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Measurement of friction coefficient between damping wire and groove
Šnábl, Pavel; Pešek, Luděk; Bula, Vítězslav; Běhálek, V.; Boháč, T.; Tašek, H.
2021 - anglický
Damping wire is being used on railway wheels for noise suppression. It is inserted into a groove of the wheel and dry friction damping reduces vibrations and thus the noise transmitted by the wheel. For increase of durability of the wire, surface treatment of the groove and the ring must be applied to prevent corrosion. Three combinations of diferent surface treatments were studied during reciprocating motion in a set of measurements with diferent frequencies and normal forces to evaluate friction coeficient. Then, those measurements were repeated after a long-time run to evaluate the change of friction coeficient after the wear of the surfaces.
Klíčová slova:
tribology; friction; damping wire
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurement of friction coefficient between damping wire and groove
Damping wire is being used on railway wheels for noise suppression. It is inserted into a groove of the wheel and dry friction damping reduces vibrations and thus the noise transmitted by the wheel. ...
Proceedings of Topical Problems of Fluid Mechanics 2021
Bodnár, T.; Neustupa, T.; Šimurda, David
2021 - anglický
The aim of the conference is to publish and to discuss the latest results of theoretical, experimental and numerical research in fluid mechanics.
Klíčová slova:
experimental fluid mechanics; mathematical modelling; CFD; turbulence; stratified fluid; multiphase flow; vortex structures; supersonic flow
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Proceedings of Topical Problems of Fluid Mechanics 2021
The aim of the conference is to publish and to discuss the latest results of theoretical, experimental and numerical research in fluid mechanics.
Regionální vlaková doprava s vodíkovým pohonem
Gruber, Jan
2021 - český
Česká republika patří k zemím s nejhustší sítí neelektrifikovaných tratí na světě. Jako alternativa k elektrizaci v oblastech malých regionálních tratí mohou sloužit vlaky využívající vodíkové palivové články. Oproti dieselovým jednotkám nabízejí vyšší ekologičnost, oproti jednotkám čistě bateriovým lepší dojezd, nižší hmotnost a odolnost proti klimatickým podmínkám. V zahraničí již existují úspěšné projekty provozu vodíkových vlaků na regionálních tratích. Prezentace se zabývá možnostmi provozu těchto vlaků v Moravskoslezském regionu při využití rozličných zdrojů vodíku, včetně vodíku tzv. zeleného, či purpurového. The Czech Republic is among the countries with the highest density of non-electrified rail network. The alternative to electrification of small regional tracks is utilization of hydrogen fuel-cell trains. Such trains are much cleaner and quieter in comparison with diesel units. They also provide better range, faster refuelling, lower weight and ability to operate in adverse climatic conditions in comparison with solely battery units. There are successful examples of deployment of hydrogen trains in regional train transport in other countries. The presentation analyses possibilities of operating hydrogen trains in Moravian-Silesian region using various sources of hydrogen, including so-called green hydrogen and purple hydrogen.
Klíčová slova:
hydrogen train; rail transport; green hydrogen; purple hydrogen
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Regionální vlaková doprava s vodíkovým pohonem
Česká republika patří k zemím s nejhustší sítí neelektrifikovaných tratí na světě. Jako alternativa k elektrizaci v oblastech malých regionálních tratí mohou sloužit vlaky využívající vodíkové ...
Stanovení mechanických vlastností čokolády při rázovém zatížení
Buchar, Jaroslav; Trnka, Jan; Kober, Jan
2021 - český
Zpráva vznikla na základě Hospodářské smlouvy č. 5/2021 uzavřené s MU v Brně a obsahuje výsledky výzkumu deformačního chování pěti druhů čokolády při zatěžování vysokými rychlostmi deformace řádově 103 s-1. Při výzkumu byly použity především dvě metody, metoda Hopkinsonovy měrné dělené tyče (HMDT) a metoda modifikované Hopkinsonovy tyče, kdy lze dosáhnout vyšších rychlostí deformace. Pozornost je též věnována lomovému chování čokolády při dynamickém tahovém zatěžování. Tento způsob zatěžování vychází z metody HMDT pomocí uspořádání tzv. Brazilského testu. V tomto výzkumu byla použita též vysokorychlostní kinematografie umožňující studovat vznik a rozvoj lomu čokoládového vzorku. Výsledky měření jsou zpracovány v časové i frekvenční oblasti. The report based on the Economic Contract No. 5/2021 with the MU in Brno and contains the results of research of the deformation behavior of five types of chocolate when loaded with high strain rates of the order 103 s-1. Two methods were used in the research, the Split Hopkinson Pressure Bar method (SHPB) and the modified Hopkinson bar method, where higher deformation rates can be achieved. Attention is also focused to the fracture behavior of chocolate under dynamic tensile loading. This method of loading is based on the SHPB method using the arrangement of the so-called Brazilian test. In this research, high-speed cinematography was also used to study the formation and development of the fracture of the chocolate sample. The measurement results are processed in the time and frequency domains.
Klíčová slova:
chocolate; split Hopkinson pressure bar method (SHPB); Brazilian test
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Stanovení mechanických vlastností čokolády při rázovém zatížení
Zpráva vznikla na základě Hospodářské smlouvy č. 5/2021 uzavřené s MU v Brně a obsahuje výsledky výzkumu deformačního chování pěti druhů čokolády při zatěžování vysokými rychlostmi deformace řádově ...
Measurements on KR-D-4 Cascade
Šimurda, David; Radnic, Tomáš
2021 - anglický
This report contains results and evaluation of aerodynamic measurements conducted on a subsonic compressor blade cascade.
Klíčová slova:
compressor blade cascade; experiment; subsonic flow; transonic flow; AVDR
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurements on KR-D-4 Cascade
This report contains results and evaluation of aerodynamic measurements conducted on a subsonic compressor blade cascade.
