A New Time Domain Multiple Input Modal Analysis Method

1987 ◽  
Vol 109 (4) ◽  
pp. 377-384 ◽  
Author(s):  
D. W. Cho ◽  
K. F. Eman ◽  
S. M. Wu
Keyword(s):  
Modal Analysis ◽  
Time Domain ◽  
Multivariate Time Series ◽  
Mode Shapes ◽  
Analysis Method ◽  
Parameter System ◽  
Oscillatory Systems ◽  
Structural Test ◽  
Lumped Parameter ◽  
Multiple Input

A time domain approach for multiple input modal analysis of oscillatory systems is proposed. The mathematical foundation for the approach is given along with its applications to a simulated lumped parameter system and the structural dynamics analysis of a milling machine. It has been shown that the proposed multivariate time series models are able to identify the complex mode shapes from multiple input structural test data. The advantages of the proposed method in comparison to existing methods are also highlighted.

The Vibration Analyses of Motorcycle Exhaust System and Suspension-Point Improvement

2011 ◽  
Vol 105-107 ◽  
pp. 200-203
Author(s):  
Guo You Hu ◽  
Pin Qi Xia ◽  
Xing Xing Wang ◽  
Wen Feng Lu
Keyword(s):  
Modal Analysis ◽  
Exhaust System ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Response Analysis ◽  
Finite Model ◽  
Analysis Method ◽  
Element Analysis ◽  
Laboratory Equipment ◽  
Before And After

For the relatively strong vibration caused by a three-wheeled motorcycle exhaust system and raised the level of the noise in the whole motorcycle, this paper combines the experimental modal analysis method and finite element analysis (FEA) method, establishes finite model of the exhaust system, finishes the experimental modal analysis and transient response analysis based on Hyperworks software and laboratory equipment, and obtains six natural frequencies and mode shapes. Comparison has been made between acceleration RMS changes before and after the mounting points changed with the transient excitations. At the end, the document also verifies better results after the improvement and found the basement of reducing noise in the next step.

scholarly journals Forced Vibration of a Timoshenko Beam Subjected to Stationary and Moving Loads Using the Modal Analysis Method

2017 ◽  
Vol 2017 ◽  
pp. 1-26 ◽  
Author(s):  
Taehyun Kim ◽  
Ilwook Park ◽  
Usik Lee
Keyword(s):  
Modal Analysis ◽  
Timoshenko Beam ◽  
Forced Vibration ◽  
Natural Frequencies ◽  
Dynamic Responses ◽  
Mode Shapes ◽  
Timoshenko Beams ◽  
Moving Loads ◽  
Analysis Method ◽  
Simply Supported

The modal analysis method (MAM) is very useful for obtaining the dynamic responses of a structure in analytical closed forms. In order to use the MAM, accurate information is needed on the natural frequencies, mode shapes, and orthogonality of the mode shapes a priori. A thorough literature survey reveals that the necessary information reported in the existing literature is sometimes very limited or incomplete, even for simple beam models such as Timoshenko beams. Thus, we present complete information on the natural frequencies, three types of mode shapes, and the orthogonality of the mode shapes for simply supported Timoshenko beams. Based on this information, we use the MAM to derive the forced vibration responses of a simply supported Timoshenko beam subjected to arbitrary initial conditions and to stationary or moving loads (a point transverse force and a point bending moment) in analytical closed form. We then conduct numerical studies to investigate the effects of each type of mode shape on the long-term dynamic responses (vibrations), the short-term dynamic responses (waves), and the deformed shapes of an example Timoshenko beam subjected to stationary or moving point loads.

scholarly journals Obtaining Dynamic Parameters by Using Ambient Vibration Recordings on Model of The Steel Arch Bridge

2021 ◽  
Author(s):  
Azer A. Kasimzade ◽  
Sertaç Tuhta ◽  
Furkan Günday ◽  
Hakan Aydın
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Modal Analysis ◽  
Dynamic Characteristics ◽  
Operational Modal Analysis ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Dynamic Parameters ◽  
Analysis Method ◽  
Arch Bridge

Operational Modal Analysis (OMA) is a one of the most popular method to extract the dynamic characteristics from ambient vibration response signals. In this study, the dynamic characteristics of a model of steel arch bridge with a bolt connection constructed in a 6.10 m span and 1.88 m height laboratory were determined by finite element method and operational modal analysis methods. Firstly, finite element model was created in SAP2000 software of model steel system and dynamic characteristic were obtained numerically. Then, accelerometers were placed where the displacements are high on points of the system and dynamic characteristics were determined by operational modal analysis method. The aim of this study is to obtain the dynamic parameters (frequency, damping ratio, mode shapes) of the model of the steel arch bridge accurately and reliably by operational modal analysis method by making use of ambient vibrations in the laboratory conditions. For this purpose, analytical analysis of the model of the steel arch bridge with finite element method and the dynamic parameters obtained as a result of the operational modal analysis of the model steel arch bridge were compared. Also, the modal assurance criterion (MAC) was used. Good compatibility was recognized between the results obtained for experimental and numerical procedures in terms of both the natural frequency and the mode of vibration. At the end of this study, reasonable correlation is obtained between mode shapes, frequencies and damping ratios. Analytical and Operational modal frequencies differences between 0.139 %–7.170 %.

