Modal Data Are Insufficient for Identification of Both Mass and Stiffness Matrices

AIAA Journal ◽  
10.2514/2.36 ◽  
1997 ◽  
Vol 35 (11) ◽  
pp. 1797-1798 ◽  
Author(s):  
Menahem Baruch
Keyword(s):  
Modal Data ◽  
Stiffness Matrices

Symmetric Model Correction of Mechanical Systems

1993 ◽  
Author(s):  
Marca Lam ◽  
Daniel J. Inman ◽  
Andreas Kress
Keyword(s):  
Analytical Model ◽  
Model Updating ◽  
Symmetric Model ◽  
Simple Method ◽  
Modal Data ◽  
Model Correction ◽  
Systems Model ◽  
Modal Damping ◽  
Stiffness Matrices ◽  
Damped Systems

Abstract This work examines the model updating problem for simple nonconservative proportionally damped systems. Model correction, also called model updating, refers to the practice of adjusting an analytical model until the model agrees with measured modal data. The specific case examined here assumes that natural frequencies and modal damping ratios are available from vibration tests and that the measured data disagrees in part with the modal data predicted by an analytical model. Most model correction schemes tend to produce updated damping and stiffness matrices which are asymmetric. The simple method presented here focuses on retaining the desired symmetry in the updated model.

Damage Identification in Continuum Structures From Vibration Modal Data

1997 ◽  
Vol 503 ◽  
Author(s):  
H. P. Chen ◽  
N. Bicanic
Keyword(s):  
Structural Damage ◽  
Damage Identification ◽  
Structural Parameters ◽  
Computational Technique ◽  
Gauss Point ◽  
Continuum Structures ◽  
Modal Data ◽  
Stiffness Matrices ◽  
Direct Iteration ◽  
Vibration Modal

ABSTRACTA novel procedure for damage identification of continuum structures is proposed, where both the location and the extent of structural damage in continuum structures can be correctly determined using only a limited amount of measurements of incomplete modal data. On the basis of the exact relationship between the changes of structural parameters and modal parameters, a computational technique based on direct iteration and directly using incomplete modal data is developed to determine damage in structure. Structural damage is assumed to be associated ith a proportional (scalar) reduction of the original element stiffness matrices, equivalent to a scalar reduction of the material modulus, which characterises at Gauss point level. Finally, numerical examples for plane stress problem and plate bending problem are utilised to demonstrate the effectiveness of the proposed approach.

LS-SVM Regression for Structural Damage Diagnosis Using the Iterated Improved Reduction System

2016 ◽  
Vol 16 (06) ◽  
pp. 1550018 ◽  
Author(s):  
S. S. Kourehli
Keyword(s):  
Structural Damage ◽  
Estimation Method ◽  
Mode Shapes ◽  
Support Vector ◽  
Tuning Parameters ◽  
Modal Data ◽  
Reduction System ◽  
Stiffness Matrices ◽  
Svm Model ◽  
Coupled Simulated Annealing

A damage detection and estimation method is proposed for structural health monitoring using incomplete modal data and least squares support vector machine (LS-SVM). To accommodate the use of incomplete modal data, the iterated improved reduction system (IIRS) method has been used to condense the mass and stiffness matrices of the structure. The first two incomplete mode shapes and natural frequencies of a damaged structure are used as input data to the LS-SVM. The coupled simulated annealing (CSA) and standard simplex method using 10-fold cross-validation techniques are adopted to determine the optimal tuning parameters in the LS-SVM model. Three illustrative examples with and without noise in modal data are prepared to evaluate the performance of the proposed method. The results indicated that this method can be reliably used to identify the damages of structures with good accuracy.

An Optimal Hybrid Expansion—Reduction Damage Detection Method

2003 ◽  
Vol 9 (8) ◽  
pp. 983-995 ◽  
Author(s):  
M. Abdalla ◽  
K. Grigoriadis ◽  
D. Zimmerman
Keyword(s):  
Damage Detection ◽  
Structural Damage ◽  
Hybrid Approach ◽  
Optimization Methods ◽  
Linear Matrix ◽  
Test Bed ◽  
Detection Problem ◽  
Lmi Optimization ◽  
Modal Data ◽  
Stiffness Matrices

In this paper, we examine the structural damage detection problem with an incomplete set of measurements. Linear matrix inequality (LMI) optimization methods are proposed to solve this hybrid damage detection problem that integrates modal data expansion and model reduction with an LMI based damage detection procedure. In the proposed hybrid approach, the transformation matrix is based on the measured data avoiding the use of the healthy mass and stiffness matrices. The method is demonstrated using experimental modal data obtained from the NASA eight-bay cantilevered truss test bed. The experimental results of this hybrid approach are shown to provide a clearer indication of damage than using stand-alone expansion or reduction techniques.

