scholarly journals Effects of Vibration Modes on the Viscoelastic Loss Factor Measured by the Half-Power Method.

1991 ◽  
Vol 57 (539) ◽  
pp. 2194-2197
Author(s):  
Eiji ADACHI ◽  
junichi SATOH
Keyword(s):  
Loss Factor ◽  
Vibration Modes ◽  
Power Method ◽  
Half Power

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.

Refined Theory of Damped Axisymmetric Vibrations of Double-Layered Cylindrical Shells

1979 ◽  
Vol 21 (1) ◽  
pp. 33-37 ◽  
Author(s):  
Ŝ. Markuŝ
Keyword(s):  
Outer Layer ◽  
Loss Factor ◽  
Longitudinal Vibration ◽  
Cylindrical Shells ◽  
Strong Dependence ◽  
Normal Modes ◽  
Present Theory ◽  
Damping Capacity ◽  
Refined Theory ◽  
Vibration Modes

The governing differential equations of vibrations of double-layered cylindrical shells are derived from classical thinshell theory. The outer layer of the shell is assumed to be viscoelastic, possessing high damping capacity to control vibrations (loss factor, β = 0.3). Decoupled torsional and coupled radial-longitudinal vibration modes are analysed by the method of ‘damped normal modes’. The present theory refines Kagawa and Krokstad's former analysis (1)‡. The results obtained point to a strong dependence of mechanical losses upon the thickness-to-radius ratio, h1/ R, even in the case of axisymmetric modes. This phenomenon was not recognized in Kagawa-Krokstad's approach.

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.

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.

Negative Ten Decibels Method for Damping Identification of Light Damping Structure

2014 ◽  
Vol 577 ◽  
pp. 170-173
Author(s):  
Zhi Wei Guo ◽  
Mei Ping Sheng ◽  
Jian Gang Ma
Keyword(s):  
Accurate Result ◽  
Repeated Measurements ◽  
Power Method ◽  
Structural Damping ◽  
Noise Resistance ◽  
Simulation And Experiment ◽  
Half Power

Half power method is commonly used in structural damping identification because of its simplicity in algorithm. But when the damping is very small, half power method will lead a big error. In order to get more accurate result of small damping structure, this paper suggests using negative ten decibels method (N-10dB) instead of half power method. N-10dB method takes 10-dB bandwidth into consideration, differs from 3-dB of half-power method. The theory of this method is given firstly and proves that it is very simple in algorithm. Subsequent simulation and experiment show that, compared with half power method, N-10dB method have stronger noise resistance, higer precision and is more stable in repeated measurements. Except that, the N-10dB method is also practical in engineering test.

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.

Comparison of damping parameters based on the half-power bandwidth methods of viscous and hysteretic damping models

2021 ◽  
pp. 107754632110546
Author(s):  
Panxu Sun ◽  
Dongwei Wang
Keyword(s):  
Loss Factor ◽  
Damping Ratio ◽  
Relative Difference ◽  
Structural Damping ◽  
Application Condition ◽  
Comparison Results ◽  
First Choice ◽  
Hysteretic Damping ◽  
Approximate Relationship ◽  
Half Power

The half-power bandwidth method is usually used to calculate structural damping parameters by frequency response function (FRF). In this note, the half-power bandwidth methods for the displacement FRF, the velocity FRF, and the acceleration FRF are proposed based on viscous and hysteretic damping models, respectively. Comparison results show that the application conditions of half-power bandwidth methods for the displacement and acceleration FRFs are limited. They can only be used to calculate the small damping ratio/loss factor. The application condition of half-power bandwidth method for the velocity FRF is not limited. It can be used to calculate the large or small damping ratio/loss factor, which should be the first choice for calculating damping parameters. Besides, when the damping ratio is less than 0.2546 or the loss factor is less than 0.5658, the relative difference between the loss factor and twice the damping ratio is less than 10%. With the increase of the damping ratio or loss factor, the relative difference will increase rapidly, and the approximate relationship is no longer applicable.

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