scholarly journals Loss Factor of Elastomeric Dampers for Rotating Machinery Application

2018 ◽  
Vol 7 (4.35) ◽  
pp. 107
Author(s):  
Darvind Asokan ◽  
Jawaid I. Inayat Hussain
Keyword(s):  
Loss Factor ◽  
Dominant Role ◽  
Rotating Machinery ◽  
Stationary Condition ◽  
Shaft Rotation ◽  
Elastomeric Dampers ◽  
Half Power ◽  
Work Impact ◽  
Rotating Load ◽  
Good Agreement

Elastomeric dampers have potential application in rotating machinery vibration control. They are however not widely used due to lack of reliable data on their loss factor. Most available data on these dampers are obtained from testing undertaken during stationary condition of the shaft. When the shaft rotates, the dampers are subjected to rotating load that may affect their loss factor. The effect of shaft rotation on the loss factor is experimentally examined in this work. Impact test was used to determine the frequency response function (FRF) of the dampers. For the dampers subjected to rotating load, the loss factor values derived from the FRF was found to be in good agreement with those determined from the half-power bandwidth method. The results further showed that the loss factor at resonant frequency determined from testing of the dampers under stationary shaft condition underestimates the values of the loss factor when the shaft is rotating. The effect of shaft rotation on the values of the damper’s loss factor was more noticeable for the response in the X-direction as opposed to the Y-direction, indicating that pre-strain plays a more dominant role in influencing the loss factor of the dampers compared to the dynamic amplitude.

Research on Damping Properties of TiN Coating Prepared with Arc Ion Plating

2012 ◽  
Vol 184-185 ◽  
pp. 1167-1170
Author(s):  
Guang Yu Du ◽  
Zhen Tan ◽  
Kun Liu ◽  
Hao Chai ◽  
De Chun Ba
Keyword(s):  
Chemical Composition ◽  
Surface Morphology ◽  
Loss Factor ◽  
Steel Substrate ◽  
Damping Ratio ◽  
Energy Dispersive Spectrometer ◽  
Tin Coating ◽  
Arc Ion Plating ◽  
Ion Plating ◽  
Half Power

In this paper TiN coating was prepared on stainless steel substrate using arc ion plating technique. The coating samples’ phases, surface morphology, micro-determination chemical composition, loss factor and damping ratio were tested. The phases of TiN coating were determined by X-ray diffraction (XRD) technique. The surface morphology and chemical composition of the TiN coating were analyzed by scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS), respectively. The damping performance of the samples was measured by hammering activation according half power bandwidth method. The loss factor or damping ratio of samples were obtained according frequency response curve. The results showed that damping performance of samples was considerably improved by TiN coatings.

scholarly journals Low Cross-Polarization Improved-Gain Rectangular Patch Antenna

Electronics ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1189 ◽  
Author(s):  
Anurag Singh ◽  
Sandip Vijay ◽  
Rudra Narayan Baral
Keyword(s):  
Patch Antenna ◽  
Frequency Selective Surface ◽  
Cross Polarization ◽  
Gain Enhancement ◽  
Rectangular Patch ◽  
Shorting Pin ◽  
Half Power ◽  
Broadside Radiation ◽  
Polarization Level ◽  
Good Agreement

In this paper, a low cross-polarization improved-gain rectangular patch antenna is presented. A patch-ground shorting pin with defected patch structure (DPS) is introduced to suppress the cross-polarization level. A High Reflective Frequency Selective Surface (HRFSS) superstrate is designed and placed over the proposed antenna at an optimized position to intensify the gain. To characterize the unit-cell of the superstrate, its transmission characteristics are extracted and discussed. Integration of the superstrate achieves a beam contraction resulting in a gain enhancement to 10.65 dBi. The proposed antenna has perfect broadside radiation with a cross-polarization level of below −30 dB in the entire half power beamwidth. The prototype of the antenna exhibits good agreement between experimental and simulated results.

scholarly journals Contributions of Trans-boundary Transport to the Summertime Air Quality in Beijing, China

2016 ◽  
Author(s):  
Jiarui Wu ◽  
Guohui Li ◽  
Junji Cao ◽  
Naifang Bei ◽  
Yichen Wang ◽  
...  
Keyword(s):  
Air Quality ◽  
Control Strategies ◽  
Dominant Role ◽  
Fine Particulate Matter ◽  
Temporal Variations ◽  
Pollutant Emissions ◽  
Beijing China ◽  
Local Emissions ◽  
Factor Separation ◽  
Good Agreement

