scholarly journals Vibration Simulation of the cylindrical reservoir shell containing fluid vortex with the help of Vib-Shape software

2015 ◽  
Vol 37 ◽  
pp. 194
Author(s):  
Hossein Moradi ◽  
Farzan Barati
Keyword(s):  
Mode Shape ◽  
Vibration Mode ◽  
Mode Shapes ◽  
Vibrational Behavior ◽  
Shell Vibration ◽  
Vibration Simulation ◽  
Different Levels ◽  
Cylindrical Reservoir ◽  
Good Agreement

This paper addresses the simulation of the vibrational behavior of a flat-bottomed cylindrical reservoir in different levels of fluid vortex with the help of Vib-Shape software. The reservoir is equipped with a mixer, which creates fluid vortex and required loading. The compliance of the shell vibration mode shape of the mentioned model obtained from the collected data and simulation in the aforementioned software is compared with the mode shapes derived from the Donnell‘s theory. The results are in the good agreement with the governing theories of the problem.

USE OF MODAL FLEXIBILITY AND NORMALIZED MODAL DIFFERENCE FOR VIBRATION MODE SHAPE EXPANSION

2009 ◽  
Vol 09 (04) ◽  
pp. 765-775 ◽  
Author(s):  
WEI-XIN REN ◽  
BIJAYA JAISHI
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Mode Shape ◽  
Degrees Of Freedom ◽  
Vibration Mode ◽  
Mode Shapes ◽  
Modal Expansion ◽  
Simply Supported ◽  
Modal Flexibility ◽  
Actual Test

Proposed herein are two possible ways for mode shape expansion for future use. The first method minimizes the modal flexibility error between the experimental and analytical mode shapes corresponding to the measured degrees of freedom (DOFs) to determine the multiplication matrix. In the second method, Normalized Modal Difference (NMD) is used to calculate the multiplication matrix using the analytical DOFs corresponding to the measured DOFs. This matrix is then used to expand the measured mode shape to unmeasured DOFs. A simulated simply supported beam is used to demonstrate the performance of the methods. These methods are then compared with two most promising existing methods, namely the Kidder dynamic expansion and the modal expansion methods. It is observed that the performance of the modal flexibility method is comparable with existing methods. NMD also have the potential to expand the mode shapes though it is seen to be more sensitive to the distribution of error between finite element method and actual test data.

Design and Simulation of Silicon-Based Ultrasonic Nozzles for Production of Monodispersed Droplets

2007 ◽  
Author(s):  
C. H. Cheng ◽  
N. Wang ◽  
Y. L. Song ◽  
S. C. Tsai ◽  
Y. F. Chou ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Mode Shape ◽  
High Frequency ◽  
Vibration Amplitude ◽  
Vibration Mode ◽  
Longitudinal Vibration ◽  
Ultrasonic Frequency ◽  
Resonant Frequencies ◽  
Silicon Based ◽  
Good Agreement

This paper reports the design and simulation of Si-based ultrasonic nozzles (or atomizers) that consist of multiple Fourier horns at ultrasonic frequency ranging from 0.57 to 2.75 MHz. Such high frequency ultrasonic nozzles should produce monodispersed droplets (or drops) 2 to 6 μm in diameter, which are ideal to efficiently target medications to different locations within the respiratory system depending on the site of disease. 3-D simulations on vibration mode shape and impedance of the nozzles using a commercial finite element method (FEM) program, ANSYS, yield resonant frequencies of pure longitudinal vibration in good agreement with the measured values. The mode shape simulation also shows that at the resonant frequency the longitudinal vibration amplitude gain at the nozzle tip for 3-horn nozzle is 8, four times that for a single-horn nozzle.

High Sensitivity Damage Detection With Vibration Mode Shape Tuning Through the Optimal Design of Piezoelectric Actuators

2015 ◽  
Author(s):  
Shengjie Zhao ◽  
Nan Wu ◽  
Yukun Cheng
Keyword(s):  
Optimal Design ◽  
Damage Detection ◽  
Numerical Simulations ◽  
Mode Shape ◽  
Vibration Mode ◽  
Piezoelectric Actuators ◽  
High Sensitivity ◽  
Detection Sensitivity ◽  
Mode Shapes ◽  
Shape Tuning

