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Wyszukujesz frazę "natural vibration frequency" wg kryterium: Temat


Tytuł:
Investigations of harbour brick structures by using operational modal analysis
Autorzy:
Żółtowski, M.
Tematy:
modal analysis
natural vibration frequency
stabilization diagram
structural vibrations
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Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:
https://bibliotekanauki.pl/articles/258750.pdf  Link otwiera się w nowym oknie
Opis:
Historic harbour brick objects are subject to large dynamic loads clearly reflected by generated vibration processes. The vibrations may affect state of serviceability of structures by lowering comfort of persons working there as well as possible reaching the level hazardous to safety of the structures. The effect of vibrations to structure is mainly manifested by additional stresses in a given cross-section, which are summed up with those resulting from static loads. Moreover often occur consequences associated with environmental conditions and fatigue of materials which accelerate destruction of the objects. Therefore the dynamic loads may cause damaging effects in buildings of various structural types or even lead to their catastrofic destruction. Judging the necessity of improving the quality assessment methods of building structures for purposes of estimation of their state as well as safety factors for brick structures (see PN-B- 03002 standard, p.3.1.3 and 4.6), the author of this work undertook an attempt to investigate destruction process of selected building structures by using the method of operational modal analysis.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Damping of torsional vibrations of ship engine crankshafts – general selection methods of viscous vibration damper
Autorzy:
Chomik, W.
Tematy:
torsional vibrations
torsional vibration damping
torsional vibration dampers
crankshaft
natural vibration frequency
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Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:
https://bibliotekanauki.pl/articles/260606.pdf  Link otwiera się w nowym oknie
Opis:
This paper describes causes of torsional vibrations generated in ship engine crankshafts. Means for damping the torsional vibrations as well as general methods for selection of viscous torsional vibration dampers for a given type of engine are also presented. Exemplary results of calculations connected with selection of a viscous torsional vibration damper intended for a six-cylinder engine, are attached.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimal design of bar structures with their supports in problems of stability and free vibrations
Autorzy:
Bojczuk, D.
Rębosz-Kurdek, A.
Tematy:
buckling load
natural vibration frequency
optimal layout of supports
topological derivative
finite topology modification
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Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:
https://bibliotekanauki.pl/articles/279197.pdf  Link otwiera się w nowym oknie
Opis:
The problem of maximization of the buckling load and the problem of maximization of the natural vibration frequency under a condition imposed on the global cost is discussed. Cross-sectional areas of bar structures and number of elastic supports, their positions and stiffnesses (or the number and positions of rigid supports) are selected as design parameters. The proposed here algorithm of optimization of bar structures with their supports is applied for analysis of some optimization problems. Illustrative examples confirm applicability of the proposed approach.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical models for the evaluation of natural vibration frequencies of thermo-modernized building walls
Modele numeryczne do oceny częstotliwości drgań własnych ścian budynków po termomodernizacji
Autorzy:
Kuźniar, K.
Zając, M.
Tematy:
model numeryczny
termomodernizacja ścian
częstotliwość drgań własnych
metoda elementów skończonych
MES
numerical model
thermo-modernized wall
natural vibration frequency
finite element method
FEM
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Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/230919.pdf  Link otwiera się w nowym oknie
Opis:
As a result of the necessity to improve energy properties of prefabricated buildings, their thermo-modernizations are performed. In the paper various approaches to the modelling of prefabricated load bearing walls before and after thermo-modernization are presented. Simple one layer models with extra mass from ceilings and equivalent stiffness as well as multilayer ones are taken into consideration using the finite element method software. Values of the natural frequencies of the wall horizontal vibrations calculated using the various models, are compared. It was proved that even the very simple model with equivalent stiffness allows to compute natural vibration frequencies of wall with acceptable accuracy for engineering practice.
