Analysis of Granular Damping Using Hilbert Transform Based Technique

2007 ◽  
Author(s):  
X. Fang ◽  
H. Luo ◽  
J. Tang
Keyword(s):  
Hilbert Transform ◽  
Damping Ratio ◽  
Temporal Frequency ◽  
Nonlinear Damping ◽  
Vibration Level ◽  
Damping Characteristics ◽  
The Difference ◽  
The Hilbert Transform ◽  
Granular Damping ◽  
The Impact

Granular damping results from a combination of energy dissipation mechanisms including the impact and the friction between the vibrating structure and granules and among the granules. Although simple in concept, granular damping is very complicated and its performance depends on a number of factors, such as vibration level, granular material properties, and packing ratio, etc. In this study, free vibration tests are conducted on a cantilevered beam incorporated with granular damping. A signal analysis approach based on the Hilbert transform (HT) is then employed to identify the nonlinear damping characteristics from the acquired responses, such as the dependency of the natural frequency and damping ratio on vibration level. This HT based analysis can produce an accurate temporal-frequency amplitude/energy analysis which provides us with physical insights of the nonlinear transient response. A direct comparison between the granular damping and the impact damping (with single impactor to dissipate vibratory energy) is performed to highlight the difference between these two as well as the advantages of granular damping. Finally, validity of the proposed approach is also examined by the successful prediction of vibration response using the extracted granular damping characteristics.

Investigation of Granular Damping in Transient Vibrations Using Hilbert Transform Based Technique

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
X. Fang ◽  
H. Luo ◽  
J. Tang
Keyword(s):  
Hilbert Transform ◽  
Damping Ratio ◽  
Temporal Frequency ◽  
Nonlinear Damping ◽  
Vibration Level ◽  
Damping Characteristics ◽  
The Difference ◽  
The Hilbert Transform ◽  
Granular Damping ◽  
The Impact

Granular damping results from a combination of energy dissipation mechanisms including the impact and the friction between the vibrating structure and granules and among the granules. Although simple in concept, granular damping is very complicated and its performance depends on a number of factors, such as vibration level, granular material properties, packing ratio, etc. In this study, free vibration experiments are conducted on a cantilevered beam incorporated with granular damping. A signal analysis approach based on the Hilbert transform (HT) is then employed to identify the nonlinear damping characteristics from the acquired responses, such as the dependency of the natural frequency and damping ratio on the vibration level. This HT based analysis can produce an effective temporal-frequency amplitude∕energy analysis, which provides us with physical insights of the nonlinear transient response. A direct comparison between the granular damping and the impact damping (with single impactor to dissipate vibratory energy) is performed to highlight the difference between these two and the advantages of granular damping. Finally, the validity of the proposed approach is also examined by the successful prediction of vibration response using the extracted granular damping characteristics.

scholarly journals Investigation on Damping Characteristics of Hydrostatic Bearing Film by Using Scale Method

2021 ◽  
Author(s):  
Sheng-Yen Hu ◽  
Wen-Chou Chen ◽  
Chien-Hsun Wang ◽  
Hsin-Ming Fu ◽  
Yuan Kang
Keyword(s):  
Damping Ratio ◽  
Resonant Peak ◽  
Test Results ◽  
Scaling Method ◽  
Single Degree Of Freedom ◽  
Hydrostatic Bearing ◽  
Damping Characteristics ◽  
Mass Spring ◽  
The Impact

Abstract The resonant peaks can be suppressed by damping, those effects is dependent on damping ratio of system. In this paper, we propose a scaling method to evaluate the damping ratio of hydrostatic bearings for the data from model test. This method fits specifically for the overdamping of all hydrostatic bearing. This is direct and the easiest method to obtain the damping characteristics of oil film for the lowest band before the first resonant peak. The frequency responses of acceleration per force for a single-degree-of-freedom mass-spring-damper model is used to generate the evaluation scales for the damping ratios of the modal test results of worktable mounting on hydrostatic bearing. The case study for experimental results of the impact response are evaluated for damping ratio of the hydrostatic film by these method. Furthermore, using this scaling method, the influences of three types of compensations on the damping ratio of a hydrostatic bearing are compared. The results reveal that the constant flow has the largest damping ratio, and the capillary restrictor has the smallest one.

