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Verification of our deformation member for measuring axial force under torsional dynamic load
Šulc, Petr; Pešek, Luděk; Štěpánek, Ivo; Šnábl, Pavel; Bula, Vítězslav
2021 - English
This paper deals with experimental testing of hard rubbers under torsional harmonic loading on an axial torsional servohydraulic testing machine Instron 8852. In evaluating these experiments, we focused on obtaining axial forces and elongation, which is a confirmation of the so-called Poynting effect under torsional loading. An important result from these experiments is a comparison of axial forces from this device with the results from our designed and assembled torsion device with a deformation member for measuring axial forces, which brings us some verification of this device.
Keywords:
axial force; torsion dynamic load; hard rubber; Poynting effect
Available at various institutes of the ASCR
Verification of our deformation member for measuring axial force under torsional dynamic load
This paper deals with experimental testing of hard rubbers under torsional harmonic loading on an axial torsional servohydraulic testing machine Instron 8852. In evaluating these experiments, we ...
Numerical simulation of dynamic loading of a test blade in forced torsional vibration
Šidlof, P.; Vomáčko, V.; Lepičovský, Jan; Šimurda, David; Štěpán, M.; Luxa, Martin
2021 - English
Within a new project focused on blade flutter research, building on previous experience with the NASA Transonic Flutter Cascade facility, static blade cascade and airfoil flutter experiments realized in cooperation between the Institute of Thermomechanics and Technical University of Liberec, a new test facility is under development for the investigation of high subsonic and transonic flow in a blade cascade under forced torsional oscillation. Apart from aerodynamic loading of the blades, the oscillating blade will be exposed to significant structural stresses due to the highfrequency torsional vibration. In order to avoid structural integrity issues from high-cycle fatigue, a numerical simulation of the stress and displacement of the blade was realized. Regions where equivalent stress reaches maximum values were identified, and elastic deformations were computed. The limits in oscillation amplitude and frequency for the safe operation of the experimental setup were discussed.
Keywords:
blade flutter; structural analysis; torsional vibration
Available at various institutes of the ASCR
Numerical simulation of dynamic loading of a test blade in forced torsional vibration
Within a new project focused on blade flutter research, building on previous experience with the NASA Transonic Flutter Cascade facility, static blade cascade and airfoil flutter experiments realized ...
A simple algorithm for probes positioning in BTT systems
Tchawou Tchuisseu, Eder Batista; Procházka, Pavel; Maturkanič, Dušan
2020 - English
The Blade Tip Timing (BTT), a non-contact method for measuring the blade tip displacement through the time of arrival, is studied in this article. This work proposes a simple algorithm based on the minimization of the coherence and the condition number of the sensingmatrix for defining the best probe positioning in the case of synchronous and asynchronous vibrations.
Keywords:
BTT systems; probe positioning; condition number; coherence
Available at various institutes of the ASCR
A simple algorithm for probes positioning in BTT systems
The Blade Tip Timing (BTT), a non-contact method for measuring the blade tip displacement through the time of arrival, is studied in this article. This work proposes a simple algorithm based on the ...
Comparison of power control method for B4 converter connected to unbalanced grid
Šimek, Petr; Valouch, Viktor
2020 - English
The aim of the paper is to present a power control of a three-phase inverter with only four inverter legs (connections B4) connected to an unbalanced grid. The results obtained by the predictive power control with a finite set of control values, the results obtained using a modified direct power control strategy, and the results obtained using a generalized predictive control are compared and discussed.\n
Keywords:
power control; B4 converter; unbalanced grid
Available at various institutes of the ASCR
Comparison of power control method for B4 converter connected to unbalanced grid
The aim of the paper is to present a power control of a three-phase inverter with only four inverter legs (connections B4) connected to an unbalanced grid. The results obtained by the predictive power ...
Contribution to HPC FEM calculations of bladed disk dynamics with dry-friction contacts
Pešek, Luděk; Šnábl, Pavel; Bula, Vítězslav
2020 - English
The experimental set-up for studying dynamical behaviour of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with tie-bosses based on 3D finite element method with surface to surface dry-friction contact model is proposed. Comparison of experimental and preliminary numerical results of dynamical behaviour and damping estimation of our bladed wheel design yielded a reasonable agreement. Due to dry-friction contacts and non-linear solution of 3D FE model it, however, leads to HPC computations and long computation times. The contribution deals with description of computational strategy for damping evaluation and achieved results, too.
Keywords:
bladed wheel; dry-friction contacts; damping; tie-boss couplings
Available at various institutes of the ASCR
Contribution to HPC FEM calculations of bladed disk dynamics with dry-friction contacts
The experimental set-up for studying dynamical behaviour of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with ...