W niniejszej pracy pokazano różne podejścia do modelowania prefabrykowanych ścian nośnych przed i po termomodernizacji. Wykorzystując metodę elementów skończonych rozważono proste, jednowarstwowe modele o zastępczej sztywności oraz modele wielowarstwowe. Porównywano częstotliwości ich poziomych drgań własnych. Rozważono wysoką, typową prefabrykowaną ścianę nośną systemu budownictwa prefabrykowanego WWP – 10.8m szerokości i 29.7m (11 kondygnacji x 2.7m) wysokości. Każda płyta prefabrykowana składa się z trzech warstw: nośnej, izolacji cieplnej i elewacyjnej. Dodatkowe warstwy wynikające z termomodernizacji tworzą: zbrojona zaprawa, styropian i siatka z włókien szklanych.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Zagadnienia obliczeń częstości drgań odkuwki wirnika turbogeneratora
Problems of calculations the natural frequency of turbo-generator rotor core
Autorzy:
Przyborowski, W.
Hryciów, Z.
Tematy:
turbogeneratory
wirniki
częstości drgań własnych rdzenia wirnika
turbogenerators
rotors
natural frequency of rotor’s vibration
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Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Napędów i Maszyn Elektrycznych Komel
Powiązania:
https://bibliotekanauki.pl/articles/1199356.pdf  Link otwiera się w nowym oknie
Opis:
The paper presents the problems connected with calculations of the natural frequency of turbo-generator rotor with a nominal power 800 MW. An influence of modifications of magnet's slot-dent zone on natural frequency was analysed. In the first variant, the number of excitation winding slots were changed. In the second case of calculations, the rotor slots were closed with wedges. The basic parameter for calculating the natural vibration of the core of the rotor is the spacing of the turbo-generator bearings.
W pracy rozpatrzono problem częstości drgań własnych odkuwki wirnika turbogeneratora o mocy znamionowej PN = 800 MW. Przeanalizowano również wpływ zmiany struktury żłobkowo-zębowej magneśnicy na jej drgania własne. W pierwszym wariancie zmieniono liczbę żłobków uzwojenia wzbudzającego. W drugim przypadku obliczeń żłobki wirnika zostały zamknięte klinami. Podstawowym parametrem obliczeń drgań własnych rdzenia wirnika jest rozstaw stojaków łożyskowych turbogeneratora. Turbogenerator o określonej mocy można uznać za jednostkę limitacyjną zainstalowanych w kraju turbogeneratorów i charakterystyczną dla tej klasy maszyn pod względem konstrukcyjnym. Należy zauważyć, że turbogeneratory z przedziału wartości mocy <400, …, 1600 MW> nieznacznie różnią się wieloma parametrami konstrukcyjnymi, poza oczywiście wymiarem poosiowym wirników.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new continuous model for flexural vibration analysis of a cracked beam
Autorzy:
Behzad, M.
Ebrahimi, A.
Meghdari, A.
Tematy:
vibration
crack
beam
natural frequency
mode shape
weighted residual
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Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:
https://bibliotekanauki.pl/articles/258914.pdf  Link otwiera się w nowym oknie
Opis:
In this paper a new continuous model for vibration analysis of a beam with an open edge crack is presented. A quasi-linear displacement filed is suggested for the beam and the strain and stress fields are calculated. The equation of motion of the beam is calculated using the Hamilton principle. The calculated equation of motion is solved with a modified weighted residual method and the natural frequencies and mode shapes are obtained. The results are compared with those obtained by finite element method and an excellent agreement has been observed. The presented model is a simple and accurate method for analysis of the cracked beam behavior near or far from the crack tip.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of the multiple damages and temperature changes on the natural frequency
Autorzy:
Mohammadi Esfarjani, S.
Salehi, M.
Ghassemi, A.
