bluuebunny/crossref_metadata_2025_split huggingface dataset:
A review of concrete durability in marine environment
Authors: Pratiwi W D , Putra F D D , Triwulan  , Tajunnisa Y , Husin N A , Wulandari K D 
Published: September 2021

Abstract
There are many concrete constructions in marine environments. Due to its salinity content, seawater is aggressive, both towards concrete and reinforcement. Concrete interacts with seawater which causes deterioration. The chemical attack occurs at least through 3 common mechanisms: sulfate-attack, carbonation, and chloride-induced corrosion of reinforcement. The chemical resistance of concrete is determined by the porosity and chemical composition of the concrete. Partly subsitution of cement with supplementary cementitious materials (SCM) known as an effective way to create the less permeable concrete. Concrete with fly ash as SCM has excellent potential to be applied to marine construction in Indonesia because the abundant availability of fly ash in Indonesia and the presence of aluminum species in fly ash provide an opportunity to increase binding capacity to chloride.
Microstructure of Al-Mg thin free-standing films
Authors: Bajtošová L , Králík R , Křivská B , Libenská H , Veselý J , Cieslar M 
Published: September 2021

Abstract
Thin Al-Mg films were prepared by a DC magnetron sputtering on glass substrates covered with photoresist and subsequently free-standing samples were released from the substrate. The surface morphology, grain size and orientations were characterized by atomic force microscopy and transmission electron microscopy equipped with automated orientation and phase mapping software. The grain growth mechanism during sputtering is consistent with sputter deposition oblique incidence theory for growth. Strong preferred (110) orientation in direction perpendicular to the sample surface has been observed in all studied samples.
Effect of heat treatment on mechanical properties of duplex steel SAF 2507 manufactured by DED
Authors: Brázda M , Salvetr P , Rzepa S , Melzer D , Vavřík J 
Published: September 2021

Abstract
This work is focused on the influence of heat treatment on the mechanical properties of duplex steel SAF 2507 produced by direct laser deposition (DLD). Duplex steels combine the advantages of ferritic and austenitic steels and reach excellent combination of mechanical and corrosion properties. The best properties are achieved by approximately equal phase ration of ferrite and austenite. Therefore, the proportion of austenite and ferrite before and after heat treatment was investigated within the study. Direct laser deposition technology was used for sample production. The DLD works on the principle of laser melting of the feedstock material (powder), which is carried by a protective gas into the nozzle. The material is successively deposited on the build platform. This technology can be used as an additive manufacturing process for surface repairs and component modifications. In this experimental study, the samples were deposited and subsequently subjected to the heat treatment. Solution annealing was chosen as the heat treatment method. The microstructure was characterized by LM, SEM and EBSD analyses. The mechanical tests were performed by a tensile testing on miniaturized specimens extracted from the experimental material in three orientations. The heat treatment had a fundamental effect on the proportion of austenite and ferrite, but also on the resulting mechanical properties. From the mechanical properties the maximum values of YS/UTS ∼ 680/830 MPa were reached and after heat treatment ∼ 540/760 MPa were reached.
Boronizing in Arms Industry
Authors: Hajek J. , Coufal V. 
Published: September 2021

Abstract
Comparison is made between several thermochemical treatment methods, with focus on boronizing. Boronizing has the potential to become a substitute for chromium plating or nitriding (gas nitriding) in the arms industry. This experimental study explored the chemical composition, hardness, corrosion resistance, tribological properties and toughness of several surface layers and coatings. The experimental substrates were EN 32CrMoV12-10 and EN 31CrMoV9 steels. Boronizing is intended for the gas tube and piston of a specific firearm. In the boride layer, the hardness of 1900 HV0.1 was reached. In the chromium and nitrided layers, hardness was 1100 HV0.1. In these experiments, original rifle tubes and disc samples were used. The thicknesses were as follows: the chromium layer: up to 70 μam, boride layer: 100 μam and nitride layer: 290 μam. Wear properties were compared using the Pin-on-Disc wear test. Fracture toughness according to Palmquist was the highest in the nitride case and the lowest in the chromium layer. Across all the layers, the range was from 2.5 to 9.5 MN/m3/2. Some differences were found between the boride layer with post-process heat treatment and layers without heat treatment. As a result of the research, it was found that Boronizing of the gas tube proved a suitable substitute for hard chrome plating or nitriding.
Thermal conductivity of SLM deposited H13 steel
Authors: Halmešová K , Džugan J , Ackermann M , Koukolíková M , Trojanová Z 
Published: September 2021

