scholarly journals Measurements of the Hydrodynamic and Vibrational Characteristics to Validate Numerical Calculations of the Structure Excitation by Fluid Flow

2019 ◽  
Vol 10 (3) ◽  
pp. 223-232 ◽  
Author(s):  
A. V. Budnikov ◽  
E. I. Shmelev ◽  
D. A. Kulikov ◽  
A. V. Loginov ◽  
S. M. Dmitriev ◽  
...  
Keyword(s):  
Rupture Life ◽  
Measurement Techniques ◽  
Excitation Frequency ◽  
Hydrodynamic Forces ◽  
Test Model ◽  
Frequency Calculation ◽  
Vibrational Characteristics ◽  
Structure Vibration ◽  
Synchronization Effect ◽  
Vibration Parameters

Structure vibration under the influence of unsteady hydrodynamic forces caused by the flow around their surfaces can adversely affect durability and rupture life. Reducing the adverse effects of hydrodynamic forces is currently possible with the help of linked CFD and vibration calculations. However, for an adequate description of the associated processes one should use calculation models and approaches specific to the hydro-vibration problem. To justify and validate such approaches, an experimental model was developed and a series of structure excitation tests in water flow was carried out.The model comprises two cylinders installed sequentially in water crossflow. Vibration levels, pressure and velocity fluctuations were measured in the tests as a functions of the flow velocity. The application of different non-intrusive measurement techniques was possible due to relatively simple test model construction which may be used for cross-validation and experimental uncertainty quantification.Flow-structure interaction, caused by synchronization effect of the flow separation frequency (or it’s spectral components) and eigenfrequency of cylinder, was analyzed based on simultaneously measured data. The tests performed gave the information about dynamical characteristics of the flow and vibration parameters of cantilevered cylinders. The experimental results are used for identification of required accuracy of hydrodynamic forces calculation by CFD and validation of oneand two-way linked methods for flow excitation frequency calculation.

Calculating Cutoff Speeds of a Multistage Pump Rotor Taking into Account Lomakin Effect in the Front Seal of the Impeller

2020 ◽  
pp. 59-67
Author(s):  
D.G. Svoboda ◽  
A.A. Zharkovskii ◽  
E.A. Ivanov ◽  
I.O. Borshchev
Keyword(s):  
Hydrodynamic Forces ◽  
Centrifugal Pumps ◽  
Pump Rotor ◽  
Operating Modes ◽  
Flow Parameters ◽  
Ansys Cfx ◽  
Vibrational Characteristics ◽  
Shaft Deflection ◽  
Multistage Pump ◽  
Quantitative Impact

Studies of dynamic frequencies are an important stage in designing multistage vane pumps. This research aimed to confirm the rigidity and vibrational reliability of the pump rotor. Based on the recommendations of J.F. Gülich, the nominal rotational speed of the rotor shaft should differ from the cutoff speed by no less than 25 %. The Lomakin effect supposes taking into consideration the hydrodynamic forces acting in the gap seals and having a damping effect on the pump rotor. This research solved the problem of developing and verifying a numerical method of calculating hydrodynamic forces, which arise in seals of vane pumps at critical speeds. The studies were conducted on a ‘dry’ model of the rotor using ANSYS Mechanical software package. During computational modeling of bearings and seals, the COMBIT214 ele¬ment was used where the stiffness coefficient values were set. These values were determined by calculating the flow parameters in the gap seal using ANSYS CFX. The proposed method was verified using the experimental data obtained. The seal rigidity was calculated for different operating modes of the pump. It was shown that the hydrodynamic forces which arose in the gap seals had a significant influence on the rotor’s critical speed. Accounting for these forces increased the main own frequency of the rotor by approximately 44 %. This fact had a significant qualitative and quantitative impact on the vibrational characteristics of the pump. This study showed that the value of the hydrodynamic force was influenced by several factors: shaft deflection, differential pressure and geometry of the gap seal. The proposed method is recommended for use for multistage centrifugal pumps.