Tematy:
structural health monitoring
damage detection
vibration response
temperature
natural frequency
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Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:
https://bibliotekanauki.pl/articles/279351.pdf  Link otwiera się w nowym oknie
Opis:
Damage detection based on structural dynamic characteristics, such as natural frequencies and mode shapes, is an important area of research. Obtaining accurate structural dynamic characteristics is perhaps the most challenging aspect. In particular, changes in environmental temperature due to seasonal weather or radiation from sunshine leads to changes in the dynamic characteristics of structures. An important conclusion is that changes in the dynamic characteristics of a structure due to damage may be smaller than changes in the dynamic characteristics due to variations in temperature. Also, damage can affect the frequency response. This is the first study of evaluation of the effect of changes in temperature and multiple damages on natural frequency at the same time. In this paper, the simultaneous effect of the multiple defects and temperature on the natural frequencies of 6063 aluminum alloy beam are assessed numerically. ABAQUS finite element software is used for the numerical analysis. The present paper aims to evaluate the temperature effect and multiple damages on vibration responses. The variations in the frequency have been analysed in simulation by using an aluminum specimen and obtaining impedance signatures at temperatures ranging from −200◦C to 204◦C. The results show that an increase in temperature leads to a decrease in structural frequency, and that a decrease in temperature leads to an increase in structural frequency. The evaluation of the effect of multiple defects on natural frequency shows that when damages are created in the structure, there is a significant decrease in the natural frequency responses of the 6063 aluminum alloy beam. The results show that damage causes a decrease in the natural frequency of the structure. This study highlights the importance of applying simulation methods to the evaluation of the effect of changes in environmental temperature and multiple damages on the dynamic characteristics such as natural frequencies and mode shapes, especially at the same time.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Improved MSA Model for Evaluating the Sound Transmission Loss of a Rectangular Plate for Diffuse Field Incidence
Autorzy:
Kim, Myong-Jin
Won, Kyong-Su
Ri, Chol-Su
Tematy:
transmission loss
low frequency range
natural vibration mode
diffuse field incidence
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Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:
https://bibliotekanauki.pl/articles/176309.pdf  Link otwiera się w nowym oknie
Opis:
This paper presents an approximate analytical model for estimating the transmission loss (TL) of a finite rectangular plate in the low frequency range, which is based on the modal summation approach (MSA) taking into account the modal radiation impedance and fluid loading. The mode-dependent radiation resistance is calculated using the Rayleigh integral. The fluid loading is taken into account through the natural frequency modified by the added mass. The results are compared with the ones of Statistical Energy Analysis (SEA) coupled with FEM and FEM coupled with BEM. In addition, the effects of the various vibration modes and the fluid loading on TL, and a way for reducing the calculation time are discussed.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on vibration characteristics of motorized spindle at high speed based on power flow
Autorzy:
Bao, Yudong
Zhou, Zhentao
Wu, Linkai
Dai, Ye
Tematy:
harmonic response
motorized spindle
natural frequency
power flow
vibration characteristics
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Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:
https://bibliotekanauki.pl/articles/63161975.pdf  Link otwiera się w nowym oknie
Opis:
To show dynamic properties of a motorized spindle at high speed, C01 type motorized spindle bearing-rotor system is used as a study object, and the dynamic model of the bearing-rotor system is established. The method to analyze vibration characteristics of motorized spindles by power flow is proposed, and it is found that the vibration energy is not necessarily considerable at the position where the vibration displacement response is significant. Finally, the system vibration energy distribution under different bearing stiffness is analyzed. The power flow method can analyze the dynamic characteristics of the bearing-rotor system in terms of energy distribution.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Damage detection in composite cylindrical panels based on forced vibration
Autorzy:
Barski, M.
Pająk, P.
Tematy:
damage detection
forced vibration
natural frequency
composite cylindrical panels
finite element method
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Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/244631.pdf  Link otwiera się w nowym oknie
Opis:
The current work is devoted to the problem of the damage detecting inside the composite cylindrical panels. The applied method is based on the analysis of the forced vibration and corresponding mode shapes of the structure. The presented study has theoretical character (numerical experiment) but it can be easily adopted in practice, for example in case of the SLDV technique. The analysis is performed with use of finite element method. The internal defect is modeled by the reduction of the composite material stiffness and density in arbitrary chosen elements. In the first step the natural frequencies of the intact structure are computed with use of the modal analysis. Next, the corresponding mode shapes are determined (harmonic analysis) for the damage and intact structure. For the each mode shape the curvature in the longitudinal and circumferential direction are determined. Generally, the change of the curvature are very similar in case of damage and intact structure. However, in the location of the damage the change of mode shape curvature are quite different in comparison with intact ones. This fact can be further used in order to detect any kind of flaws inside the analyzed structure. The appropriate damage index is also introduced. Moreover, the simplified analysis of the measurement error influence on the accuracy of the proposed approach is also investigated. The discussed method of the damage detecting in the investigated here multilayered cylindrical panel are very sensitive. Even single small flaws with relatively low reduction of the material stiffness as well as its position can be effectively detected and localized.
Dostawca treści:
Biblioteka Nauki
Artykuł

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