scholarly journals Improved Method for the Quantification of Motility in Glia and Other Morphologically Complex Cells

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Mari Sild ◽  
Robert P. Chatelain ◽  
Edward S. Ruthazer
Keyword(s):  
Radial Glia ◽  
Temporal Frequency ◽  
Power Spectra ◽  
Motility Index ◽  
Complex Cells ◽  
Graphical Interfaces ◽  
The Difference ◽  
Imaging Artifact ◽  
Difference Images ◽  
The Impact

Cells such as astrocytes and radial glia with many densely ramified, fine processes pose particular challenges for the quantification of structural motility. Here we report the development of a method to calculate a motility index for individual cells with complex, dynamic morphologies. This motility index relies on boxcar averaging of the difference images generated by subtraction of images collected at consecutive time points. An image preprocessing step involving 2D projection, edge detection, and dilation of the raw images is first applied in order to binarize the images. The boxcar averaging of difference images diminishes the impact of artifactual pixel fluctuations while accentuating the group-wise changes in pixel values which are more likely to represent real biological movement. Importantly, this provides a value that correlates with mean process elongation and retraction rates without requiring detailed reconstructions of very complex cells. We also demonstrate that additional increases in the sensitivity of the method can be obtained by denoising images using the temporal frequency power spectra, based on the fact that rapid intensity fluctuations over time are mainly due to imaging artifact. The MATLAB programs implementing these motility analysis methods, complete with user-friendly graphical interfaces, have been made publicly available for download.

scholarly journals Displacement Transmissibility Characteristics of Harmonically Base Excited Damper Isolators with Mixed Viscous Damping

2013 ◽  
Vol 20 (5) ◽  
pp. 921-931 ◽  
Author(s):  
Xiaojuan Sun ◽  
Jianrun Zhang
Keyword(s):  
Damping Ratio ◽  
Harmonic Balance Method ◽  
Nonlinear Damping ◽  
Viscous Damping ◽  
Damping Force ◽  
Response Characteristics ◽  
Damping Characteristics ◽  
Linear Damping ◽  
Frequency Ratios ◽  
Good Agreement

The viscous damping force in the mixed form asfd(x˙)=c1x˙+c2|x˙|x˙can well describe damping characteristics of isolators and dampers in many cases. In this paper, performance characteristics of single-degree-of-freedom (SDOF) linear-stiffness isolators with mixed and piecewise mixed viscous damping are analytically examined under harmonic base excitation. Based on the first-order harmonic balance method (HBM), both relative and absolute displacement transmissibility expressions with the equivalent linear damping coefficient (ELDC) are given. And the analytical calculations show good agreement with the numerical results. Also, the influence of nonlinear damping on the response characteristics is investigated by comparing the transmissibility of linear and nonlinear systems. The resonant frequency always shifts to a lower value as the nonlinear damping component of the forcefd(x˙)=c1x˙+c2|x˙|x˙becomes stronger, and when the damping ratio in the corresponding linear model is relatively high, the relative transmissibility decreases at frequencies higher than the resonance frequency of the corresponding linear damping system and the absolute one increases for the frequency ratios above2. Finally, the displacement transmissibility of a nonlinear isolator with piecewise mixed viscous damping is discussed and the process shows research similarity with the non-piecewise case.

scholarly journals Statistical t-test assessment on performance of power system stabilizer for oscillation damping

