Number of found documents: 1819
Published from to

Dynamics of a cantilever beam with piezoelectric sensor: Experimental study
Kolman, Radek; Kylar, Jaromír; Kotek, Vojtěch; Cimrman, Robert; Musil, Ladislav
2023 - English
Online and real-time sensing and monitoring of the health state of complex structures, such as air-craft and critical parts of power stations, is an essential part of the research in dynamics. Several types of sensors are used for sensing dynamic responses and monitoring response changes during the operation of critical parts of complex systems. The piezoelectric (PZ) materials belong to one group of electroactive materials, which transform mechanical deformation into an electrical response. For example, PZ ceramics or PVDF foils are employed for online sensing of the time history of mechanical deformation. Experimentally obtained response of a cantilever beam structure with a glued PZ sensor is the case of interest in this contribution. During the transient problem of the beam loaded by suddenly interrupted load due to the weight of a mass at the end of the beam, the time history of normal velocity at a point on the beam surface has been measured by a laser vibrometer and parallely, the output voltage on the PZ sensor has been measured by an electric device. The experimental data in the case of the first eigen-frequency is in good agreement with the value given by the formulae from the theoretical modeling of free vibration of a linear beam. Keywords: dynamics of beam-like structure; piezo-electric material; sensing of dynamic response; structural Health Monitoring; laser vibrometer measurement Fulltext is available at external website.
Dynamics of a cantilever beam with piezoelectric sensor: Experimental study

Online and real-time sensing and monitoring of the health state of complex structures, such as air-craft and critical parts of power stations, is an essential part of the research in dynamics. Several ...

Kolman, Radek; Kylar, Jaromír; Kotek, Vojtěch; Cimrman, Robert; Musil, Ladislav
Ústav termomechaniky, 2023

Direct construction of reciprocal mass matrix and higher order fininite element method
Cimrman, Robert; Kolman, Radek; González, J. A.; Park, K. C.
2023 - English
When solving dynamical problems of computational mechanics, such as contact-impact problems or cases involving complex structures under fast loading conditions, explicit time-stepping algorithms are usually preferred over implicit ones. The explicit schemes are normally combined with the lumped (diagonal) mass matrix so that the calculations are efficient and moreover dispersion errors in wave propagation are partially eliminated. As an alternative to lumping with advantageous properties, the reciprocal mass matrix is an inverse mass matrix that has the same sparsity structure as the original consistent mass matrix, preserves the total mass, captures well the desired frequency spectrum and leads thus to efficient and accurate calculations. In the contribution we comment on the usability of the reciprocal mass matrix in connection with higher order FEM. Keywords: higher-order finite element method; reciprocal mass matrix; transient problems; explicit time integration; lumping process Fulltext is available at external website.
Direct construction of reciprocal mass matrix and higher order fininite element method

When solving dynamical problems of computational mechanics, such as contact-impact problems or cases involving complex structures under fast loading conditions, explicit time-stepping algorithms are ...

Cimrman, Robert; Kolman, Radek; González, J. A.; Park, K. C.
Ústav termomechaniky, 2023

Applications of blade vibration measurements in the laboratory of rotational laser vibrometry
Maturkanič, Dušan; Procházka, Pavel; Hodboď, Robert; Mekhalfia, Mohammed Lamine; Voronova, Evgeniya
2023 - English
The Laboratory of Rotational Laser Vibrometry was established at the Institute of Thermomechanics AS CR, v.v.i. in 2015 and the first experiments were started the following year. The measurements are intended for the research of vibration of rotating blades. The paper includes a summary of measurement results using a special turbine model and their consequences in theoretical research, as well as measurements with a real compressor of aircraft engine and comparison with computational analysis. The paper also describes the complex system for measurement and analysis. Keywords: laboratory; turbine; blade; vibration; precision method Available at various institutes of the ASCR
Applications of blade vibration measurements in the laboratory of rotational laser vibrometry

The Laboratory of Rotational Laser Vibrometry was established at the Institute of Thermomechanics AS CR, v.v.i. in 2015 and the first experiments were started the following year. The measurements are ...