Modal Analysis of Aeroengine Turbine Blade-Disc System

2012 ◽  
Vol 487 ◽  
pp. 889-893
Author(s):  
Wei Qiang Zhao ◽  
Yong Xian Liu ◽  
Mo Wu Lu ◽  
Qing Jun Guo
Keyword(s):  
Optimal Design ◽  
Modal Analysis ◽  
Turbine Blade ◽  
Natural Frequencies ◽  
Dynamical Analysis ◽  
Mode Shapes ◽  
Analysis Method ◽  
Safety Verification ◽  
Aero Engine ◽  
Free Status

This paper introduces the FEA method for modal analysis of aero-engine turbine blade-disc system. Natural modal analysis for dynamical analysis and the result can be used as criterion of many dynamics characteristics and further analysis. In this paper, the natural modal of an aero-engine turbine blade-disc system with the turbine joint hole fully constrained and in free status is calculated respectively. And the first ten natural frequencies and mode shapes are obtained. Also, vibration characteristics of each natural modal and the corresponding influence on turbine blade-disc system and other structure are discussed. The analysis method and results in this paper can be used for further study on optimal design and vibration safety verification for the blade-disc system.

Structural Nonlinearity Identification Using Perturbed Eigen Problem and ITD Modal Analysis Method

2012 ◽  
Vol 232 ◽  
pp. 949-954 ◽  
Author(s):  
H. Kashani ◽  
A.S. Nobari
Keyword(s):  
Modal Analysis ◽  
Time Domain ◽  
Nonlinear Dynamic ◽  
Harmonic Balance ◽  
Dynamic Stiffness ◽  
Nonlinear Behavior ◽  
Analysis Method ◽  
Structural Nonlinearity ◽  
Cubic Stiffness ◽  
Good Agreement

Identification of nonlinear behavior in structural dynamics has been considered here, in this paper. Time domain output data of system are directly used to identify system through Ibrahim Time Domain (ITD) modal analysis method and perturbed eigen problem. Cubic stiffness and Jenkins element, as case studies, are employed to qualify the identification method. Results are compared with Harmonic Balance (HB) estimation of nonlinear dynamic stiffness. Results of ITD based identification are in good agreement with the HB estimation, for stiffness parts of nonlinear dynamic stiffness but for damping parts of nonlinear dynamic stiffness, method needs some additional improvements which are under investigation.

Effect of Bass Bar Tension on Modal Parameters of a Violin's Top Plate

2015 ◽  
Vol 39 (1) ◽  
pp. 145-149 ◽  
Author(s):  
Ewa B. Skrodzka ◽  
Bogumił B.J. Linde ◽  
Antoni Krupa
Keyword(s):  
Modal Analysis ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Normal Value ◽  
Modal Damping

Abstract Experimental modal analysis of a violin with three different tensions of a bass bar has been performed. The bass bar tension is the only intentionally introduced modification of the instrument. The aim of the study was to find differences and similarities between top plate modal parameters determined by a bass bar perfectly fitting the shape of the top plate, the bass bar with a tension usually applied by luthiers (normal), and the tension higher than the normal value. In the modal analysis four signature modes are taken into account. Bass bar tension does not change the sequence of mode shapes. Changes in modal damping are insignificant. An increase in bass bar tension causes an increase in modal frequencies A0 and B(1+) and does not change the frequencies of modes CBR and B(1-).

Model Fungsi Transfer Input Ganda untuk Pemodelan Jakarta Islamic Index

2019 ◽  
Vol 7 (3) ◽  
Author(s):  
Nur Laela Fitriani ◽  
Pika Silvianti ◽  
Rahma Anisa
Keyword(s):  
Exchange Rate ◽  
Transfer Function ◽  
Multivariate Time Series ◽  
Model Identification ◽  
Transfer Function Model ◽  
Function Model ◽  
Jones Index ◽  
Multiple Input ◽  
Identification Stage ◽  
Stage Estimation

Transfer function model with multiple input is a multivariate time series forecasting model that combines several characteristics of ARIMA models by utilizing some regression analysis properties. This model is used to determine the effect of output series towards input series so that the model can be used to analyze the factors that affect the Jakarta Islamic Index (JII). The USD exchange rate against rupiah and Dow Jones Index (DJI) were used as input series. The transfer function model was constructed through several stages: model identification stage, estimation of transfer function model, and model diagnostic test. Based on the transfer function model, the JII was influenced by JII at the period of one and two days before. JII was also affected by the USD exchange rate against rupiah at the same period and at one and two days before. In addition, the JII was influenced by DJI at the same period and also at period of one until five days ago. The Mean Absolute Prencentage Error (MAPE) value of forecasting result was 0.70% and the correlation between actual and forecast data was 0.77. This shows that the model was well performed for forecasting JII.

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