Acoustoelastic-Based Stress Measurement Utilizing Low-Frequency Flexural Waves

2017 ◽  
Author(s):  
Mohammad I. Albakri ◽  
Vijaya V. N. Sriram Malladi ◽  
Pablo A. Tarazaga
Keyword(s):  
Stress Measurement ◽  
Measurement Techniques ◽  
Excitation Frequency ◽  
Low Frequency ◽  
Lower Sensitivity ◽  
Flexural Waves ◽  
Dispersive Waves ◽  
High Frequencies ◽  
Geometric Uncertainties ◽  
The Cost

Current acoustoelastic-based stress measurement techniques operate at the high-frequency, weakly-dispersive portions of the dispersion curves. The weak dispersive effects at such high frequencies allow the utilization of time-of-flight measurements to quantify the effects of stress on wave speed. However, this comes at the cost of lower sensitivity to the state-of-stress of the structure, and hence calibration at a known stress state is required to compensate for material and geometric uncertainties in the structure under test. In this work, the strongly-dispersive, highly stress-sensitive, low-frequency flexural waves are utilized for stress measurement in structural components. A new model-based technique is developed for this purpose, where the acoustoelastic theory is integrated into a numerical optimization algorithm to analyze dispersive waves propagating along the structure under test. The developed technique is found to be robust against material and geometric uncertainties. In the absence of calibration experiments, the robustness of this technique is inversely proportional to the excitation frequency. The capabilities of the developed technique are experimentally demonstrated on a long rectangular beam, where reference-free, un-calibrated stress measurements are successfully conducted.

scholarly journals Experimental Research on 2 : 1 Parametric Vibration of Stay Cable Model under Support Excitation

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Li-Na Zhang ◽  
Feng-Chen Li ◽  
Xiang Yu ◽  
Peng-Fei Cui ◽  
Xiao-Yong Wang
Keyword(s):  
Numerical Simulation ◽  
Experimental Research ◽  
Excitation Frequency ◽  
Parametric Vibration ◽  
Vibration Test ◽  
Test Model ◽  
Stay Cable ◽  
Test Analysis ◽  
Support Excitation ◽  
Bridge Bearing

For 2 : 1 parametric vibration problem of stay cable under support excitation, a sliding support only in the vertical moving is designed to simulate the bridge stay cable’s vibration test model. Meanwhile, using numerical simulation of cable free vibration and dynamic characteristic test analysis, the experimental research under various conditions is implemented in the actual cable-stayed bridge as the research object, which is compared with the corresponding numerical simulation results. According to the analysis results, it shows that as the vibration test model has 2 : 1 parametric vibration under the support excitation the results of maximum cable displacement from experimental analysis and numerical simulation are basically consistent which revealed that the parametric vibration of stay cable exists and is easy to occur. Additionally, when the bridge bearing excitation frequency is similar to the 2 : 1 frequency ratio, small excitation can indeed lead to the sharp “beat” vibration of cable; therefore it is very necessary to limit the amplitude of support excitation to prevent the occurrence of a large main parametric resonance.

Research on Vibration Transmissibility of Damping Sandwich Arch Profile

2012 ◽  
Vol 248 ◽  
pp. 147-152
Author(s):  
Fei Han ◽  
Min Qing Wang ◽  
Jin Tao Gu
Keyword(s):  
Shell Structure ◽  
Energy Analysis ◽  
Vibration Response ◽  
Test Model ◽  
Analysis Method ◽  
Mechanical Noise ◽  
Important Approach ◽  
Vibration Transmissibility ◽  
Structure Vibration ◽  
Vibration Performance

For coupled plate-shell structure, restraining the vibration transmitted from plate to shell is an important approach to reduce the mechanical noise from the shell. In this paper, a damping sandwich arch profile with rubber as the material of the damping layer is presented and manufactured. Structure vibration response with arch profile applied to the coupled plate-shell test model is measured. And then Statistics Energy Analysis method is used to analyze the effects of major parameters on anti-vibration performance of the arch profile. Research indicates that using damping sandwich arch profile can restrain the vibration response of the shell effectively.

Accelerated Vibration Reliability Testing of Electronic Assemblies Using Sine Dwell With Resonance Tracking

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Quang T. Su ◽  
Mohammad A. Gharaibeh ◽  
Aaron J. Stewart ◽  
James M. Pitarresi ◽  
Martin K. Anselm
Keyword(s):  
Resonant Frequency ◽  
Measurement Techniques ◽  
Excitation Frequency ◽  
Building Blocks ◽  
Test Method ◽  
Circuit Board ◽  
Vibration Measurement ◽  
Fe Model ◽  
Reliability Testing ◽  
Sinusoidal Vibration