2021 ◽  
Vol 10 (3) ◽  
pp. 271
Author(s):  
Wai Myat Thu ◽  
Kyaw Myo Lin
Keyword(s):  
Power System ◽  
Damping Ratio ◽  
Test System ◽  
T Test ◽  
Statistical Process ◽  
Test Analysis ◽  
The Difference ◽  
System Stabilizer ◽  
Oscillation Damping ◽  
The Impact

The statistical operation is necessary to validate the analytical procedure since the most important common operation is the comparison of result data to quantify accuracy and precision. In this paper, a statistical process is proposed to ensure the impact of power system stabilizers (PSSs) in 202-bus, 40-machine MEPE test system. The eigenvalue analysis is utilized for detecting the lowest damping modes and evaluating the damping ratio of system oscillation, and these modes are applied as input for statistical analysis. A t-test analysis was performed on the difference of damping performance by proposed designed PSS, tuned PSS, and without PSS to support the hypothesis. The t-test results validated that the MEPE test system with designed PSS is most applicable for the improvement of oscillation damping in the power system.

Experimental damping ratio evaluation using Hilbert transform in filament-wound composite plates

2021 ◽  
pp. 096739112110020
Author(s):  
Enzo Costamilan ◽  
Alexandre Marks Löw ◽  
Marcos Daniel de Freitas Awruch ◽  
Sandro C Amico ◽  
Herbert Martins Gomes
Keyword(s):  
Hilbert Transform ◽  
Damping Ratio ◽  
Composite Plates ◽  
Vibration Signal ◽  
Element Model ◽  
Filament Winding ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Filament Wound Composite ◽  
The Hilbert Transform

The aim of this work is the evaluation of damping ratio in composite materials with orthogonal fiber orientation based on experimental and numerical techniques. In this study, the logarithmic decrement and the envelope techniques calculated using Hilbert transform are used. Carbon fiber/epoxy composites manufactured by filament winding are dynamically tested in free vibration. Post-processing and data analysis are performed with the developed codes. These comprise the use of a band-pass filter to isolate the first fundamental frequency from the other modes of vibration and noise present in the acquired signal. Then, the Hilbert transform is used to estimate the envelope of the vibration signal and the exponential curve is adjusted to obtain the envelope, in order to evaluate the structural damping ratio. Comparisons with a fitted finite element model are used for validation. The results revealed that damping varied proportionally with the number of layers, the ply orientation and, less evidently, with the length of the samples.

The Effect of Longitudinal Center of Gravity Position on the Sway Stability of a Small Cargo Trailer

2008 ◽  
Author(s):  
Michael G. Gilbert ◽  
Daniel A. Godrick ◽  
Richard H. Klein
Keyword(s):  
Dynamic Response ◽  
Damping Ratio ◽  
Leaf Spring ◽  
Loading Conditions ◽  
Novice Drivers ◽  
Training Requirements ◽  
Mandatory Training ◽  
Damping Characteristics ◽  
The Stability ◽  
The Impact

Small and mid-sized cargo trailers are often used to transport goods by people with limited experience in loading trailers and driving vehicles with trailers attached. This paper examines the effect of front to rear load position on the stability of a trailer by measuring its dynamic response to a variety of steer inputs at several different highway speeds. Additionally, tests with varying steers and speeds were performed with a simulated suspension malfunction to study the trailer’s dynamic response to this condition. Trailer sway has been a well-documented trailer characteristic for decades. However there are no special driver’s licensing or mandatory training requirements for even large trailers and campers. The trailer chosen for this test was a lightweight double axle cargo trailer commonly rented by people with limited to no towing experience. This consumer is likely to be unfamiliar with the best practices of trailer loading. This consumer is also likely a non-professional driver with little to no towing experience in the event of encountering unexpected trailer sway. Therefore it was the goal of the authors to determine how the stability of this type of trailer varies with different front to rear loading conditions and speeds to see if it is safe to operate on the highways by novice drivers. Trailer sway stability was determined by measuring the trailer sway (articulation) response during repeated, pulse steer tests. The trailer sway damping characteristics were measured, as a “damping ratio”, for six different hitch loads that corresponded to six different longitudinal loading conditions. These conditions, expressed as % load forward of the trailer centerline / % load aft of the trailer centerline were: 65/35, 60/40, 55/45, 50/50, 45/55, and 40/60. These loading conditions were tested per SAE J2664 [1] protocol. The resulting trailer sway characteristics for each loading condition then were compared to published trailer sway stability criteria [2, 3] to determine the suitability of this particular tow vehicle-trailer combination for use by the public in a rental market. The impact of a suspension malfunction on the trailer stability was also studied. This consisted of a detachment of one rear leaf spring hanger.

