the structural state of bridges, called Structural Health Monitoring (SHM), responsible for discovering and monitoring the degradation occurrence and development. In this paper, the authors present the numerical modelling and the dynamic analysis of a bridge with mixed steel-concrete structure. The bridge is located in Romania, ensuring the continuity of DN 28 road near Scheia. The bridge superstructure, 220.70 m in length, was fully modelled using the SAP2000 program, highlighting the specific behaviour of a continuous girder. The frequencies and deformations for the first four vibration modes were determined. The data will be used in a forthcoming experimental study and compared to those recorded in-situ, in order to determine the structural degradation.
The impact of selected CNC machining parameters on the surface roughness of the 7075 aluminium alloy
Authors: Sobek M , Grabowski L 
Published: August 2019

Abstract
Modern machining operations are characterized by very high precision and high quality of the surface. In order to achieve such surface quality, many factors influencing the tested parameters should be taken consideration. The most important parameter that allows estimating surface quality after machining is the roughness parameter, and more precisely arithmetical mean deviation of the assessed profile - Ra. The paper titled “The impact of selected CNC machining parameters on the surface roughness of the 7075 aluminum alloy” describes the test process, which aims to set parameters of machining that allow obtaining the highest quality of the surface of the processed material. During the research, a number of tests were carried out. The tests were carried out with various machining parameters. During the research cycle, two main parameters were taken into consideration that have an impact on the quality of the surface. The research process assumed a change of the speed and feed parameters. Afterward, a dependence between them and surface quality was assessed. Other parameters such as the cutting direction, the number of tool blades and the depth of cut remained unchanged. All tests were carried out on samples made of 7075 aluminum alloy (PA9, AlAnMgCu1,5). The samples were made using the MAZAK VTC-530C CNC machine. A portable surface roughness measuring device MarSurf PS10 was used for data acquisition. Further testing will also include other parameters. Such an approach will allow gathering a full set of information about proper processing of that particular material. Designed testing process will be also possible to apply to any other material.
Analytical and graphical modelling of the cutting scheme when generating with a pinion cutter
Authors: Bordeanu M , Frumusanu G , Oancea N 
Published: August 2019

Abstract
The teeth generation in the case of the cylindrical gears with involute profile is frequently realized with tools of pinion cutter type, on specialized slotting machine tools. In general, during gear teeth machining, several teeth of the tool are concomitantly in contact with the worked part, each one detaching a separate chip. The process is characterized by important unevenness of these chips cumulated area, depending on the relative position between the pinion cutter and the worked part. This transforms into cutting force and cutting torque unevenness and negatively influences both machine tool operating and tool life. The paper addresses the problem of smoothing the detached chips cumulated area at the consecutive strokes of the tool, along the rolling motion between it and the worked part, in order to obtain a main cutting torque as uniform as possible. In this purpose, the analytical modelling of the tool/worked part contact is realized at first, in the cases of generating both exterior and interior gears with involute straight teeth. Then, because the analytical solution is very laborious, a modelling algorithm is developed in one of the most performant graphical environments, which is CATIA. By implementing the graphical solution, the variation of detached chips cumulated area can be determined and the required variation law of the rolling feed, leading to process smoothing, can also be found. A numerical approached case study, concerning the teeth machining for an exterior gear is also presented.
Considerations on longitudinal dynamic effects of unbraked vehicle in passenger train composition – parametric study
Authors: Cruceanu C , Craciun C 
Published: August 2019

Abstract
The study investigates the trains’ longitudinal dynamic evolutions in certain unusual situations that may be encountered, even rarely, in railway operation. It is about the case of operating passenger trains having in componence a vehicle with isolated braking system. This is a state that, according to regulations, is generally not acceptable, but there are circumstances that can conduct to exceptions. Our purpose is to find out by numerical simulations the influence that certain parameters, such as the number of vehicles of the train, the weight of locomotive and the position of the unbraked vehicle, have on the longitudinal dynamics of passenger trains during braking actions. The numerical simulations were performed for trains in classical composition, meaning a locomotive hauling 3 up to 19 passenger vehicles, thus covering virtually all the current situations encountered in operation. In simulations there were considered all the possible placements of the unbraked vehicle within the train body. The main outcomes, submitted to a comprehensive analyse, are the maximum in-train forces and the position in long of the train of the most affected couplers by longitudinal dynamic compression (buff) and tensile (draft) forces. The time dependency of in-train forces is also discussed.