scholarly journals Numerical algorithm for searching for layouts of electroelastic bodies with external electric circuits for obtaining the best damping properties

2020 ◽  
pp. 108-124
Author(s):  
N. A Iurlova ◽  
D. A Oshmarin ◽  
N. V Sevodina ◽  
M. A Iurlov
Keyword(s):  
Natural Vibration ◽  
Mathematical Formulation ◽  
Piezoelectric Element ◽  
Electric Circuit ◽  
Problem Solution ◽  
Vibration Frequencies ◽  
Damping Properties ◽  
Natural Vibrations ◽  
Electric Circuits ◽  
Continuous Frequency

This paper presents an algorithm which allows finding such layouts of electromechanical systems that provide the best vibration damping whether for one mode or a set of vibration modes within some continuous frequency ranges. The basis for the algorithm is the problem solution about natural vibrations. An elastic structure with a piezoelectric element located on its surfaces, which electrodes are connected to a passive external electric circuit, is treated as an electromechanical system. The piezoelectric elements shunted with an electric circuit are the devices where energy dissipation occurs, thus leads to damping of vibrations. A change in damping properties of such systems can be reached by a proper choice of parameters of the electric circuits and corresponding location of the piezoelectric element, which provides the highest energy withdrawal into the electric circuit. The paper presents the mathematical formulation of the natural vibrations problem for piecewise-homogeneous electroelastic bodies shunted with passive external electric circuits. Within the proposed mathematical statement, the problem solution of natural vibrations for such objects is based on values of complex natural vibration frequencies. Real parts of the complex natural vibration frequencies are the circular frequency of vibrations, and the imaginary parts are the damping indices of vibrations. We proposed techniques aimed at determining the location of the piezoelectric element and selecting parameters of shunting the external electric circuit. These approaches are based on values of the complex natural vibration frequencies obtained as results of solving the natural vibrations problem. The proposed approach is demonstrated using a specimen of a thin-walled shell in the semi-cylinder form. The piezoelectric element has a form of a segment of a ring made of PZT-4 piezoceramics. Electrodes of the piezoelectric element are connected to the series resonant RL -circuit. The formulated problem is solved numerically using the finite element method and ANSYS commercial package.

scholarly journals Natural Vibrations of Repetitive Structures

2000 ◽  
Vol 16 (2) ◽  
pp. 85-95 ◽  
Author(s):  
Dajun Wang ◽  
C.-C. Wang
Keyword(s):  
Eigenvalue Problem ◽  
Natural Vibration ◽  
Eigenvalue Problems ◽  
Vibration Frequencies ◽  
Natural Vibrations

ABSTRACTNatural vibration frequencies and modes of repetitive structures, including symmetric, periodic, linking structures, are considered in this work. By using the repetition of the identical parts, we reduce the eigenvalue problem of the structure to a set of eigenvalue problems of lower dimensions associated with the parts. Special forms and properties of the modes of natural vibrations are observed.

Development of an electrical analogue for modeling natural vibrations of a viscoelastic structure with piezoelectric element

2021 ◽  
Vol 32 (3) ◽  
pp. 369-384
Author(s):  
Dmitrii Oshmarin ◽  
Nataliya Sevodina ◽  
Nataliia Iurlova ◽  
Maksim Iurlov
Keyword(s):  
Piezoelectric Element ◽  
Problem Formulation ◽  
Electromechanical System ◽  
Model Parameters ◽  
Electrical Model ◽  
Natural Vibrations ◽  
Viscoelastic System ◽  
Electric Circuits ◽  
Viscoelastic Structure ◽  
Lumped Parameters

This paper focuses on the development of an equivalent electrical model with lumped parameters capable of describing the natural vibrations of an electromechanical system comprising a viscoelastic structure with a piezoelectric element attached to its surface. The important advantage of the model is that it takes into account the energy losses associated with the viscoelastic properties of the material of the main structure. Two versions of the equivalent electric analogue of the initial electro-viscoelastic system in the form of electric circuits, the elements of which are described by the real or complex quantities, are considered. The approaches to the formulation of the problem of natural vibrations in the developed electric analogue are based on Kirchhoff’s laws for electric circuits and Ohm’s law for alternating current. Special attention is paid to the identification of model parameters. A procedure for determining the parameters for the equivalent electrical model is based on the results gained from the solution of a coupled problem of natural vibrations of the initial electromechanical system; problem formulation is also given here. The effectiveness and reliability of the developed equivalent electric models with lumped parameters for the determination of complex eigenfrequencies of the electromechanical system containing energy dissipation elements are demonstrated by analyzing the behavior of structures in the form of a rectangular plate and a semi-cylindrical shell.

scholarly journals Research into the dynamics of radio telescope foundationsusing laser vibration measuring equipment

