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Influence of a Directional Dependenceon Mechanical Properties of Composites Reinforced with Chopped Carbon Fibre Produced by Additive Manufacturing

Majko Jaroslav, Handrik Marian, Vaško Milan, Sága Milan, Kopas Peter, Dorčiak Filip, Sapietová Alžbeta

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 2

455--461

EN

Progress in the industry is accompanied by the development of new materials and more efficient technological production processes. At present, additive production is becoming very attractive in all industries (research, development, production), which brings a number of advantages compared to subtractive methods (customization, production speed, control of material properties by users, etc.). The main advantage of 3D printing is the controlled deposition of material in defined places. Instead of demanding manual labour, fully automated production via computers leads to the manufacturing of complex components from materials whose production in conventional ways would be problematic or even impossible. Because these are new technologies, the main direction of research at present is to identify the basic physical properties of these materials under different types of loading. The main goal of this article is to observe the dependence of the behaviour of the extruded material (thermoplastic reinforced with chopped carbon fibre) on the printing parameters (thickness of the lamina, the orientation of the fibres of the printed material, etc.). Based on published scientific works, it appears that these settings have a significant impact on the achieved physical properties. This is the reason why the authors decided to analyze the influence of these parameters on the basis of processed data from experimental measurements of mechanical properties in the MATLAB program. As this is FFF printing, an essential condition is to identify and specify the directional dependence of the behavior of the printed material. This physical phenomenon is a necessary condition for gradual knowledge for the purposes of a subsequent mathematical description of the material properties. According to the authors, for the purposes of modeling these materials in FEM-based programs, it is essential to define the directional dependence in the plane of the lamina.

2

Axial stiffness for large-scale ball slewing rings with four-point contact

Hrcek Slavomir, Kohar Robert, Steininger Jan

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

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Vol. 69, nr 2

art. no. e136725

EN

This article deals with the design of slewing rings (slewing bearings). A fully parametric, 3D virtual model of a ball slewing ring with four-point contact was created in the PTC/Creo Parametric CAD system. This model was subsequently used for finite-element analysis using Ansys/Workbench CAE software. The purpose of the FEM analysis was to determine the axial stiffness characteristics. Results of FEM analysis were experimentally verified using a test bench. At the end of the article, we present the nomograms of the deformation constant for different pitch diameters, rolling element diameters and contact angles.

3

Changes in aerodynamic parameters for 5-stage steam turbine during warming and gradual start-up to nominal operating parameters

Hoznedl M., Bednář L., Tajč L.

Transactions of the Institute of Fluid-Flow Machinery

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2016

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nr 134

45--62

EN

The results of experiments on the 5-stage steam turbine are presented. The parameters of individual stages as well as the whole turbine are observed during the gradual start-up to nominal operating parameters. The pressures and temperatures are shown at stages in idling, heating up the experimental turbine and during the transition to operating speed. A greater attention is devoted to three selected operational conditions with diﬀerent processed enthalpy drops. Problems with eﬃciency and enthalpy drops measurement during warming are described. The attempts to measure ﬂow parameters quickly and without time for heating of turbine casings and other parts are often in the experimental research caused byprice of the survey. This contributionÞs task is to inform about these situations and to avoid confused and untrue results obtained by somewhat hasty measurements due to reduction and optimisation of costs.

4

Influence of nearby structure on the wind flow around the cube structure

Olekšáková I., Hubová O., Konečná L.

Roczniki Inżynierii Budowlanej

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2015

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z. 15

29--35

EN

The influence of a nearby structure on the turbulent wind flow around the cube structure was investigated in this paper. This problem was solved by two different methods. The first one was the numerical solution by CFD simulations. Obtained results were compared with the results from tests made in the wind tunnel. Description of the problem, theory and basic equations, specification of the 3D simulations and experimental measurements were mentioned. From the evaluation of the results, pressure coefficients for this type of structure and for three solved cases, were determined. Pressure coefficients determined by the Eurocode were larger than the values determined by the tests and CFD simulations. In the case of self-standing cube, pressure coefficients were following: Cp=-2.35 (CFD), Cp=-2.404 (test). Deviations were relatively small. Hence, used k-ε model is suitable for determination of the maximum values of pressure coefficients Cp in the investigated case.

5

Data-based method for the determination of temperature dependence of heat capacity of highly dispersed powders

Karnina A., Gyrenko A., Klymenko A., Mysov O.

ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes

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2015

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Vol. 4, No 4

23--28

EN

Accuracy of engineering and economic calculations in different areas requires the use of accurate and prompt values of heat capacity for new or modified materials. A number of existing methods have an error in measuring the heat capacity of powder materials, and use non-standard devices and electric heaters which are not produced industrially. This work is aimed at developing the method for determining the heat capacity of the powder, accuracy evaluation of this method and mathematical processing of experimental data to determine the temperature dependence of the molar heat capacity. To solve the problem the method based on the DTA technique was developed. The measuring apparatus for determining the temperature dependence of the heat capacity includes two standard cups for DTA analysis with investigated material and MgO, heat-variable resistor of film type Pt100, multichannel recorder. The apparatus is placed in a drying oven. From the theory of heat transfer and the assumption about steady-flow heat transfer the equation for molar heat capacity was obtained. The method requires the measuring of temperature of the investigated material and MgO during the linear heat of the drying oven as well as air temperature in the oven. Empirical values of heat capacity of standard substances calculated by the equation for each temperature were compared with the values from reference data. The uncertainty of finding the heat capacity did not exceed 0,5%.