This paper develops an advanced technique to significantly increase the frequency based damage detection sensitivity on a beam structure through a mode shape tuning process with the optimal design of the piezoelectric actuators. Piezoelectric sensors and actuators are mounted on the surface of the host beams to generate the feedback voltage and the active controlled excitations respectively. The excitations induced by the piezoelectric effect will be utilized to change the curvature distribution of the vibration mode shapes of the host beam structure so as to magnify the natural frequency difference between the intact beam and the damaged one to realize the high sensitivity damage detection. In this paper, theoretical models of the cantilever beams with and without mode shape tuning induced by piezoelectric layers are built first, while the damage is represented by a fixed end crack. Then, through the numerical simulations, the vibration mode shapes and corresponding natural frequencies of the beams can be solved to study the sensitivity improvement by using the proposed technique. In order to improve the detection efficiency, a couple of piezoelectric actuators are installed symmetrically on the upper and lower surface of the host beam, generating shifty bending moments to tune the vibration mode shapes. The actuation voltages applied on the actuators are determined by applying certain gain to the voltage from the piezoelectric sensors. Different gain factors are applied to the mode shape tuning process to reveal their effects on damage detection sensitivity improvement. As a result of the control process with proper gain factor, the curvature is more concentrated at the position close to the crack in the first vibration mode shape of the damaged beam comparing with the one without mode shape tuning. Therefore, the first natural frequency variation induced by the crack effect with mode shape tuning is much more significant than the one without mode shape tuning. In addition, further numerical simulations also indicate that the improvement of the detection sensitivity is closely related to the dimensions of the piezoelectric actuators. To realize better detection results, the optimal design of the size of the piezoelectric actuators is presented. The optimal length of the piezoelectric actuators is found leading to the best performance on damage detection. The theoretical studies and numerical simulations reflect that the proposed technique with mode shape tuning and optimally designed actuators is effective and promising in the field of damage detection. It is noted that the proposed technique can also be applied to improve the sensitivity of frequency based damage detection on other structures, e.g. plates and frames.

Tire Vibrations

1977 ◽  
Vol 5 (4) ◽  
pp. 202-225 ◽  
Author(s):  
G. R. Potts ◽  
C. A. Bell ◽  
L. T. Charek ◽  
T. K. Roy
Keyword(s):  
Natural Frequencies ◽  
Standing Waves ◽  
Resonant Mode ◽  
Mode Shapes ◽  
Resonant Vibrations ◽  
Resonant Frequencies ◽  
Radial Tire ◽  
Analysis Techniques ◽  
Thin Ring ◽  
Good Agreement

Abstract Natural frequencies and vibrating motions are determined in terms of the material and geometric properties of a radial tire modeled as a thin ring on an elastic foundation. Experimental checks of resonant frequencies show good agreement. Forced vibration solutions obtained are shown to consist of a superposition of resonant vibrations, each rotating around the tire at a rate depending on the mode number and the tire rotational speed. Theoretical rolling speeds that are upper bounds at which standing waves occur are determined and checked experimentally. Digital Fourier transform, transfer function, and modal analysis techniques used to determine the resonant mode shapes of a radial tire reveal that antiresonances are the primary transmitters of vibration to the tire axle.

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

scholarly journals Mode Shape-Based Damage Detection Method (MSDI): Experimental Validation

2021 ◽  
Vol 11 (10) ◽  
pp. 4589
Author(s):  
Ivan Duvnjak ◽  
Domagoj Damjanović ◽  
Marko Bartolac ◽  
Ana Skender
Keyword(s):  
Boundary Conditions ◽  
Damage Detection ◽  
Mode Shape ◽  
Experimental Validation ◽  
Detection Method ◽  
Dynamic Properties ◽  
Damage Index ◽  
Main Principle ◽  
The Difference ◽  
Different Levels

The main principle of vibration-based damage detection in structures is to interpret the changes in dynamic properties of the structure as indicators of damage. In this study, the mode shape damage index (MSDI) method was used to identify discrete damages in plate-like structures. This damage index is based on the difference between modified modal displacements in the undamaged and damaged state of the structure. In order to assess the advantages and limitations of the proposed algorithm, we performed experimental modal analysis on a reinforced concrete (RC) plate under 10 different damage cases. The MSDI values were calculated through considering single and/or multiple damage locations, different levels of damage, and boundary conditions. The experimental results confirmed that the MSDI method can be used to detect the existence of damage, identify single and/or multiple damage locations, and estimate damage severity in the case of single discrete damage.

scholarly journals Impact of Geometrical Imperfections on Estimation of Buckling and Limit Loads in a Silo Segment Using the Vibration Correlation Technique

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 567
Author(s):  
Łukasz Żmuda-Trzebiatowski ◽  
Piotr Iwicki
Keyword(s):  
Natural Frequencies ◽  
Vibration Mode ◽  
Mode Shapes ◽  
Correlation Technique ◽  
Limit Loads ◽  
Linear Buckling ◽  
Geometrical Imperfections ◽  
Linear Problems ◽  
Formed Channel ◽  
Corrugated Wall

The paper examines effectiveness of the vibration correlation technique which allows determining the buckling or limit loads by means of measured natural frequencies of structures. A steel silo segment with a corrugated wall, stiffened with cold-formed channel section columns was analysed. The investigations included numerical analyses of: linear buckling, dynamic eigenvalue and geometrically static non-linear problems. Both perfect and imperfect geometries were considered. Initial geometrical imperfections included first and second buckling and vibration mode shapes with three amplitudes. The vibration correlation technique proved to be useful in estimating limit or buckling loads. It was very efficient in the case of small and medium imperfection magnitudes. The significant deviations between the predicted and calculated buckling and limit loads occurred when large imperfections were considered.

