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.

A New Methodology for the Accurate and Consistent Identification of Modal Parameters Using Multi-FRF Analysis

1995 ◽  
Author(s):  
R. M. Lin ◽  
S.-F. Ling
Keyword(s):  
Eigenvalue Problem ◽  
Loss Factor ◽  
Frequency Response Function ◽  
Natural Frequencies ◽  
Identification Problem ◽  
Modal Parameters ◽  
Frequency Range ◽  
Case Examples ◽  
Measured Frequency Response ◽  
Damping Loss Factor

Abstract A new method for the estimation of modal parameters is presented in this paper. Unlike the majority of the existing methods which involve complicated curve fitting and interpolative procedures, the proposed method calculates the modal parameters by solving eigenvalue problem of an equivalent eigensystem derived from measured frequency response function (FRF) data. It is developed based on the practical assumption that only one incomplete column of the FRF matrix of the test structure has been measured in a frequency range of interest. All the measured FRFs are used simultaneously to construct the equivalent eigensystem matrices from which natural frequencies, damping loss factor and modeshape vectors of interest can be directly solved. Since the identification problem is reduced to an eigenvalue problem of an equivalent system, natural frequencies and damping loss factors identified are consistent. Further procedures for normalizing the identified eigenvectors so that they become mass-normalized are developed. Numerical case examples are given to demonstrate the practicality of the proposed method and results obtained are indeed very promising. It is believed that with the availability of such identification method, modal analysts’ dream of intelligent and full automatic modal analysis will become a reality.

Damping Loss Factor Estimation for Test-Based Vehicle SEA Modeling

2001 ◽  
Author(s):  
Jae-Hak Woo ◽  
Xiandi Zeng
Keyword(s):  
Loss Factor ◽  
Bias Error ◽  
Reverberation Time ◽  
Frequency Range ◽  
Air Cavity ◽  
Damping Loss Factor ◽  
Factor Estimation

Abstract In the test-based SEA models, the major parameters are measured or estimated from measured quantities. One of the parameters is Damping Loss Factor (DLF) of the air (passenger) cavity of a vehicle. In the SEA model, the air cavity is divided into several sub-cavities. The required DLF for each sub-cavity can be calculated from the reverberation time (T60) measured in that sub-cavity in the vehicle. However, if nothing is done to separate one sub-cavity from other sub-cavities in the T60 measurement in the vehicle, the measured T60 for that sub-cavity is the T60 of the whole air cavity. When the resulted DLF is used in SEA model of that sub-cavity, it is the DLF of the whole air cavity that is used for a sub-cavity, which will result in an over/under-damped. Thus, the prediction from such a SEA model will have bias error especially in the higher frequency range. This has been seen in the results of a vehicle SEA model. In this paper, a method is proposed to estimate the DLF of each sub-cavity based on the T60 of the whole air cavity. When these estimated DLF’s are used in the SEA model for each sub-cavity, the correlation in SEA model was improved by 2.5∼3 dB above 1kHz.

Bond Thickness Effects upon Dynamic Behaviour in Adhesive Joints

2010 ◽  
Vol 97-101 ◽  
pp. 3920-3923 ◽  
Author(s):  
Xiao Cong He
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Dynamic Behaviour ◽  
Adhesive Layer ◽  
Adhesive Joints ◽  
Response Functions ◽  
Frequency Range ◽  
Element Analysis ◽  
Cantilevered Beam ◽  
Different Thickness

The influence of adhesive layer thickness on the dynamic behaviour of the single-lap adhesive joints is investigated in this paper. The ABAQUS finite element analysis (FEA) software was used to predict the frequency response functions (FRFs) of the single-lap adhesive joints of different thickness of the adhesive layer. As a reference, the FRFs of a cantilevered beam without joint were investigated as well. It is clear that the FRFs of the four beams are close to each other within the frequency range 0~1000 Hz. It is also found that the composite damping of the single-lap adhesive joint increases as the thickness of the adhesive layer increases.

A Modified IEEE 118-Bus Test Case for Geomagnetic Disturbance Studies—Part II: Simulation Results

2020 ◽  
Author(s):  
Aboutaleb Haddadi ◽  
Luc Gerin-Lajoie ◽  
Afshin Rezaei-Zare ◽  
Reza Hassani ◽  
Jean Mahseredjian
Keyword(s):  
Geomagnetic Disturbance ◽  
Test Case ◽  
Simulation Results

scholarly journals EXTENSION OF THE FREQUENCY-RANGE OF INTERFEROMETERS FOR THE "MAGNETIC" COMPONENTS OF GRAVITATIONAL WAVES?