Abstract
Hot-worked H13 tool steel was deposited using selective laser melting (SLM) process in different deposition conditions. The samples were deposited in 2 different directions: parallel and perpendicular to the base plate of SLM device. Thermal conductivity of the deposited samples was calculated on the base of laser flash measurements up to 700°C. Furthermore, the thermal expansion, specific heat, and thermal diffusivity of the deposited samples and their variations with different deposition conditions are also presented. To explain the measured differences in thermal properties, some metallographic studies together with porosity investigation are also provided. It was shown that all measured thermal properties of the samples are affected by temperature and that the microstructural defects play an important role for the resulting thermo-physical properties.
Development of a methodology for measuring fracture toughness using sub size test specimens
Authors: Chvostová E. , Džugan J , Rund M. 
Published: September 2021

Abstract
To obtain real data of mechanical properties-fracture toughness-to describe the behaviour of cracks in the material, standard 1T-CT test specimens are usually used that, according to the standard, have the dimensions of 50x62.5 and a thickness of 25 mm. In the case of lack of material obtained for example by 3D printing, SPD methods, or by semi-destructive sampling from a real component to evaluate its residual life, these tests cannot be performed using a standard sample, but can be performed using a designed miniaturized test specimen marked as 0.16T-CT with dimensions 10x10 and thickness 4 mm. This paper contains the development of a methodology for testing fracture toughness using a sub-sized test specimens and a comparison of the obtained results with the results of tests obtained using a standard specimen. The techniques based on miniaturized test specimens for determining fracture toughness have been shown here as a tool to provide a deeper insight into the fracture behaviour of a material and to understand better the behaviour of the material in cases where a limited number of experiments are available.
Advanced techniques applied to analyse the influence of the heat treatment on the mechanical properties, microstructure and texture of additively produced components from maraging steel
Authors: Koukolíková M , Brunát V , Wolf G , Simson T , Koch J 
Published: September 2021

Abstract
The experimental program Metallic materials in the process chain of additive manufacturing is focused on the characterization of laser powder bed fused materials (L-PBF). Metallographic analysis, electron backscatter diffraction supported by micro tensile testing were used to analyse the material properties of the maraging steel MS1. The main goal of the research was to use advanced techniques to investigate the influence of the additive manufacturing with very fine powders, and subsequent heat treatment on the microstructure, texture and mechanical properties of the components from maraging steel.
The influence of Zener drag on recrystallization behaviour of twin-roll cast AA8079 alloy after homogenization
Authors: Králík R , Křivská B , Bajtošová L , Cieslar M 
Published: September 2021

Abstract
Intermediate annealing is a crucial step of aluminum foil production. The as-cast material hardens during rolling and an annealing step is required at intermediate gauges to soften the material and restore its ductility. Generally, fine recrystallized structure could assure sufficient ductility for further rolling and processing. Recrystallization of the material during intermediate annealing can be controlled by a microstructure tailored during homogenization. Recrystallization behaviour of a twin-roll cast aluminum alloy AA8079 was studied. The as-cast strip was homogenized at 420 °C and 580 °C and rolled down to two different thicknesses. Evolution of microstructure of rolled materials during a model intermediate annealing was studied, and Zener drag and particle stimulated nucleation were determined as mechanisms controlling recrystallization.
Resistivity and Formation of Intermetallic Layer in Aluminum-Steel Clad Strip
Authors: Křivská B , Šlapáková M , Králík R , Bajtošová L , Cieslar M , Grydin O , Stolbchenko M , Schaper M 
Published: September 2021

Abstract
Cladding of two dissimilar materials such as aluminum and austenitic steel can bring outstanding material characteristics beyond the ones of each conventional monomaterials. The study focused on development of an Al-Fe-rich intermetallic phase formed on the aluminum/steel interface during heat treatment. Electrical resistivity measurements were performed to monitor diffusion processes and phase transformations during isochronal and isothermal annealing. Resistivity measurement results were supplemented by microscopic methods revealing the interfacial microstructure.
Study of the deformation process in an equal-channel step matrix of a new design based on computer simulation
Authors: Naizabekov A , Panin E , Lezhnev S , Volokitina I 
Published: September 2021

Abstract
The paper presents the results of computer simulation of the deformation process in equal-channel step matrix, the distinctive feature of which is the location of intermediate channel at two angles to the input and output channels. Models with values of the inclination angle in the longitudinal direction (angle α) of 135 degrees and inclination angles in the transverse direction (angle β) of 15, 25 and 35 degrees are considered. To study the stress-strain state, the following parameters were considered: equivalent strain (total strain intensity); equivalent stress (stress intensity), and the resulting deformation force. It was found that with an increase in the value of the angle β, all the characteristics of the stress-strain state increase in their absolute value. When the angle β increases from 0 to 35 degrees, the equivalent strain increases by an average of 22÷25%. The analysis of the forces showed that when the value of the angle β increases, the deformation force increases at both stages, the nature of the increase is non-monotonic. The increase in force occurs sequentially by 10, 12 and 23 kN, which indicates the exponential nature of increase in force depending on the value of the angle β. The maximum force value of 257 kN that occurs when using a matrix with angle of β=35° exceeds the standard value for β=0° by only 22%. Therefore, the best option for performing equal-channel step pressing with the flow of metal in 3 planes can be considered a matrix with angle α=135° and angle β=35°.
Tensile properties evaluation of additively manufactured AISI 316L thin wall and bulk material using various miniaturized specimen geometries
Authors: Rzepa S , Melzer D , Koukolíková M , Konopík P , Brázda M , Vavřík J 
Published: September 2021

