Joint Parameters Identification of a Structure With Large Number of Discrete Joints

2003 ◽  
Author(s):  
J. H. Wang ◽  
S. C. Chuang
Keyword(s):  
Frequency Response ◽  
Dynamic Behavior ◽  
Error Function ◽  
Parameters Identification ◽  
New Method ◽  
Response Functions ◽  
Traditional Methods ◽  
Measured Frequency Response ◽  
Joint Parameters ◽  
Better Than

The joint parameters of a structure with a large number of discrete joints generally are very difficult to identify accurately. The difficulty is due to the fact that the dynamic behavior of a structure becomes more complex with more number of joints. A new identification method which uses the measured frequency response functions (FRFs) to identify the joint parameters is proposed in this work to overcome this difficulty. The new method uses an error function to select different best data to identify different joints so that the accuracy of the identification can be improved. The accuracy of the new method and other two traditional methods is compared in this work. The results show that the accuracy of the proposed new method is far better than other two previous methods. The proposed new method has special advantage when (1) the number of joints is large, (2) the orders of magnitude of the joint parameters are different significantly.

Calculation of Component Mode Synthesis Matrices From Measured Frequency Response Functions, Part 1: Theory

1998 ◽  
Vol 120 (2) ◽  
pp. 503-508 ◽  
Author(s):  
J. A. Morgan ◽  
C. Pierre ◽  
G. M. Hulbert
Keyword(s):  
Frequency Response ◽  
Component Mode Synthesis ◽  
New Method ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Experimental Implementation ◽  
Measured Frequency Response ◽  
Expansion Coefficients ◽  
Theoretical Developments

This paper presents a new method to calculate the so-called Craig-Bampton component mode synthesis (CMS) matrices from measured frequency response functions. The procedure is based on a modified residual flexibility method, from which the Craig-Bampton CMS matrices are recovered. Experimental implementation of the method requires estimating the modal parameters corresponding to the measured free boundary modes and the Maclaurin series expansion coefficients corresponding to the omitted modes. Theoretical developments are presented in the present paper, Part 1. The performance of the new method is then demonstrated in Part 2 (Morgan et al., 1998) by comparison of experiment and analysis for a simple two-beam system.

scholarly journals A New Method for Analysis of Complex Structures Based on FRF’s of Substructures

2004 ◽  
Vol 11 (1) ◽  
pp. 1-7 ◽  
Author(s):  
C.Q. Liu ◽  
Xiaobo Liu
Keyword(s):  
Frequency Response ◽  
Equations Of Motion ◽  
Complex Structure ◽  
Dynamic Responses ◽  
New Method ◽  
Total System ◽  
Complex Structures ◽  
Response Functions ◽  
Traditional Methods ◽  
Generic Class

A new method is presented for synthesizing the dynamic responses of a complex structure based upon the frequency response functions of the substructures. This method is shown to be superior to traditional methods for several reasons: (i) It can be applied to a generic class of systems. (ii) The analyst is spared the responsibilities of eliminating the coupling forces and rearranging the equations of motion. (iii) The coupling forces and the responses of the total system can be obtained simultaneously and efficiently.

Experimental Identification of Mechanical Joint Parameters

1991 ◽  
Vol 113 (1) ◽  
pp. 28-36 ◽  
Author(s):  
J. H. Wang ◽  
C. M. Liou
Keyword(s):  
Frequency Response ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Theoretical Simulation ◽  
Mechanical Joints ◽  
Experimental Identification ◽  
Mechanical Joint ◽  
Joint Properties ◽  
Measured Frequency Response ◽  
Joint Parameters

The dynamic behavior of a mechanical system generally are strongly affected by the properties of mechanical joints. An identification method which directly used the measured frequency response functions (FRFs) to identify the joint properties was introduced in this work. Because the measurement noise in the frequency response functions is unavoidable in practice and may lead to very faulty results, the proposed method has been developed especially to overcome this problem. The accuracy and feasibility of the proposed method were verified and demonstrated by theoretical simulation and experiments. The results show that the joint properties can be identified accurately from the FRFs even with noise effect.