2007 ◽  
Vol 22 (13) ◽  
pp. 2361-2381 ◽  
Author(s):  
CHRISTIAN CORDA
Keyword(s):  
Data Analysis ◽  
Frequency Dependence ◽  
Gravitational Waves ◽  
Response Functions ◽  
Frequency Range ◽  
Total Response ◽  
High Frequencies ◽  
Magnetic Components ◽  
Linear Dimensions ◽  
Dominant Part

Recently, with an enlightening treatment, Baskaran and Grishchuk have shown the presence and importance of the so-called "magnetic" components of gravitational waves (GW's), which have to be taken into account in the context of the total response functions of interferometers for GW's propagating from arbitrary directions. In this paper the analysis of the response functions for the magnetic components is generalized in its full frequency dependence, while in the work of Baskaran and Grishchuk the response functions were computed only in the approximation of wavelength much larger than the linear dimensions of the interferometer. It is also shown that the response functions to the magnetic components grow at high frequencies, differently from the values of the response functions to the well-known ordinary components that decrease at high frequencies. Thus the magnetic components could in principle become the dominant part of the signal at high frequencies. This is important for a potential detection of the signal at high frequencies and confirms that the magnetic contributions must be taken into account in the data analysis. More, the fact that the response functions of the magnetic components grow at high frequencies shows that, in principle, the frequency-range of Earth-based interferometers could extend to frequencies over 10000 Hz.

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 Are Single Polymer Network Hydrogels with Chemical and Physical Cross-Links a Promising Dynamic Vibration Absorber Material? A Simulation Model Inquiry

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5127
Author(s):  
Leif Kari
Keyword(s):  
Simulation Model ◽  
Loss Factor ◽  
Polymer Network ◽  
Vibration Absorber ◽  
Vibration System ◽  
Frequency Range ◽  
Dynamic Vibration Absorber ◽  
High Loss ◽  
Dynamic Vibration ◽  
Cross Links

Tough, doubly cross-linked, single polymer network hydrogels with both chemical and physical cross-links display a high loss factor of the shear modulus over a broad frequency range. Physically, the high loss factor is resulting from the intensive adhesion–deadhesion activities of the physical cross-links. A high loss factor is frequently required by the optimization processes for optimal performance of a primary vibration system while adopting a dynamic vibration absorber, in particular while selecting a larger dynamic vibration absorber mass in order to avoid an excess displacement amplitude of the dynamic vibration absorber springs. The novel idea in this paper is to apply this tough polymer hydrogel as a dynamic vibration absorber spring material. To this end, a simulation model is developed while including a suitable constitutive viscoelastic material model for doubly cross-linked, single polymer network polyvinyl alcohol hydrogels with both chemical and physical cross-links. It is shown that the studied dynamic vibration absorber significantly reduces the vibrations of the primary vibration system while displaying a smooth frequency dependence over a broad frequency range, thus showing a distinguished potential for the tough hydrogels to serve as a trial material in the dynamic vibration absorbers in addition to their normal usage in tissue engineering.

scholarly journals Electrocardiogram Sampling Frequency Range Acceptable for Heart Rate Variability Analysis

2018 ◽  
Vol 24 (3) ◽  
pp. 198 ◽  
Author(s):  
Ohhwan Kwon ◽  
Jinwoo Jeong ◽  
Hyung Bin Kim ◽  
In Ho Kwon ◽  
Song Yi Park ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Sampling Frequency ◽  
Heart Rate Variability Analysis ◽  
Frequency Range ◽  
Variability Analysis

scholarly journals Impacts of spatial resolution and representation of flow connectivity on large-scale simulation of floods

2017 ◽  
Author(s):  
Cherry May R. Mateo ◽  
Dai Yamazaki ◽  
Hyungjun Kim ◽  
Adisorn Champathong ◽  
Jai Vaze ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Large Scale ◽  
Flood Hazard ◽  
Regional Scale ◽  
Global Scale ◽  
Test Case ◽  
Efficiency Coefficient ◽  
Computational Power ◽  
Extreme Flood ◽  
Simulation Results

Abstract. Global-scale River Models (GRMs) are core tools for providing consistent estimates of global flood hazard, especially in data-scarce regions. Due to former limitations in computational power and input datasets, most GRMs have been developed to use simplified representation of flow physics and run at coarse spatial resolutions. With increasing computational power and improved datasets, the application of GRMs to finer resolutions is becoming a reality. To support development in this direction, the suitability of GRMs for application to finer resolutions needs to be assessed. This study investigates the impacts of spatial resolution and flow connectivity representation on the predictive capability of a GRM, CaMa-Flood, in simulating the 2011 extreme flood in Thailand. Analyses show that when single downstream connectivity (SDC) is assumed, simulation results deteriorate with finer spatial resolution; Nash–Sutcliffe Efficiency coefficient decreased by more than 35 % between simulation results at 10 km resolution and 1 km resolution. When multiple downstream connectivity (MDC) is represented, simulation results slightly improve with finer spatial resolution. The SDC simulations result in excessive backflows on very flat floodplains due to the restrictive flow directions in finer resolutions. MDC channels attenuated these effects by maintaining flow connectivity and flow capacity between floodplains in varying spatial resolutions. While a regional-scale flood was chosen as a test case, these findings are universal and can be extended to global-scale simulations. These results demonstrate that a GRM can be used for higher resolution simulations of large-scale floods, provided that MDC in rivers and floodplains is adequately represented in the model structure.

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