2020 ◽  
Vol 10 (3) ◽  
pp. 420-427
Author(s):  
Vladimir I. Sobolev ◽  
◽  
Tatiana N. Chernigovskaya ◽  
Keyword(s):  
Radio Telescope ◽  
Measuring Equipment ◽  
Natural Vibration ◽  
Fourier Transforms ◽  
Process Analysis ◽  
Laser Vibrometer ◽  
Contact Method ◽  
Vibration Frequencies ◽  
Natural Vibrations ◽  
Vibration Measuring

This study presents a technology for determining the dynamic parameters of the foundation structures of radio telescopes by a non-contact method based on the use of laser vibration measuring equipment. The main results of a dynamic process analysis are described. The research was carried out in the form of microdynamic tests of foundation structures with the determination of natural oscillation periods based on lower vibrational forms. Measurements of natural vibrations of radio telescope foundations under applied shock were performed, followed by spectral mapping of vibrational processes. The tests were carried out using a tachometric laser vibrometer RSV-150 included in the register of vibration measuring equipment in Russia. Spectral mappings were obtained using Fourier transforms implemented in software packages of the hardware developers. The dynamic features of radio tele-scope foundations are formalized in the form of spectral maps of the initial records of vibrational proc-esses. The method of microdynamic tests using a vibration meter is presented, along with the principles of its operation and the sequence of numerical processing of records of dynamic processes imple-mented on a personal computer using frequency displays of natural vibrations of structures. The values of natural vibration frequencies obtained as a result of measurements confirmed the rigidity and integ-rity of foundation piles. Pronounced solitary peaks of natural vibration frequencies point to the form of natural vibrations of structures as single-mass systems with the absence of deformational forms of vi-brations in the foundation body.

Simplified characteristics of active magnetic bearings

2002 ◽  
Vol 216 (5) ◽  
pp. 623-628 ◽  
Author(s):  
D J Peel ◽  
C M Bingham ◽  
Y Wu ◽  
D Howe
Keyword(s):  
Natural Vibration ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Viscous Damping ◽  
Vibration Frequencies ◽  
Active Magnetic Bearings ◽  
Complex Dynamic ◽  
Speed Range ◽  
Constant Coefficients ◽  
System Characteristics

Traditionally, active magnetic bearing (AMB) systems are designed as an integral component of machines having generally complex dynamic characteristics. An AMB supported rotor has been tested over a speed range that included system natural vibration frequencies. A linear stiffness and viscous damping AMB characteristic with constant coefficients was identified which was independent of the overall system characteristics and which can thus provide simple and transferable data for a machine designer.

scholarly journals TECHNIQUE AND DEVICE FOR THE EXPERIMENTAL ESTIMATION OF THE ACOUSTIC IMPEDANCE OF VISCOELASTIC MEDIUM

2017 ◽  
Vol 8 (4) ◽  
pp. 314-326 ◽  
Author(s):  
O. V. Murav’eva ◽  
V. V. Murav’ev ◽  
D. V. Zlobin ◽  
O. P. Bogdan ◽  
V. N. Syakterev ◽  
...  
Keyword(s):  
Acoustic Impedance ◽  
Experimental Evaluation ◽  
Piezoelectric Element ◽  
Electric Circuit ◽  
Biological Tissues ◽  
Ultrasonic Waves ◽  
Acoustic Parameters ◽  
Laboratory Equipment ◽  
Viscoelastic Media ◽  
Silicone Sealant

Measuring the characteristics of process fluids allows us to evaluate their quality, biological tissues – to differentiate healthy tissues and tissues with pathologies. Measuring the characteristics of process fluids allows us to evaluate their quality, biological tissues – to differentiate healthy tissues and tissues with pathologies. One of the complex acoustic parameters is the impedance, which allows one to fully evaluate the characteristics of viscoelastic media. Most of impedance methods of measurements require using two or more reference media and the availability of calibrated acoustic transducers. The aim of this work ware introduced a methods and construction for the experimental evaluation of the longitudinal and shear impedance of viscoelastic media based on measuring the parameters of the amplitude-frequency characteristics and calculating the elements of the electric circuit for replacing the piezoelectric element which vibrating in the test medium.The paper introduces a methods and construction of the experimental evaluation of the impedances of viscoelastic media. The suggested methods is allowed measuring longitudinal and shear impedances and determining velocities of longitudinal and transverse ultrasonic waves and the values of the elastic moduli of viscoelastic media, including in various aggregate states. The technique is fairly simple to implement and can be reproduced using simple laboratory equipment.The obtained values of the acoustic impedances of the investigated media are in satisfactory agreement with their reference data. In contrast to the known methods for determining the acoustic impedance, the developed technique allows us to estimate with sufficient accuracy the parameter of the shear impedance of viscoelastic media that is difficult to measure at the frequencies of the megahertz range, which determines the shear modulus of the material and characterizes its resistance to shear deformations. The results of the implementation of the developed technique for the estimation of acoustic parameters for a number of media with zero shear elasticity (alcohol, acetone) and viscoelastic media (glycerin, architectural clay, silicone sealant and glue МР-55 before and after polymerization) are presented.