In this work, a sinusoidal vibration test method with resonance tracking is employed for reliability testing of circuit assemblies. The system continuously monitors for changes in the resonant frequency of the circuit board and adjusts the excitation frequency to match the resonant frequency. The test setup includes an electrodynamic shaker with a real-time vibration control, resistance monitoring for identifying electrical failures of interconnects, and vibration logging for monitoring changes in the dynamic response of the assembly over time. Reliability tests were performed using the resonance tracking sinusoidal test method for assemblies, each consisting of a centrally mounted ball grid array (BGA) device assembled with 63Sn37Pb and SAC105 solder alloys. These tests show that the resonance tracking method gives more consistent failure times. Failure analysis for the tested devices shows the primary failure mode is “input” trace crack first, followed by fatigue through the solder for complete failure. A finite element (FE) model, correlated with experimental modal analysis, is shown to accurately estimate the circuit board deflection estimated from the harmonic vibration data. This provides a means of estimating the stresses in the electronic interconnections while accounting for the variability between test parts. These fine-tuned vibration measurement techniques and related FE models provide the building blocks for high cycle solder fatigue plots (i.e., S–N curves).

A New Test Bench for Friction Measurements and the Evolution of the Lugre Model to the Frozen Model

2009 ◽  
Author(s):  
J. L. Dion ◽  
G. Chevallier ◽  
O. Penas ◽  
N. Peyret
Keyword(s):  
Test Bench ◽  
Large Range ◽  
Measurement Techniques ◽  
Excitation Frequency ◽  
Parametric Identification ◽  
Lugre Model ◽  
Friction Forces ◽  
Dynamic Excitation ◽  
Accuracy Of Measurements ◽  
Friction Measurements

After a description of existing experimental methods and models built on the dynamic behavior of friction forces between two solids, this paper presents an original new test bench and specific measurement techniques used to better define the accuracy of measurements. This test bench has been designed for a large range of tests in terms of static strain, dynamic excitation, frequency and kinds of surfaces. The second part describes the choice of the model which is a development of the Lugre model we have called “Frozen” Model. Methods for parametric identification are proposed and comparisons between experiments and simulations are presented. In the third part a critical analysis is carried out on the test bench and its applications. (This paper is a part of a study on the prediction of vibration level of space launchers - Ariane V program). A parametrical analysis was conducted to lead and conclude a study on the robustness of the chosen model.

scholarly journals Systems of vibration parameters automated control for diagnostics of equipment technical state

2021 ◽  
Vol 332 ◽  
pp. 01013
Author(s):  
Serhiy Horiashchenko ◽  
Oleg Polishchuk ◽  
Marcin Łukasiewicz ◽  
Maciej Matuszewski ◽  
Vladimir Boykov
Keyword(s):  
Excitation Frequency ◽  
The State ◽  
Diagnostic Feature ◽  
Programming Environment ◽  
Light Industry ◽  
Automated Control ◽  
Spatial Direction ◽  
Vibration Sensors ◽  
Operational Information ◽  
Vibration Parameters

The article deals with the issues of the spatial direction of measurement, which is optimal in terms of recognition of the state of a particular unit node and preparation of control points for diagnosis. To form a diagnostic feature, the representation of the signal in a rather narrow range has been used, for instance, in the area of one of the harmonics of the fundamental mechanism excitation frequency. To process such signals, an integrated programming environment developed in the style of Microsoft Visual products has been created. To ensure the requirements of optimal vibration analysis, the structure of stationary equipment control systems has been proposed. Analysis of random vibration of the diagnosed object is done using real-time two-channel analyzers. Each analyzer channel has a processor for fast Fourier transform and operational information. The two available channels can allow assessment of the state of the object by special correlation functions. In contrast to the known methods, the established methods of determining the frequency range of defects of various light industry machine nodes differ in taking account size of parts and equipment nodes, and the possibility to use narrow-band filtering. The analysis of possibilities to install vibration sensors has been carried out.

scholarly journals Electromagnetic Vibration Energy Harvesting for Railway Applications

2018 ◽  
Vol 148 ◽  
pp. 12004 ◽  
Author(s):  
S. Bradai ◽  
S. Naifar ◽  
C. Viehweger ◽  
O. Kanoun
Keyword(s):  
Energy Harvesting ◽  
Excitation Frequency ◽  
Laser Sensor ◽  
Vibration Source ◽  
Efficient Design ◽  
Vibration Energy Harvesting ◽  
Railway Traffic ◽  
Electromagnetic Vibration ◽  
Vibration Parameters ◽  
German Cities