Abstract
Additive Manufacturing is an innovative technology, which allows creating structures of complex and unique geometries layer by layer. The mechanical properties of deposited objects can vary depending on their length, thickness and deposition orientation due to different cooling rates and various thermal conductivity. Austenitic steel AISI 316L, deposited using direct energy deposition technology, was an experimental material. The technology employs a high-power laser beam as an energy source for the powder melting. During the process, a powder is blown through the nozzle by protective gas into the processing area and subsequently molten. The aim of the study was to compare basic mechanical properties of the specimens extracted from a thin wall and a bulk material. The specimens were tested in horizontal and vertical orientations in relation to the build orientation in machined and as-deposited states. The tensile characteristics of proportional and non-proportional specimens were investigated within the study. The miniaturized tensile test specimens were employed in order to examine the strength and elongation of the experimental material. The mechanical testing results were complemented by microstructural analysis using a light microscopy (LM). Based on the obtained results, it can be concluded that the specimen proportionality affects not only the specimen elongation, but also the strength values of investigated material.
Comparison of the optical and electrical energy band gap of a thin layer of polyelectrolyte based on MEH-PPV and KI
Authors: Szindler M M , Szindler M 
Published: September 2021

Abstract
A thin layer of polyelectrolyte based on Poly[2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) and potassium iodide (KI) was prepared using the sol-gel method. Comprehensive studies of the optical and electrical energy gap of the produced material were carried out. Using the Thermo Scientific Evolution 220 spectrophotometer equipped with a xenon lamp in the wavelength range from 190 to 1110nm, the absorbance A was measured. The optical energy gap (Egopt) was calculated. With the change in the concentration of potassium iodide, the change in the energy band gap of polyelectrolyte thin film was registered. In this paper, the cyclic voltammetry (CV) for testing electrochemical properties was used. The location of energy levels HOMO, LUMO and the value of the energy band gap were calculated, which is very important for polymeric materials that conduct electricity and the possibility of their use in solar cells.
Bi-Directional System Coupling for Conjugate Heat Transfer and Variable Leakage Gap CFD Analysis of Twin-Screw Compressors
Authors: Rane S , Kovačević A , Stošić N , Smith I K 
Published: September 2021

Abstract
Oil-free twin-screw compressors are essential in various industrial applications where clean compressed gas is required. Due to the absence of the cooling oil in these machines, thermal deformations are large. Hence, design clearances are generally set at a relatively large value of more than 150 μm. Leakage through these clearances are the primary source of flow loss. It is essential to predict the change of the gap size in operation accurately so that the design clearances can be minimised, allowing reliable operation and maximising compressor efficiency. To achieve this, CFD and Structural solvers were combined. The CFD model uses a single domain deforming grid of the twin-screw rotors generated in SCORG grid generator, together with ANSYS CFX flow solver. The thermal model of the rotors and housing uses ANSYS Structural solver. Two modelling systems were coupled bi-directionally to obtain variation in the radial leakage gap size for calculation of performance in the CFD model. The predicted compressor performance thus obtained was compared with measurements of flow, internal pressure-rise, power, specific power, volumetric and adiabatic efficiency. For the test case, three variations of radial gap size were evaluated, two of them with the uniform gap size of 10 μm and 160 μm and the third one with a variable gap size as predicted by the bi-directionally coupled model. The coupled model predicted this gap size to vary from 24 to 117 μm, thus predicting an improved flow and volumetric efficiency by 8.2%, lower indicated power by 2.5% and a higher adiabatic efficiency by 5.5%, in comparison to the design gap size of 160 μm. These predicted gap sizes could be used to improve the design clearances of the compressor by reducing them from 160 to 120 μm which would result in a better performance during operation.
Implementing the principles of operating processes schematization and of performance loss distribution when designing long-stroke reciprocating compressor stages
Authors: Yusha Vladimir L. , Busarov Sergey S. , Filkin Nikolay Yu. , Fedorova Maria A. , Denisenko Vladimir V. , Goncharenko Alexander A. , Shipov Vyacheslav B. , Bessonov Oleg G. 
Published: September 2021

