No (1755)
Yes (80)
Number of found documents:
1835
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Acoustic resonances can support self-oscillations of a dynamic system.
Horáček, Jaromír; Radolf, Vojtěch; Košina, Jan; Laukkanen, A. M.
2021 - English
Flutter instability of human vocal folds is a necessary condition for speaking, because airflow induced vibrations of the vocal folds create the voice source. The present study shows that the vocal fold self-oscillations can be strongly influenced by interaction with acoustic resonances of the human vocal tract.
Keywords:
biomechanics of voice; modelling of human voice
Available at various institutes of the ASCR
Acoustic resonances can support self-oscillations of a dynamic system.
Flutter instability of human vocal folds is a necessary condition for speaking, because airflow induced vibrations of the vocal folds create the voice source. The present study shows that the vocal ...
Identification of dynamic properties of built electrodynamic shaker
Šnábl, Pavel; Kozánek, Jan; Pešek, Luděk
2021 - English
Electrodynamic shaker was built in our institute for excitation of vibrating blade in a flow field. The shaker consists of permanent magnet and voice coil, 3D printed body, core and cover, and two at suspension rings laser-cutted from Pertinax. For simulation purposes of the whole system, identfication of shaker dynamic parameters was needed. Several identification methods in time or frequency domain were used, and it was shown that the shaker model must contain nonlinear stiffness in order to describe the real system more accurately.
Keywords:
identification; dynamics; shaker
Available at various institutes of the ASCR
Identification of dynamic properties of built electrodynamic shaker
Electrodynamic shaker was built in our institute for excitation of vibrating blade in a flow field. The shaker consists of permanent magnet and voice coil, 3D printed body, core and cover, and two at ...
Measurement of friction coefficient between damping wire and groove
Šnábl, Pavel; Pešek, Luděk; Bula, Vítězslav; Běhálek, V.; Boháč, T.; Tašek, H.
2021 - English
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.
Keywords:
tribology; friction; damping wire
Available at various institutes of the ASCR
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 - English
The aim of the conference is to publish and to discuss the latest results of theoretical, experimental and numerical research in fluid mechanics.
Keywords:
experimental fluid mechanics; mathematical modelling; CFD; turbulence; stratified fluid; multiphase flow; vortex structures; supersonic flow
Available at various institutes of the ASCR
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.
Macroscopic constitutive model for NiTi shape memory alloys: Formulation, numerical imple-mentation, and application in materials research
Frost, Miroslav; Sedlák, Petr
2021 - English
In this contribution, we present a constitutive model for shape memory alloys formulated within the generalized standard materials framework. It provides substantial flexibility for the development of constitutive equations. On the other hand, finding the optimal numerical solution procedure for the resulting systems of evolutionary inclusions can be challenging. We present our approach and illustrate the capabilities of the model on several numerical simulations compared with experiments.
Keywords:
shape memory alloys; modeling
Fulltext is available at external website.
Macroscopic constitutive model for NiTi shape memory alloys: Formulation, numerical imple-mentation, and application in materials research
In this contribution, we present a constitutive model for shape memory alloys formulated within the generalized standard materials framework. It provides substantial flexibility for the development of ...
Measurements on KR-D-4 Cascade
Šimurda, David; Radnic, Tomáš
2021 - English
This report contains results and evaluation of aerodynamic measurements conducted on a subsonic compressor blade cascade.
Keywords:
compressor blade cascade; experiment; subsonic flow; transonic flow; AVDR
Available at various institutes of the ASCR
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 - English
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.
Keywords:
turbine cascade; transonic flow; hub section
Available at various institutes of the ASCR
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 - English
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.
Keywords:
reduced order model (ROM); classical flutter; steam turbine blade; panel method
Available at various institutes of the ASCR
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 - English
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.
Keywords:
finite element method; contact; crack; harmonic balance method
Available at various institutes of the ASCR
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 - English
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.
Keywords:
directional distortional hardening; yield surface; strain hardening; Labview
Available at various institutes of the ASCR
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. ...
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