Abstract. In the present study, the WRF-CHEM model is used to evaluate the contributions of trans-boundary transport to the air quality in Beijing during a persistent air pollution episode from 5 to 14 July 2015 in Beijing-Tianjin-Hebei (BTH), China. Generally, the predicted temporal variations and spatial distributions of PM2.5 (fine particulate matter), O3 (ozone), and NO2 are in good agreement with observations in BTH. The WRF-CHEM model also reproduces reasonably well the temporal variations of aerosol species compared to measurements in Beijing. The factor separation approach is employed to evaluate the contributions of trans-boundary transport of emissions outside of Beijing to the PM2.5 and O3 levels in Beijing. On average, in the afternoon during the simulation episode, the pure local emissions contribute 22.4 % to the O3 level in Beijing, less than 36.6 % from pure emissions outside of Beijing. The O3 concentrations in Beijing are decreased by 5.1 % in the afternoon due to interactions of local emissions with those outside of Beijing. The pure emissions outside of Beijing play a dominant role in the PM2.5 level in Beijing, with a contribution of 61.5 %, much more than 13.7 % from pure Beijing local emissions. The emissions interactions enhance the PM2.5 concentrations in Beijing, with a contribution of 5.9 %. Therefore, the air quality in Beijing is primarily determined by the trans-boundary transport of emissions outside of Beijing during summertime, showing that the cooperation with neighboring provinces to mitigate pollutant emissions is a key for Beijing to improve air quality. Considering the uncertainties in the emission inventory and the meteorological field simulations, further studies need to be performed to improve the WRF-CHEM model simulations to reasonably evaluate trans-boundary transport contributions to the air quality in Beijing for supporting the design and implementation of emission control strategies.

Designing of Solar Water Bath Heater for Gas Pressure Reducing Station in of 150,000 Nm3/h Capacity in Assaluyeh Region in Iran

2010 ◽  
Author(s):  
Fatemeh Dalir ◽  
Morteza Khalaji Assadi
Keyword(s):  
Loss Factor ◽  
Open Circuit ◽  
Water Bath ◽  
Inlet Temperature ◽  
Tube Heat Exchanger ◽  
Solar Water ◽  
Solar Intensity ◽  
Collector Temperature ◽  
Shell And Tube ◽  
Good Agreement

This paper proposes the design of a solar water bath heater for Central Power Plant in Assaluyeh region in south of Iran with the latitude of 27 °N. This heater uses flat plate solar collectors in an open circuit system. Solar intensity, absorbed radiation and ambient temperature are the regional parameters which are known to the designer. The temperature of the bath of water which is the outlet collector temperature (70 °C) belongs to the known parameters in the mentioned station. Flow rate, heat loss factor, the inlet temperature of the collector and the area which is the most important factor to evaluate the economical issues of the system are calculated with modeling the water bath with a shell and tube heat exchanger. The solar water bath heater is then simulated with TRNSYS software. The obtained results are in good agreement with analytical solution based on Duffie and Beckman method.

A Note on the Estimation of Nonlinear System Damping

2003 ◽  
Vol 70 (3) ◽  
pp. 449-450 ◽  
Author(s):  
P. J. Torvik
Keyword(s):  
Nonlinear System ◽  
Frequency Response ◽  
Response Function ◽  
Loss Factor ◽  
Frequency Response Function ◽  
Maximum Amplitude ◽  
Single Mode ◽  
Half Power

System damping for a single mode in resonance is often estimated from a measurement of the bandwidth of the frequency response function. While the bandwidth is customarily measured between the half-power frequencies, it is also possible to choose any other fraction of the maximum amplitude. If the damping is linear, i.e., if the loss factor is independent of amplitude, the same damping will be found with any such choice. While intuition might suggest that the damping of a nonlinear system would be better estimated from a bandwidth taken closer to the maximum amplitude, this is shown to be false.