Abstract
To compress gases up to 10.0 MPa and higher, diaphragm and multistage reciprocating compressor units are used. They are heavy, massive and complicated. The results of analyzing laboratory examples of slow-speed long-stroke stages of reciprocating compressors while gas pressurizing up to such pressure have shown the possibility of solving the problems mentioned. Such stages differ from others, that is why we cannot use common design methods in this case. The performance design method for slow-speed long-stroke compressor stages with a discharge pressure of up to 10.0 MPa is based on the well-known principles of schematization of operating processes and distribution of performance losses. With regard to the experimental studies results (indicator and temperature diagrams, integral characteristics) we have found: the volumetric efficiency, which characterizes the ratio between real and theoretical compressor performance, its main components: the volume coefficient, the pressure coefficient, the temperature coefficient, and the leakage coefficient. Dependences are obtained for calculating these coefficients, which differ significantly from the known dependences for calculating high-speed compressor stages. The analysis of the influence of various factors on the performance losses of low-capacity long-stroke compressor stages of medium and high pressure revealed that the gaps in the working chamber have the maximum impact on the performance losses, the leakage coefficient significantly depending on the discharge pressure change. The volume coefficient has much less impact due to the increased stroke-to-diameter ratio of the piston, which provides a small amount of relative dead volume. The developed method can be used for preliminary calculation of compressor stages of the considered type.
Numerical simulation and optimization of centrifugal compressor return channels: methods and results
Authors: Galerkin Y.B. , Marenina L.N. , Drozdov A.A. , Solovyeva O.A. , Soldatova K.V. 
Published: September 2021

Abstract
The authors actively use their engineering Universal Modelling Method for gas-dynamic design of centrifugal compressors for industrial partners. Currently, there are two approaches to improving the Method: improving the preliminary design and increasing the accuracy of gas-dynamic characteristics calculation. Computational Fluid Dynamics (CFD) methods give good results for the flow path stator part. Recently, massive CFD calculations of the vaneless diffusers (VLD) characteristics were generalized by a system of algebraic equations, which replaced the previous more complex mathematical model in the Method. Then, based on CFD optimization of a large series of return channels (RCh), corrections were made to the preliminary design of this element of the flow path.
This paper presents the results of the joint CFD optimization of a vaneless diffuser and a return channel. Stator elements have many geometric parameters. For a stage with the flow rate coefficient of 0.0597 and the loading factor of 0.60, only the VLD relative radial length D
4/D
2, the number and the inlet angle of the return channel vanes were optimized. Engineering calculations and design experience predicted an optimal value of D
4/D2 within the interval 1.9 - 2.0. CFD optimization demonstrated almost linear reduction of the total head loss towards the end of the investigated range D
4/D2 = 2.3. After careful optimization of the U-bend, the optimization of D
4/D2 was repeated. The influence of on the loss coefficient has decreased, but the value of D
4/D
2 = 2.3 is still far from optimum. It significantly exceeds technically acceptable radial size. The result obtained influenced the design plan of future calculation experiments with a large series of stator elements of the stages in a practically significant range of design parameters.
Optimal Designed Experiments for Reliable Model Calibration of a fixed-speed Scroll Compressor with R410A and R32
Authors: Vering Christian , Stopp Daniel , Klebig Tim , Venzik Valerius , Müller Dirk 
Published: September 2021

Abstract
Mainly to provide heat, the building sector accounts for about 18 % of overall global CO2 emissions. By exchanging conventional technologies in the near future, heat pumps are a key technology to systematically decarbonise the heat supply chain. The efficiency of a heat pump strongly depends on its compressor’s efficiency. Thus, the compressor is the subject of current research. The compressor performance depends on the fluid with its inlet and outlet conditions, an appropriate oil, and the mechanic compression principle. Based on that, the performance is expressed by the isentropic and volumetric efficiency. To describe a compressor in detail and fluid independent is challenging. Therefore, many theoretical studies have been conducted, while in comparison experimental studies are rare. To overcome this imbalance, this study focuses a detailed experimental investigation of a 4 kW Copeland scroll compressor with R410A and R32 on a fully automated compressor test stand. Within this paper, we present a method for in-depth uncertainty analysis, which ensures the usability and comparability of our experimental results to other experiments. We store our results in optimal calibrated simulation models based on optimal experimental design. This allows us to reduce experimental effort up to 70 % compared to full factorial experimental designs. To prove the method in a compressor and two fluids, we apply it to a fixed-speed scroll compressor with R410A and R32. The test stand is able to conduct all experiments automatically and part load behaviour of both refrigerants can be summarized in a model according to recent Literature with an overall uncertainty below 8 % for R410A. For R32, the method fails. Utilizing this method, we aim at open-source experiments in order to accelerate the solution of complex research questions.