Design of experiment for temperature dependence of rubber samples under torsional harmonic load
Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Košina, Jan; Cibulka, Jan
2020 - English
This work deals with the preparation and methodology of temperature measurement inside the rubber sample. There is a design of a rubber sample with placed temperature sensors and a description with a scheme of temperature measurement under torsional dynamic stress. The reason for these measurements is to determine the temperature dependence and sensitivity of the parameters of the thermal outputs.
Keywords:
heat flow; temperature; Fourier equation
Available at various institutes of the ASCR
Design of experiment for temperature dependence of rubber samples under torsional harmonic load
This work deals with the preparation and methodology of temperature measurement inside the rubber sample. There is a design of a rubber sample with placed temperature sensors and a description with a ...
Experimental modelling of vibroacoustics of the human vocal tract with compliant walls
Radolf, Vojtěch; Horáček, Jaromír; Košina, Jan
2020 - English
Experimental model of human vocal tract cavities with hard walls has been modified to take into account the compliance of the soft tissue of the human vocal tract. The paper presents the studied acoustic-structural interaction of the vocal tract cavities with a dynamical system originated in vibration of the soft tissue. The experimental results are in qualitative agreement with the results of mathematical modelling. Compliant walls of acoustic cavities generate additional low frequency acoustical-mechanical resonances of the system and increase acoustic resonance frequencies.
Keywords:
biomechanics of voice; vocal tract acoustics; acoustic-structural interaction.
Available at various institutes of the ASCR
Experimental modelling of vibroacoustics of the human vocal tract with compliant walls
Experimental model of human vocal tract cavities with hard walls has been modified to take into account the compliance of the soft tissue of the human vocal tract. The paper presents the studied ...
Dependence of signal strangth on the radial distance and different types of magnets
Procházka, Pavel; Voronova, Evgeniya; Maturkanič, Dušan
2020 - English
The paper describes dependence of signal strength on the radial distance between the sensor and the measured object and dependence of signal strength on the different types of magnets. The measurements were performed in the laboratory of the rotational laser vibrometry originated at the Institute of Thermomechanics AS CR, v.v.i.
Keywords:
vibration; diagnostics; sensor; laser; blade; turbine
Available at various institutes of the ASCR
Dependence of signal strangth on the radial distance and different types of magnets
The paper describes dependence of signal strength on the radial distance between the sensor and the measured object and dependence of signal strength on the different types of magnets. The ...
Inverse mass matrix for higher-order finite element method in linear free-vibration problems
Kolman, Radek; González, J.G.; Cimrman, Robert; Kopačka, Ján; Cho, S.S.; Park, B.G.
2020 - English
In the paper, we present adirect inverse mass matrix in the higher-orderfinite element method forsolid mechanics. The direct inverse mass matrix is sparse, has the same structure as the consistent mass matrixand preserves the total mass. The core of derivation of the semi-discrete mixed form is based on the Hamilton’s principle of leastaction. The cardinal issue is finding the relationship between discretized velocities and discretized linear momentum. Finally, the simple formula for the direct inversemass matrix is presented as well as thechoice of density-weighted dual shape functions for linear momentum with respect to the displacement shape functionwith achoice of the lumping mass method for obtaining the correct and positive definitive velocity-linear momentum operator. The application of Dirichlet boundaryconditions into the direct inversemass matrix forafloating system is achieved usingthe projection operator. The suggested methodology is tested on a free-vibration problem of heterogeneous bar for different ordersof shape functions.
Keywords:
higher-order finite element method; direct inverse mass matrix; consistent and lumped massmatrix; free vibration problem; heterogeneous bar
Available at various institutes of the ASCR
Inverse mass matrix for higher-order finite element method in linear free-vibration problems
In the paper, we present adirect inverse mass matrix in the higher-orderfinite element method forsolid mechanics. The direct inverse mass matrix is sparse, has the same structure as the ...
Anomalies detection in time-series data for the internal diagnostics of autonomous mobile robot
Věchet, Stanislav; Krejsa, Jiří; Chen, K.S.
2020 - English
Autonomous mobile robots are complex mechatronic machines which consists of numerous hardware and software modules working asynchronously to achieve desired behaviour. As there are many frameworks which helps to overcome the flat learning curve the problem of internal diagnostics arises. While users and developers are able to focus only on solving the high level problem algorithm or methods the internal states of the system is hidden. This helps to separate the users from solving hardware issues, which is helping until everything works properly. We present an algorithm which is able to detect anomalies in time based behaviour of the robot to improve the users confidence that the internal robot framework works correctly and as desired. The algorithm is based on probabilistic patterns detection based on Bayesian probabilistic theory.
Keywords:
anomalies detection; system diagnostic; robot operating system
Available at various institutes of the ASCR
Anomalies detection in time-series data for the internal diagnostics of autonomous mobile robot
Autonomous mobile robots are complex mechatronic machines which consists of numerous hardware and software modules working asynchronously to achieve desired behaviour. As there are many frameworks ...
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