Calculation of Component Mode Synthesis Matrices From Measured Frequency Response Functions, Part 2: Application

1998 ◽  
Vol 120 (2) ◽  
pp. 509-516 ◽  
Author(s):  
J. A. Morgan ◽  
C. Pierre ◽  
G. M. Hulbert
Keyword(s):  
Frequency Response ◽  
Coupled System ◽  
Companion Paper ◽  
Component Mode Synthesis ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Measured Frequency Response ◽  
Coupled Beams ◽  
The Individual

This paper demonstrates how to calculate Craig-Bampton component mode synthesis matrices from measured frequency response functions. The procedure is based on a modified residual flexibility method, from which the Craig-Bampton CMS matrices are recovered, as presented in the companion paper, Part I (Morgan et al., 1998). A system of two coupled beams is analyzed using the experimentally-based method. The individual beams’ CMS matrices are calculated from measured frequency response functions. Then, the two beams are analytically coupled together using the test-derived matrices. Good agreement is obtained between the coupled system and the measured results.

The Use of Condition Number of a FRF Matrix in Mechanical Parameter Identification

1993 ◽  
Author(s):  
Jhy-Horng Wang ◽  
Chen-Sung Liou
Keyword(s):  
Parameter Identification ◽  
Frequency Response ◽  
Condition Number ◽  
Singular Value ◽  
Measurement Noise ◽  
Mechanical Parameter ◽  
Identification Algorithm ◽  
Response Functions ◽  
Mechanical Joints ◽  
Joint Parameters

Abstract A new identification algorithm is proposed in this work to identify the parameters of mechanical joints. The method considers the whole structure as two substructures which are connected by the joints to be identified. The frequency response functions of the whole structure and substructures are used to extract the joint parameters. In contrast to the traditional methods, only a FRF matrix is needed to inverse in the proposed method. Therefore, it is possible to calculate the condition number of the FRF matrix before the identification. The condition number is defined as the ratio of the maximum singular value divided by the minimum one of a matrix. The condition number of noise contaminated FRF matrix can be used to indicate the sensitivity of the FRF matrix to measurement noise. Therefore, the condition number can be used to avoid the ill-conditioned problem by eliminating the ill-conditioned FRF in some frequency ranges before identification. The simulated results show that the proposed method can significantly improve the accuracy of identification.

Detection of Local Damage of Flexural Member Using Measured Frequency Response Functions

2018 ◽  
Vol 23 (No 3, September 2018) ◽  
pp. 314-320
Author(s):  
Eun-Taik Lee ◽  
Hee-Chang Eun
Keyword(s):  
Damage Detection ◽  
Frequency Response ◽  
Damage Index ◽  
External Noise ◽  
Local Damage ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Measured Frequency Response ◽  
Proper Orthogonal

Measurements by sensors provide inaccurate information, including external noises. This study considers a method to reduce the influence of the external noise, and it presents a method to detect local damage transforming the measured frequency response functions (FRFs) to reduce the influence of the external noise. This study is conducted by collecting the FRFs in the first resonance frequency range from the responses in the frequency domain, taking the mean values at two adjacent nodes, and transforming the results to the proper orthogonal decomposition (POD). A damage detection method is provided. The curvature of the proper orthogonal mode (POM) corresponding to the first proper orthogonal value (POV) is utilized as the damage index to indicate the damage region. A numerical experiment and a floor test of truss bridge illustrate the validity of the proposed method for damage detection.

Modeling the Dynamic Behavior of an Inflatable Rigidized Boom in Exposure to Temperature Changes in Space

2009 ◽  
Author(s):  
Neda Darivandi ◽  
Armaghan Salehian
Keyword(s):  
Frequency Response ◽  
Dynamic Behavior ◽  
Thermal Loading ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Temperature Changes ◽  
The Past ◽  
Space Industry

During the past few years inflatable technology has received much attention by space industry due to its significantly reduced launch volume and mass. While this technology meets the mass goals, because of being ultra-light the structures become very susceptible to disturbances in space. One of the main sources of disturbances is the abrupt temperature changes for a satellite upon passing the Earth’s shadow. While much research has been carried out on the static thermal loading for such structures, very little is known about their dynamic behavior with respect to temperature changes. The presented work is intended to fill this gap. The frequency response functions for a 3 meter inflatable rigidized boom for various temperatures are studied and compared using FEA models in ABAQUS.

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