Measurements on TR-W-4 Cascade
Luxa, Martin; Šimurda, David
2021 - anglický
The report contains results and evaluation of conducted optical /interferometry and schlieren technique) and pneumatic measurements on the transonic profile cascade intenden for root section of rotor turbine blade.
Klíčová slova:
turbine cascade; transonic flow; hub section
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurements on TR-W-4 Cascade
The report contains results and evaluation of conducted optical /interferometry and schlieren technique) and pneumatic measurements on the transonic profile cascade intenden for root section of rotor ...
Flutter methodology using reduced order aeroelastic model
Prasad, Chandra Shekhar; Pešek, Luděk; Šnábl, Pavel
2021 - anglický
The present research project is focused on development of fast and efficient numerical method based on reduced order aeroelastic method (ROAM) for modeling and analysis of \nclassical flutter in the low pressure (LP) stage steam turbine blade. Stability diagram such as aerodynamic damping (AD) of aeroelasticity of cascade of 3D turbine blades used as a prime \ncharacterization factor. In the calculation of the S-curve/AD, the problem of classical flutter formation associated with running waves is considered here. Running waves is simulated by \nthe inter-blade phase shift of the blades in the cascade. Panel method based boundary element flow solver is employed for calculation of unsteady aerodynamic forces. This method is good \ncompromise of speed and accuracy for the estimation of the stability of the blades on a classical flutter. One way loose coupling technique between PM based flow solver and the structural \nmodel. For the structural part modal model synthesis (MMS) method is adopted in the ROAM solver. MMS is adopted to further reduced the computational cost. The ROAM simulated AD \nand pressure distribution over blade is compared high fidelity CFD data on real blade geometry provided by Doosan Skoda Power s.r.o. Furthermore, the ROAM results are also compared \nwith experimentally obtained results on two different linear cascade. The ROAM model shows good agreement with linear cascade results, however, there is noticeable discrepancy with real blade CFD results.
Klíčová slova:
reduced order model (ROM); classical flutter; steam turbine blade; panel method
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Flutter methodology using reduced order aeroelastic model
The present research project is focused on development of fast and efficient numerical method based on reduced order aeroelastic method (ROAM) for modeling and analysis of \nclassical ...
Modelling approaches to the stress wave propagation in a cracked specimen
Kruisová, Alena; Kopačka, Ján; Kober, Jan
2021 - anglický
One of the essential tasks of non-destructive testing is to detect a crack in a specimen. It is well known that a component with a crack exposed to a harmonic excitation of a given frequency\nhas a nonlinear response as a function of the excitation amplitude. The focus of this paper is the numerical modelling of this phenomenon using the finite element method with the consideration\nof the contact constraint at the crack interface. In addition to the nonlinear transient dynamic problem solved by explicit time integration, a more efficient procedure based on the harmonic\nbalance method is developed. The results of numerical simulations are also compared with experimentally obtained data.
Klíčová slova:
finite element method; contact; crack; harmonic balance method
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Modelling approaches to the stress wave propagation in a cracked specimen
One of the essential tasks of non-destructive testing is to detect a crack in a specimen. It is well known that a component with a crack exposed to a harmonic excitation of a given frequency\nhas a ...
Development of autonomous experimental setup to investigate directional distortional hardening under biaxial loading
Svárovský, Jiří; Parma, Slavomír; Štefan, Jan; Ciocanel, C.; Feigenbaum, H. P.; Klepač, Vilém; Marek, René; Plešek, Jiří
2021 - anglický
Plastic deformations alter the shape of the yield surface in the stress space. Models for predicting the shape of the yield surface according to the direction of loading are being developed. Experimental data are the key factor in development and validation of phenomenological models, such as the model of directional distortional hardening cited in this study. The objective of this paper is to present the experimental setup for investigation of the directional distortional hardening. A new autonomous method was developed using an axial-torsional testing machine and the Labivew 2017 graphical programming environment to monitor the yield surface in axial stress – shear stress space. A suitable yield condition in form of effective plastic strain was used for the determination of the yield points. Initial yield surface obtained by this method shows promising agreement with von Mises model of the yield surface. Several outstanding yield points were measured which disrupt the assumption of the yield surface convexity. Therefore, possible shortcomings caused by the methodology are being investigated.
Klíčová slova:
directional distortional hardening; yield surface; strain hardening; Labview
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Development of autonomous experimental setup to investigate directional distortional hardening under biaxial loading
Plastic deformations alter the shape of the yield surface in the stress space. Models for predicting the shape of the yield surface according to the direction of loading are being developed. ...
Recent improvements in CFD solver for fully coupled particle-laden flows
Šourek, M.; Isoz, Martin
2021 - anglický
While new methods combining the computational fluid dynamics (CFD) and the discrete element method (DEM) have been developed to simulate freely moving solid particles, they tend to be focused on simulations with spherical particles only. Here, we present a strongly coupled CFD-DEM solver capable of simulating movement of arbitrarily-shaped particles dispersed in a fluid. The particles are assumed to be large enough to affect the fluid flow and distributed densely enough to come into contact with both the boundaries of the computational domain and with each other. In this paper, we will focus on the recent improvements of our solver, specifically, in the areas of (i) inclusion of solid bodies into the computational domain, (ii) general CFD-DEM coupling algorithm, and (iii) code parallelization and practical usability.
Klíčová slova:
CFD; DEM; HFDIB-DEM; OpenFOAM
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Recent improvements in CFD solver for fully coupled particle-laden flows
While new methods combining the computational fluid dynamics (CFD) and the discrete element method (DEM) have been developed to simulate freely moving solid particles, they tend to be focused on ...
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