6

Influence of operating parameters on thermodynamic efficiency of experimental turbine with 1000 MW HP part

Hoznedl M., Bednář L., Miczán M., Tajč L.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2014

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nr 146

79--87

EN

The results of experiments performed on a 5-stage steam turbine are presented. Operating parameters close to the real design parameters are simulated. The modes with the slightly different input temperature and pressure are also considered. Thermodynamic efficiency defined based on the torque moment by measuring on a water brake is compared with efficiency evaluated from the temperatures and pressures. An analysis of velocity ratios and efficiency of individual stages is carried out.

7

Pressure coefficients on the model of SILSOE cube determined by tests in BLWT tunnels

Hubová O., Lobotka P., Konečná L.

Roczniki Inżynierii Budowlanej

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2014

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z. 14

85--90

SK

Článok sa zaoberá stanovením tlakových koeficientov na modeli kocky v mierke 1:30 pomocou experimentov v dvoch odlišných tuneloch s medznou vrstvou (STUBA, VZLU). Výsledky meraní boli porovnané s literatúrou, ktorá uvádza hodnoty tlakových koeficientov meraných priamo na reálnej kocke s hranou 6 m, v Inštitúte SILSOE v Anglicku. Z porovnania získaných výsledkov bola zistená veľmi dobrá zhoda. Cieľom tejto série meraní bolo zistiťparametre medznej vrstvy a presnosť získaných výsledkov v novom veternom tuneli, uvedenom do skúšobnej prevádzky Slovenskou technickou univerzitou v Bratislave. Merania potvrdili, že tento univerzálny tunel dáva výsledky porovnateľné so zabehnutými svetovými veternými tunelmi a že parametre medznej vrstvy sú nastavené správne. Teda výsledky zodpovedajú realite (meraniam urobených in-situ).

8

Hydraulic transients analysis in pipe networks by the method of characteristics (MOC)

Wichowski R.

Archives of Hydro-Engineering and Environmental Mechanics

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2006

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Vol. 53, nr 3

267-291

EN

The paper presents results of an experimental and theoretical study of the hydraulic transients in straight pipes and numerical simulations of unsteady flow in pipe networks. A mathematical model consists of a set of partial differential equations of hyperbolic type, which have been transformed by the method of characteristics into ordinary differential equations which are solved by the predictor-corrector method. Experimental tests have been performed, in order to examine the hydraulic transients phenomenon, in a single straight steel pipe. The experiments were carried out in the hydraulic laboratory of the Institute of Water Supply and Water Engineering, Environmental Engineering Faculty, Warsaw University of Technology. The numerical results show that the presented one dimensional model for a single pipe correctly describes the phenomenon since there is a good agreement with experimental maximum and minimum oscillations. In the paper, selected exemplary equations in a difference form for the pipe networks are also presented. One calculation example is given relating to the complex water-pipe network consisting of 17 loops, 48 pipelines and 33 nodes, supplied by two independent sources. Water-hammer throughout the whole pipeline network was caused by closing the gate valve at mid-point of one selected pipe. The results of the numerical calculations are presented in graphic form with respect to the final cross-sections of pipes.

9

Diagnostics the natural frequencies of the automobile disc and their analysis

Vavro J., Kopecky M., Saga M.

Diagnostyka

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2004

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Vol. 30, T. 2

165--168

EN

The article deals with the analysis of the natural discs frequencies realized by the means of mathematic simulation by the finite elements method, by which the programs AutoCAD and Cosmos M were used. First fifty natural frequencies are presented for the listed type of the steel disc. The experimental measurement for the listed disc type was made by the Doppler vibrometer. The results of the measurement are presented in a graphic form and the measurement was performed in radial and axial direction.

10

Possibility of applying simulation and stress conditions in Mg-alloys

Čech J., Zemčík L.

Archiwum Odlewnictwa

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2001

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R. 1, nr 2

73--78

EN

An automobile wheel was cast of AZ 91 BE alloy, the material used for the mould was bentonite with 5% of sulphur and 1% of boric acid, the material for the cores was furane. Chemical composition of AZ 91 BE: 8.13% Al; 0.61% Zn; 0.24% Mn; the rest was Mg. The temperature field of the wheel casting was measured and the simulation was performed by means of the SIMTEC program. After heat treatment the wheel casting was measured for internal stresses by the strain-gauge method and the respective simulation was performed. Results of experimental measurement and simulation were compared.

PL

Koło samochodowe odlano ze stopu AZ91 BE w formie bentonitowej o zawartości 5% siarki i 1% kwasu borowego oraz rdzeniem furanowym. Skład chemiczny stopu AZ 91 BE: 8.13% Al; 0.61% Zn; 0.24% Mn; reszta Mg. Pole temperatury odlewu koła zmierzono i symulowano używając programu SIMTEC. Po obróbce cieplnej odlewu zmierzono naprężenia wewnętrzne metodą tensowetryczną i przeprowadzono odpowiednią symulację. Wyniki przeprowadzonych eksperymentów i symulacji zostały porównane.