Investigating the vibrational behaviour of a rotating two-blade propeller by using a self-tracking method

2018 ◽  
Vol 233 (3) ◽  
pp. 835-847 ◽  
Author(s):  
Mohammad-Reza Ashory ◽  
Farhad Talebi ◽  
Heydar R Ghadikolaei ◽  
Morad Karimpour
Keyword(s):  
Natural Frequency ◽  
Measurement Errors ◽  
Mode Shapes ◽  
Model Parameters ◽  
Test Results ◽  
Modal Assurance Criterion ◽  
Tracking Method ◽  
Strong Resemblance ◽  
Test Scenarios ◽  
Good Agreement

This study investigated the vibrational behaviour of a rotating two-blade propeller at different rotational speeds by using self-tracking laser Doppler vibrometry. Given that a self-tracking method necessitates the accurate adjustment of test setups to reduce measurement errors, a test table with sufficient rigidity was designed and built to enable the adjustment and repair of test components. The results of the self-tracking test on the rotating propeller indicated an increase in natural frequency and a decrease in the amplitude of normalized mode shapes as rotational speed increases. To assess the test results, a numerical model created in ABAQUS was used. The model parameters were tuned in such a way that the natural frequency and associated mode shapes were in good agreement with those derived using a hammer test on a stationary propeller. The mode shapes obtained from the hammer test and the numerical (ABAQUS) modelling were compared using the modal assurance criterion. The examination indicated a strong resemblance between the hammer test results and the numerical findings. Hence, the model can be employed to determine the other mechanical properties of two-blade propellers in test scenarios.

Identifying VIV Vibration Modes by Use of the Empirical Orthogonal Functions Technique

2002 ◽  
Author(s):  
Gudmund Kleiven
Keyword(s):  
Model Test ◽  
Vibration Mode ◽  
Multivariate Data ◽  
Empirical Orthogonal Functions ◽  
Mode Shapes ◽  
Data Sets ◽  
Vibration Modes ◽  
Ocean Engineering ◽  
Orthogonal Functions ◽  
Related Technique

The Empirical Orthogonal Functions (EOF) technique has widely being used by oceanographers and meteorologists, while the Singular Value Decomposition (SVD being a related technique is frequently used in the statistics community. Another related technique called Principal Component Analysis (PCA) is observed being used for instance in pattern recognition. The predominant applications of these techniques are data compression of multivariate data sets which also facilitates subsequent statistical analysis of such data sets. Within Ocean Engineering the EOF technique is not yet widely in use, although there are several areas where multivariate data sets occur and where the EOF technique could represent a supplementary analysis technique. Examples are oceanographic data, in particular current data. Furthermore data sets of model- or full-scale data of loads and responses of slender bodies, such as pipelines and risers are relevant examples. One attractive property of the EOF technique is that it does not require any a priori information on the physical system by which the data is generated. In the present paper a description of the EOF technique is given. Thereafter an example on use of the EOF technique is presented. The example is analysis of response data from a model test of a pipeline in a long free span exposed to current. The model test program was carried out in order to identify the occurrence of multi-mode vibrations and vibration mode amplitudes. In the present example the EOF technique demonstrates the capability of identifying predominant vibration modes of inline as well as cross-flow vibrations. Vibration mode shapes together with mode amplitudes and frequencies are also estimated. Although the present example is not sufficient for concluding on the applicability of the EOF technique on a general basis, the results of the present example demonstrate some of the potential of the technique.

Fluid Added Mass Effect in the Modal Response of a Pump-Turbine Impeller

2009 ◽  
Author(s):  
Eduard Egusquiza ◽  
Carme Valero ◽  
Quanwei Liang ◽  
Miguel Coussirat ◽  
Ulrich Seidel
Keyword(s):  
Natural Frequencies ◽  
Experimental Tests ◽  
Mass Effect ◽  
Added Mass ◽  
Mode Shapes ◽  
Pump Turbine ◽  
Modal Response ◽  
Surrounding Fluid ◽  
Turbine Impeller ◽  
Good Agreement

In this paper, the reduction in the natural frequencies of a pump-turbine impeller prototype when submerged in water has been investigated. The impeller, with a diameter of 2.870m belongs to a pump-turbine unit with a power of around 100MW. To analyze the influence of the added mass, both experimental tests and numerical simulations have been carried out. The experiment has been performed in air and in water. From the frequency response functions the modal characteristics such as natural frequencies and mode shapes have been obtained. A numerical simulation using FEM (Finite Elements Model) was done using the same boundary conditions as in the experiment (impeller in air and surrounded by a mass of water). The modal behaviour has also been calculated. The numerical results were compared with the available experimental results. The comparison shows a good agreement in the natural frequency values both in air and in water. The reduction in frequency due to the added mass effect of surrounding fluid has been calculated. The physics of this phenomenon due to the fluid structure interaction has been investigated from the analysis of the mode-shapes.

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