Safe localization of trains via GPS and wireless sensors is essential for railway traffic supervision. Especially for freight trains and because normally no power source is available on the wagons, special solutions for energy supply have to be developed based on energy harvesting techniques. Since vibration is available in this case, it provides an interesting source of energy. Nevertheless, in order to have an efficient design of the harvesting system, the existing vibration needs to be investigated. In this paper, we focus on the characterization of vibration parameters in railway application. We propose an electromagnetic vibration converter especially developed to this application. Vibration profiles from a train traveling between two German cities were measured using a data acquisition system installed on the train’s wagon. Results show that the measured profiles present multiple frequency signals in the range of 10 to 50 Hz and an acceleration of up to 2 g. A prototype for a vibration converter is designed taking into account the real vibration parameters, robustness and integrability requirements. It is based on a moving coil attached to a mechanical spring. For the experimental emulation of the train vibrations, a shaker is used as an external artificial vibration source controlled by a laser sensor in feedback. A maximum voltage of 1.7 V peak to peak which corresponds to a maximum of 10 mW output power where the applied excitation frequency is close to the resonant frequency of the converter which corresponds to 27 Hz.

scholarly journals Environmental dust repelling from hydrophilic/hydrophobic surfaces under sonic excitations

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Abba Abdulhamid Abubakar ◽  
Bekir Sami Yilbas ◽  
Hussain Al-Qahtani ◽  
Ammar Alzaydi
Keyword(s):  
Polyvinyl Chloride ◽  
High Speed ◽  
Excitation Frequency ◽  
Film Surface ◽  
Optical Transmittance ◽  
Dip Coating ◽  
Dust Particles ◽  
Hydrophobic Surfaces ◽  
Vibrational Characteristics ◽  
Chloride Film

Abstract Dust repelling from transparent polyvinyl chloride film surface via sonic excitation is examined and dynamics of repelled (inflight) dust particles are analyzed. An experimental rig is designed and built to assess the vibrational characteristics of the polyvinyl chloride film at different frequencies of sonic excitation. A high speed recording system and tracking program are utilized monitoring and evaluating the dynamics of the inflight particles. The dynamics of inflight particles are also simulated numerically and the predictions are compared with those of the experimental data. In order to examine the influence of dust particle adhesion on the dynamics of the inflight particles, the polyvinyl chloride film surface is hydrophobized through dip coating by functionalized nano-silica particles. Improvement of the optical transmittance of the dust mitigated film is determined via outdoor tests. The findings demonstrate that sonic excitation repels the particles from the film surface and it is more pronounced at 64 Hz excitation frequency while demonstrating that sonic excitation can be used for dust removal from transparent surfaces. The mitigation via sonic excitation improves the optical transmittance of the dusty surface by 77%, which becomes more apparent for hydrophobic surfaces.

scholarly journals The Effect of Plate Discretization on Accuracy of the Sound Radiation Efficiency Measurements

2015 ◽  
Vol 39 (4) ◽  
pp. 511-518 ◽  
Author(s):  
Karolina Kolber ◽  
Anna Snakowska ◽  
Michał Kozupa
Keyword(s):  
Measurement Techniques ◽  
Excitation Frequency ◽  
Low Frequency ◽  
Sound Radiation ◽  
Technical Aspect ◽  
Radiation Efficiency ◽  
Vibration Velocity ◽  
Optimum Level ◽  
Velocity Amplitude ◽  
Sound Radiation Efficiency

Abstract This paper deals with the problem of the effect of discretization level and certain other parameters characterizing the measurement setup on accuracy of the process of determination of the sound radiation efficiency by means of the Discrete Calculation Method (DCM) described by Hashimoto (2001). The idea behind DCM consists in virtual division of an examined sound radiating structure into rectangular elements each of which is further assumed to contribute to the total radiation effect in the same way as a rigid circular piston having the surface area equal to this of the corresponding virtual element and vibrating in an infinite rigid baffle. The advantage of the method over conventional sound radiation efficiency measurement techniques consists in the fact that instead of acoustic pressure values, source (plate) vibration velocity amplitude values are measured in a selected number of regularly distributed points. In many cases, this allows to determine the sound radiation efficiency with sufficient accuracy, especially for the low frequency regime. The key part of the paper is an analysis of the effect of discretization level (i.e. the choice of the number of points at which vibration amplitude measurements are to be taken with the use of accelerometers) on results obtained with the use of the method and their accuracy. The problem of determining an optimum level of discretization for given excitation frequency range is a very important issue as the labor intensity (time-consuming aspect) of the method is one of its main flaws. As far as the technical aspect of the method is concerned, two different geometrical configurations of the measurement setup were tested.

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