Maturkanič, Dušan; Procházka, Pavel; Hodboď, Robert; Mekhalfia, Mohammed Lamine; Voronova, Evgeniya
Ústav termomechaniky, 2023

Experimental and numerical investigation of the frequency-modal properties of the switch box
Zolotarev, Igor; Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel; Gabriel, Dušan; Mračko, Michal; Masák, Jan
2023 - English
The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate modifications. This paper deals with numerical and experimental frequency-modal properties of the switch box and mutual comparison for numerical model validation. Keywords: modal analysis; natural frequencies; eigen-modes of vibration Available at various institutes of the ASCR
Experimental and numerical investigation of the frequency-modal properties of the switch box

The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate ...

Zolotarev, Igor; Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel; Gabriel, Dušan; Mračko, Michal; Masák, Jan
Ústav termomechaniky, 2023

Calibrated finite volume method-based simulation framework for laser shock peening
Isoz, Martin; Gruber, Pavel; Schmidt, Jaroslav; Kubíčková, Lucie; Štefan, Jan; Kaufman, Jan; Brajer, Jan; Gabriel, Dušan
2023 - English
Modern and highly competitive industry seeks components with high strength and fatigue resistance. Both of these properties may be improved by peening of the component surface and the standard peening processes, such as the shot peening, are widely used in both automotive and aerospace industries. The laser shock\npeening (LSP), i.e. hardening of the material surface by a laser-induced shock wave, is a modern alternative to the standard peening. Concurrently, the industrial applications of LSP are promoted by recently emerged affordable high power-density lasers. However, the nascent LSP applications are still mostly a trial-and-error\nprocesses based on an extensive experimental testing. Consequently, we focused on a highly application-driven development of a framework for LSP modeling, and the internal workings and results of which are the focus of the present contribution. Keywords: laser shock peening; modeling; finite volume method; OpenFOAM Fulltext is available at external website.
Calibrated finite volume method-based simulation framework for laser shock peening

Modern and highly competitive industry seeks components with high strength and fatigue resistance. Both of these properties may be improved by peening of the component surface and the standard peening ...

Isoz, Martin; Gruber, Pavel; Schmidt, Jaroslav; Kubíčková, Lucie; Štefan, Jan; Kaufman, Jan; Brajer, Jan; Gabriel, Dušan
Ústav termomechaniky, 2023

Mixing characteristics of a magnetically driven Rushton turbine in an unbaffled stirred tank reactor
Idžakovičová, Kristýna; Haidl, Jan; Gebouský, Ondřej; Isoz, Martin
2023 - English
The standard and well-researched stirred vessel configuration comprises a tank equipped with one or more impellers positioned in the vessel’s axis and multiple wall-mounted baffles preventing the central vortex creation. However, particular industries, such as biotechnology, have an increased need for a sterile environment that often results in the usage of atypical stirred vessel configurations. An example of a commonly equipped atypical stirred vessel is an unbaffled stirred tank with an eccentric magnetically driven impeller. However, there is only a little knowledge about the mixing characteristics of such designs. In this work, we list experimental results for both the standard and atypical stirred vessel configurations. Furthermore, we present a CFD model of the atypical configuration. The model is used to calculate its mixing characteristics that are subsequently compared against our experimental results. It is shown that for the liquid height (H) to the vessel diameter (T) ratio H/T ≲ 1.2, the characteristics of both the standard and atypical designs coincide. For higher liquid heights (i) the characteristics of the atypical design decrease dramatically, and (ii) the characteristics estimates based on approaches developed for the standard configuration become unreliable. Keywords: stirred vessel; eccentric impeller; unbaffled tank; CFD; OpenFOAM; experiment Fulltext is available at external website.
Mixing characteristics of a magnetically driven Rushton turbine in an unbaffled stirred tank reactor

The standard and well-researched stirred vessel configuration comprises a tank equipped with one or more impellers positioned in the vessel’s axis and multiple wall-mounted baffles preventing the ...