Substructure-Joint Based Approach to Damped FE Model Updating of Complex Assembly Structure

2012 ◽  
Vol 463-464 ◽  
pp. 1169-1174
Author(s):  
Parivash Soleimanian ◽  
Morteza H.Sadeghi ◽  
Akbar Tizfahm
Keyword(s):  
Finite Element ◽  
Model Updating ◽  
Element Model ◽  
Modal Testing ◽  
Fe Model ◽  
Complex Assembly ◽  
Modal Data ◽  
Damping Matrix ◽  
Stiffness Matrices ◽  
Assembly Structure

Model updating techniques are used to update the finite element model of a structure, so that updated model can be predicted the dynamic behavior of an actual assembly structure more accurately. Most of the model updating techniques neglects damping and so amplitudes of vibration at resonance and antiresonance frequencies cannot be predicted by using of these updated models. In dynamic design of structures predicting of these properties is necessary. This paper presents a new technique to create an accurate finite element (FE) updated model of complex assembly structures consisting of substructures and real joint by considering damping of them. Given the fact that modal testing of real joints (such as bolt with some washers) are almost impossible. The updated model of assembly structure is obtained in four steps. In the first step, mass and stiffness matrix of substructures, joint and assembly structure are updated using modal data and Eigen-sensitivity approach. In the second step, damping of assembly structure is identified using complex modal data and updated mass and stiffness matrices which are obtained in first step. In the third step, the effect of damping of joint on frequency response functions (FRFs) extracted from updated model was shown. In the forth step, damping matrix of joint is updated by using FRF-based model updating method and finally damped updated model of assembly structure compared with measured data.

Mass and Stiffness Matrices Updating Using the First Modal Data

2016 ◽  
Vol 851 ◽  
pp. 834-839
Author(s):  
Shi Qi Li ◽  
Zhe Zhang ◽  
Shi Ping Liu ◽  
Heng Zhang
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Modal Data ◽  
First Order ◽  
Stiffness Matrices ◽  
Real Model ◽  
Engineering Computation ◽  
Practical Engineering ◽  
The Difference ◽  
The Finite Element Model

This paper presents a new direct approach to simultaneously update the analytical mass and stiffness matrices in an undamped model .First, we assume that the difference between the finite element model and the real model is little. Second, only by utilizing the first order modal data orthogonal normalization conditions and eigen equations , we derive the updated matrices. Third, the method can maintain matrices symmetry and sparsity and preserve system connectivity. The merit of the proposed method is simple and accurate in a practical engineering computation. Finally,a numerical example is given to demonstrate the accuracy and effectiveness of the presented updating method.

Structural Health Monitoring Using Vibration Measurements and Engineering Insight

1995 ◽  
Vol 117 (B) ◽  
pp. 214-221 ◽  
Author(s):  
D. C. Zimmerman ◽  
M. Kaouk ◽  
T. Simmermacher
Keyword(s):  
Perturbation Theory ◽  
System Identification ◽  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Real World ◽  
Structural Damage ◽  
Practical Experience ◽  
Analytical Models ◽  
Modal Data ◽  
Stiffness Matrices

Several system identification algorithms have been proposed that make use of analytical models and measured modal data to determine the location and/or extent of structural damage. In particular, the authors have proposed a computationally attractive Minimum Rank Perturbation Theory (MRPT) which determines perturbation matrices to the mass, damping, and/or stiffness matrices. Inspection of these perturbation matrices provides insight to both the location and extent of structural damage. This paper documents our practical experience in applying MRPT theory to a variety of structures. The ability to incorporate engineering insight and judgment into the algorithm is shown to enhance the performance of the MRPT technique when faced with real-world issues.

Structural Health Monitoring Using Vibration Measurements and Engineering Insight

1995 ◽  
Vol 117 (B) ◽  
pp. 214-221 ◽  
Author(s):  
D. C. Zimmerman ◽  
M. Kaouk ◽  
T. Simmermacher
Keyword(s):  
Perturbation Theory ◽  
System Identification ◽  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Real World ◽  
Structural Damage ◽  
Practical Experience ◽  
Analytical Models ◽  
Modal Data ◽  
Stiffness Matrices

Several system identification algorithms have been proposed that make use of analytical models and measured modal data to determine the location and/or extent of structural damage. In particular, the authors have proposed a computationally attractive Minimum Rank Perturbation Theory (MRPT) which determines perturbation matrices to the mass, damping, and/or stiffness matrices. Inspection of these perturbation matrices provides insight to both the location and extent of structural damage. This paper documents our practical experience in applying MRPT theory to a variety of structures. The ability to incorporate engineering insight and judgment into the algorithm is shown to enhance the performance of the MRPT technique when faced with real-world issues.

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