Fault Tolerant Control of Magnetic Bearings

2001 ◽  
Author(s):  
Uhn Joo Na ◽  
Andrew Provenza ◽  
Alan B. Palazzolo ◽  
Benjamin Choi ◽  
Gerald Montague ◽  
...  
Keyword(s):  
Fault Tolerant ◽  
System Simulation ◽  
Magnetic Bearing ◽  
Rotating Machinery ◽  
Test Results ◽  
Magnetic Forces ◽  
Failure State ◽  
Simulation Results ◽  
Test Verification ◽  
Good Agreement

Abstract This paper provides a new algorithm and test verification for implementing fault-tolerant operation of magnetically suspended, flexible shaft, rotating machinery. The currents to the magnetic bearing are redistributed in a manner so that the bearing actuator preserves the same linearized magnetic forces after some of its coils experience failure. The algorithm that searches a database for the appropriate failure compensation matrix utilizes a Boolean description of the failure state to quickly locate and download its target. The test results are shown to have good agreement with the system simulation results presented.

On the Prediction of Damping in Composite and Sandwich Structures

2001 ◽  
Author(s):  
Victor Birman ◽  
Larry W. Byrd
Keyword(s):  
Composite Laminates ◽  
Loss Factor ◽  
Polymer Matrix Composites ◽  
Sandwich Structures ◽  
Free Vibrations ◽  
Matrix Composites ◽  
Analytical Evaluation ◽  
Numerical Examples ◽  
Mechanics Of Materials ◽  
Good Agreement

Abstract The paper outlines two methodologies for the analytical evaluation of the loss factor in composite laminates and in sandwich structures. One of these methods is based on the analysis of free vibrations, while the second approach utilizes mechanics of materials. The loss factor can be predicted both for specially orthotropic as well as for generally orthotropic laminae, subjected to axial stresses and/or transverse shear. The results for the loss factor of the laminae are in good agreement with available experimental data. As follows from numerical examples, the loss factor of polymer-matrix composites increases with the lamination angle and experiences relatively small variations at large values of these angles.

Topology Optimization of Constrained Damping Layer Treatments

2002 ◽  
Author(s):  
Arnold Lumsdaine
Keyword(s):  
Topology Optimization ◽  
Loss Factor ◽  
Elastic Beam ◽  
Forced Response ◽  
Optimization Process ◽  
Programming Algorithm ◽  
Optimal Topology ◽  
Modal Strain Energy ◽  
Constrained Damping ◽  
Half Power

The aim of this research is to determine the optimal shape of a constrained viscoelastic damping layer on an elastic beam by means of topology optimization. The optimization objective is to maximize the system loss factor for the first resonance frequency of the base beam. All previous optimal design studies on viscoelastic lamina have been size or shape optimization studies, assuming a certain topology for the damping treatment. In this study, this assumption is relaxed, allowing an optimal topology to emerge. The loss factor is computed using the Modal Strain Energy method in the optimization process. Loss factor results are validated by using the half-power bandwidth method, which requires obtaining the forced response of the structure. The ABAQUS finite element code is used to model the structure with two-dimensional continuum elements. The optimization code uses a Sequential Quadratic Programming algorithm. Results show that significant improvements in damping performance, on the order of 100% to 300%, are obtained by optimizing the constrained damping layer topology. A novel topology for the constraining layer emerges through the optimization process.

scholarly journals Damping Determination by Half-Power Bandwidth Method for a Slightly Damped Rectangular Steel Plate in the Mid-Frequency Range

2020 ◽  
Vol 13 (3) ◽  
pp. 177-196
Author(s):  
Marcell Ferenc Treszkai ◽  
David Sipos ◽  
Daniel Feszty
Keyword(s):  
Loss Factor ◽  
Steel Plate ◽  
Sampling Frequency ◽  
Test Case ◽  
Response Functions ◽  
Frequency Range ◽  
Damping Loss Factor ◽  
Simulation Results ◽  
Db Difference ◽  
Half Power

This paper presents a novel methodology for measuring the Damping Loss Factor (DLF) of a slightly damped plate in the mid-frequency range (400-1000 Hz) by the Half Power Bandwidth Method (HPBM). A steel flat plate of 650 x 550 x 2 mm was considered as the test case, which was excited by both a shaker and an impact hammer to quantify the effect of the excitation type for slightly damped plate. Since the HPBM is based on extracting the damping data from the modal resonance peaks, working with the correct Frequency Response Functions (FRF) was found to be a crucial factor. Therefore, the effects of coherence and resolution of the sampling frequency were examined in detail in the measurements. The obtained DLF results were statistically analysed and then applied in SEA simulations. Comparison of the simulation and experimental results showed that the method of extracting the DLF data from the measurements can have as much as 10 dB influence on the simulation results. The best results, with only 2 dB difference between measurement and simulation, were obtained when the statistical expected value of the data was used as the input in the SEA simulations.

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