Idžakovičová, Kristýna; Haidl, Jan; Gebouský, Ondřej; Isoz, Martin
Ústav termomechaniky, 2023

Engineering Mechanics 2023
Radolf, Vojtěch; Zolotarev, Igor
2023 - English
The proceedings contains papers presented at the 29th International Conference on Engineering Mechanics, which has been held in OREA Resort Devět Skal in Czech Republic under auspices of the Czech Society of Mechanics and being a part of IFTOMM (The International Federation for the Promotion of Mechanism and Machine Science) activities. As it corresponds with character of the conference, this proceedings consists of several topic oriented parts: Biomechanics, Fluid mechanics, Dynamics, Fracture mechanics, Mechatronics, Reliability of structures, Mechanics of solids, Technological processes, Thermodynamics. The volume represents a well-balanced overview of theoretical, numerical and experimental work on fundamental and applied studies. Keywords: biomechanics; dynamics; mechatronics; fluid mechanics; mechanics of solids; fracture mechanics Fulltext is available at external website.
Engineering Mechanics 2023

The proceedings contains papers presented at the 29th International Conference on Engineering Mechanics, which has been held in OREA Resort Devět Skal in Czech Republic under auspices of the Czech ...

Radolf, Vojtěch; Zolotarev, Igor
Ústav termomechaniky, 2023

Measurements on Turbine Cascade KOBRA
Luxa, Martin; Hála, Jindřich; Šimurda, David
2023 - English
The report contains results and evaluation of aerodynamic measurement on a blade cascade representing the section imitating the conical stream line in the last rotor row of a gas trubine under considerable off-design condition. The research report contains detailed specifications of the measured model, overview of the results of the optical measurements (interferometry, schlieren method in Toepler configuration) and pneumatic measurements (traversing with five hole conical probe downstream the cascade). Keywords: turbine cascade; turbine off-design condition; tarnsonic flow Available at various institutes of the ASCR
Measurements on Turbine Cascade KOBRA

The report contains results and evaluation of aerodynamic measurement on a blade cascade representing the section imitating the conical stream line in the last rotor row of a gas trubine under ...

Luxa, Martin; Hála, Jindřich; Šimurda, David
Ústav termomechaniky, 2023

Autonomous vehicles lane detection using particle filters
Věchet, Stanislav; Krejsa, Jiří; Chen, K.S.
2022 - English
Lane detection belongs among many others crucial tasks which an autonomous vehicles traveling in urban roads need to take care of. We present a lane detection method which uses particle filters combined with visual information from onboard camera to control the vehicles direction. Our initial experiments shows promising results as applied and tested in urban roads with focus on real-time data processing. Keywords: mobile robot; signal processing; measurement Available at various institutes of the ASCR
Autonomous vehicles lane detection using particle filters

Lane detection belongs among many others crucial tasks which an autonomous vehicles traveling in urban roads need to take care of. We present a lane detection method which uses particle filters ...

Věchet, Stanislav; Krejsa, Jiří; Chen, K.S.
Ústav termomechaniky, 2022

Mobile Robot in the Elevator: What Floor Am i On?
Krejsa, Jiří; Věchet, Stanislav; Chen, K.S.; Havelka, M.; Černil, M.
2022 - English
Wheeled mobile robots in multiple stories buildings have to use elevator to access arbitrary floor of the building. To do so, the control system must be able to detect and access elevator controls and also determine on which floor the elevator stopped. The paper deals with the latter problem, using the fusion of relative floor change detected by onboard accelerometer and absolute floor number detected by the processing of elevator information screen panel image acquired by onboard camera. Bayesian filter is used for data fusion and convolution neural network for image processing. Field tests resulted in 97% correct detection. Keywords: mobile robot; elevator floor determination; Bayesian filtering Available at various institutes of the ASCR
Mobile Robot in the Elevator: What Floor Am i On?

Wheeled mobile robots in multiple stories buildings have to use elevator to access arbitrary floor of the building. To do so, the control system must be able to detect and access elevator controls and ...

Krejsa, Jiří; Věchet, Stanislav; Chen, K.S.; Havelka, M.; Černil, M.
Ústav termomechaniky, 2022

About project

NRGL provides central access to information on grey literature produced in the Czech Republic in the fields of science, research and education. You can find more information about grey literature and NRGL at service web

Send your suggestions and comments to nusl@techlib.cz

Provider

http://www.techlib.cz

Facebook

Other bases