scholarly journals Sequential Reasoning in Electricity: Developing and Using a Three-Tier Multiple Choice Test

2017 ◽  
Vol 8 ◽  
Author(s):  
Hildegard Urban
Keyword(s):  
Multiple Choice ◽  
Electric Circuit ◽  
Choice Test ◽  
School Students ◽  
Reliable Measure ◽  
Electric Circuits ◽  
Multiple Choice Tests ◽  
Qualitative Understanding ◽  
In Series ◽  
Testing Electricity

Electricity is one of the areas in physics most studied in terms of learning difficulties. Misconceptions are strongly-held, stable cognitive structures, which differ from expert conception and affect how students understand scientific explanations. Therefore, there is a need for tests of conceptual understanding tests which are useful in diagnosing the nature of students’ misconceptions related to simple electric circuits and, in consequence, can serve as a valid and reliable measure of students’ qualitative understanding of simple electric circuits. As ordinary multiple choice tests with one-tier may overestimate the students’ correct as well as wrong answers, two- and three-tier tests were developed by researchers. Although, there is much research related to students’ conceptions in basic electricity, there is a lack of instruments for testing basic electricity concepts of students at grade 7, especially addressing an electric circuit as a system for a simple circuit of resistors and lamps in series. To address this gap, the context of the present study is an extension to the development of an already existing instrument developed by the author for testing electricity concepts of students at grade 7, specifically focusing on only two specific aspects in depth: first, to develop three-tier items for figuring out sequential reasoning, and second, to distinguish between misconceptions and lack of knowledge. The participants of the study included 339 secondary school students from grade 7 to 12 after instruction on electricity. Surprisingly, there are no dependences on students’ misconceptions either according to their gender or to their age. In conclusion, the findings of the study suggest that four items for uncovering students’ sequential reasoning can serve as a valid and reliable measure of students’ qualitative understanding of the systemic character of an electric circuit.

The Development of Physics Education Game on Direct Current Electric Circuit for Learners

2021 ◽  
Vol 1 (1) ◽  
pp. 50-62
Author(s):  
Jati Zen Ma'ruf
Keyword(s):  
Direct Current ◽  
Physics Education ◽  
Electric Circuit ◽  
Student Response ◽  
Educational Game ◽  
Average Score ◽  
Distribution Data ◽  
Response Sheet ◽  
Physics Learning ◽  
Electric Circuits

This study is the research of the development of physics education game application. This study has two purposes, namely to (1) developing multimedia for physics learning in the form of a physics education game on direct current electric circuits, (2) knowing the quality of educational game applications that have been produced according to experts, (3)knowing the user's (student's) response to the media of physics learning in the form of educational game applications related to direct current electrical circuit. The development procedure in this study refers to the Luther-Sutopo procedure consisting of the stage of concept, design, material collecting, assembly, testing, and distribution. Data collection techniques in the research in this study using a questionnaire. The research instrument in this study was a validation and assessment sheet which was adapted from the rubric for evaluating C. Stewart's educational game, student response sheets, and the game tester response sheet. Product validation and assessment uses a Likert scale with 4 scales and students' responses use the Guttman scale, while the game tester response sheet uses descriptive analysis. The results of this study are products in the form of simulation physics education game applications in direct current electric circuits, the results of the validation and assessment of material experts and media experts, the educational game application scored 3.8 and 3.3 in a very good category. The results of the user’s (student’s) response to the direct current electric circuit educational game application developed got an average score of 0.97 with the agreed category.

Influence of Gravity and Taper on the Vibration of a Standing Column

2012 ◽  
Vol 4 (04) ◽  
pp. 483-495 ◽  
Author(s):  
C. Y. Wang
Keyword(s):  
Cross Section ◽  
Numerical Stability ◽  
Natural Vibration ◽  
Vibration Frequencies ◽  
Stability Criteria ◽  
Initial Value ◽  
Vertical Column ◽  
Stability Boundaries ◽  
Section Shape ◽  
The Stability

AbstractThe stability and natural vibration of a standing tapered vertical column under its own weight are studied. Exact stability criteria are found for the pointy column and numerical stability boundaries are determined for the blunt tipped column. For vibrations we use an accurate, efficient initial value numerical method for the first three frequencies. Four kinds of columns with linear taper are considered. Both the taper and the cross section shape of the column have large influences on the vibration frequencies. It is found that gravity decreases the frequency while the degree of taper may increase or decrease frequency. Vibrations may occur in two different planes.

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