The Simulation Research of Damping Characteristics for the Underwater Vehicle Moving under or Exceeding Water

2013 ◽  
Vol 432 ◽  
pp. 281-287
Author(s):  
Chun Fang Zhang ◽  
Jing Bo Gao ◽  
Hai Bo Lü ◽  
Zhen Jun Zhao ◽  
Cong Wang
Keyword(s):  
Numerical Simulation ◽  
Damping Ratio ◽  
Continuous Process ◽  
Underwater Vehicle ◽  
Water Model ◽  
Simulation Research ◽  
Fluid Structure ◽  
Damping Characteristics ◽  
The Impact ◽  
Water Exit

The vehicle may vibrate when it moves under or exceeding water. This vibration will interact with the flow filed around to form a fluid-structure interactiondynamics system. In this paper, the numerical simulation of a cylinder in the process of moving under or exceeding water with ABAQUS and FLUENT is presented. Simultaneously, the first three damping ratio of the system are obtained by damping identification. For different density, viscosity and velocity of water, model separately to get the impact of each factor. Besides, the continuous process of exceeding water has been discretized to obtaindifferent oscillating curvesat different positions with respect to the water,and then the change of the damping ratio is presented. Thus the damping characteristics of the system in the water-exit process have been obtained approximately.

Evaluation of the impact of public investment programs on social and economic performance of territories

2019 ◽  
pp. 109-123
Author(s):  
I. E. Limonov ◽  
M. V. Nesena
Keyword(s):  
Bayesian Modeling ◽  
Positive Impact ◽  
Public Investment ◽  
Difference In Differences ◽  
The Public ◽  
Export Activity ◽  
Regional Investment ◽  
The Difference ◽  
The Impact ◽  
Development Institution

The purpose of this study is to evaluate the impact of public investment programs on the socio-economic development of territories. As a case, the federal target programs for the development of regions and investment programs of the financial development institution — Vnesheconombank, designed to solve the problems of regional development are considered. The impact of the public interventions were evaluated by the “difference in differences” method using Bayesian modeling. The results of the evaluation suggest the positive impact of federal target programs on the total factor productivity of regions and on innovation; and that regional investment programs of Vnesheconombank are improving the export activity. All of the investments considered are likely to have contributed to the reduction of unemployment, but their implementation has been accompanied by an increase in social inequality.

Model of multicomponent narrow-band periodical non-stationary random signal

2020 ◽  
Vol 2020 (48) ◽  
pp. 17-24
Author(s):  
I.M. Javorskyj ◽  
◽  
R.M. Yuzefovych ◽  
P.R. Kurapov ◽  
◽  
...  
Keyword(s):  
Time Series ◽  
Real Time ◽  
Hilbert Transform ◽  
Spectral Properties ◽  
Narrow Band ◽  
Analytic Signal ◽  
Random Signal ◽  
Hilbert Transformation ◽  
The Hilbert Transform

The correlation and spectral properties of a multicomponent narrowband periodical non-stationary random signal (PNRS) and its Hilbert transformation are considered. It is shown that multicomponent narrowband PNRS differ from the monocomponent signal. This difference is caused by correlation of the quadratures for the different carrier harmonics. Such features of the analytic signal must be taken into account when we use the Hilbert transform for the analysis of real time series.

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