Finite Element Model Identification Using Modal Data

1994 ◽  
Vol 172 (5) ◽  
pp. 657-669 ◽  
Author(s):  
H. Ahmadian ◽  
G.M.L. Gladwell ◽  
F. Ismail
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Model Identification ◽  
Element Model ◽  
Modal Data

Damage Assessment in Structures Using Incomplete Modal Data and Artificial Neural Network

2015 ◽  
Vol 15 (06) ◽  
pp. 1450087 ◽  
Author(s):  
Seyed Sina Kourehli
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Finite Element ◽  
Finite Element Model ◽  
Structural Damage ◽  
Element Model ◽  
Mass System ◽  
Modal Data ◽  
Artificial Neural ◽  
Propagation Network

This paper presents a novel approach for structural damage detection and estimation using incomplete noisy modal data and artificial neural network (ANN). A feed-forward back propagation network is proposed for estimating the structural damage location and severity. Incomplete modal data is used in the dynamic analysis of damaged structures by the condensed finite element model and as input parameters to the neural network for damage identification. In all cases, the first two natural modes were used for the training process. The present method is applied to three examples consisting of a simply supported beam, three-story plane frame, and spring-mass system. Also, the effect of the discrepancy in mass and stiffness between the finite element model and the actual tested dynamic system has been investigated. The results demonstrated the accuracy and efficiency of the proposed method using incomplete modal data, which may be noisy or noise-free.

Identification of Free-Free Modes From Constrained Vibration Data for Flexible Multibody Models

1999 ◽  
Author(s):  
Tong Y. Yi ◽  
Parviz E. Nikravesh
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Finite Element Model ◽  
Degrees Of Freedom ◽  
Multibody System ◽  
Element Model ◽  
Flexible Body ◽  
Fe Model ◽  
Modal Data ◽  
Vibration Data

Abstract This paper presents a method for identifying the free-free modes of a structure by utilizing the vibration data of the same structure with boundary conditions. In modal formulations for flexible body dynamics, modal data are primary known quantities that are obtained either experimentally or analytically. The vibration measurements may be obtained for a flexible body that is constrained differently than its boundary conditions in a multibody system. For a flexible body model in a multibody system, depending upon the formulation used, we may need a set of free-free modal data or a set of constrained modal data. If a finite element model of the flexible body is available, its vibration data can be obtained analytically under any desired boundary conditions. However, if a finite element model is not available, the vibration data may be determined experimentally. Since experimentally measured vibration data are obtained for a flexible body supported by some form of boundary conditions, we may need to determine its free-free vibration data. The aim of this study is to extract, based on experimentally obtained vibration data, the necessary free-free frequencies and the associated modes for flexible bodies to be used in multibody formulations. The available vibration data may be obtained for a structure supported either by springs or by fixed boundary conditions. Furthermore, the available modes may be either a complete set; i.e., as many modes as the number of degrees of freedom of the associated FE model is available, or it can be an incomplete set.

Finite Element Model Updating for Unsymmetrical Damping System with Genetic Algorithm

2012 ◽  
Vol 166-169 ◽  
pp. 2999-3003 ◽  
Author(s):  
Bao Qiang Zhang ◽  
Guo Ping Chen ◽  
Qin Tao Guo
Keyword(s):  
Genetic Algorithm ◽  
Finite Element ◽  
Finite Element Model ◽  
Model Updating ◽  
Element Model ◽  
Maximum Error ◽  
Optimization Method ◽  
Finite Element Model Updating ◽  
Modal Data ◽  
Complex Modal

Finite element model updating using incomplete complex modal data for unsymmetrical damping system with genetic algorithm is presented. The genetic algorithm method and finite element model updating based on optimization method using complex modal eigenvalue are introduced. The updating for simulation example about a flexible rotor system which is a typical unsymmetrical damping system is performed using bearing stiffness, bearing damping and diameter moment of inertia parameters. The results show that the maximum error of updated parameters is 0.15% and the objective function of genetic algorithm is 0.0081. The study demonstrates that the finite element model updating method using incomplete complex modal data with genetic algorithm is feasible and effective for unsymmetrical damping system.

Extraction of Free-Free Modes from Constrained Vibration Data for Flexible Multibody Models

2001 ◽  
Vol 123 (3) ◽  
pp. 383-389 ◽  
Author(s):  
Tong Y. Yi, ◽  
Parviz E. Nikravesh
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Finite Element Model ◽  
Degrees Of Freedom ◽  
Multibody System ◽  
Element Model ◽  
Flexible Body ◽  
Fe Model ◽  
Modal Data ◽  
Vibration Data

This paper presents a method for identifying the free-free modes of a structure by utilizing the vibration data of the same structure with boundary conditions. In modal formulations for flexible body dynamics, modal data are primary known quantities that are obtained either experimentally or analytically. The vibration measurements may be obtained for a flexible body that is constrained differently than its boundary conditions in a multibody system. For a flexible body model in a multibody system, depending upon the formulation used, we may need a set of free-free modal data or a set of constrained modal data. If a finite element model of the flexible body is available, its vibration data can be obtained analytically under any desired boundary conditions. However, if a finite element model is not available, the vibration data may be determined experimentally. Since experimentally measured vibration data are obtained for a flexible body supported by some form of boundary conditions, we may need to determine its free-free vibration data. The aim of this study is to extract, based on experimentally obtained vibration data, the necessary free-free frequencies and the associated modes for flexible bodies to be used in multibody formulations. The available vibration data may be obtained for a structure supported either by springs or by fixed boundary conditions. Furthermore, the available modes may be either a complete set, having as many modes as the number of degrees of freedom of the associated FE model, or an incomplete set.

Prediction of Modal Characteristics due to Design Change

1997 ◽  
Author(s):  
Tong Y. Yi ◽  
Parviz E. Nikravesh
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Stiffness Matrix ◽  
Element Model ◽  
Vibration Characteristics ◽  
Original Structure ◽  
Design Change ◽  
Modal Data ◽  
Modal Characteristics

Abstract This paper presents a method for predicting modal characteristics of a structure that is considered to undergo a design change. It is assumed that for the original structure the modal data is available either as a complete or as an incomplete set. Based on the available modal data and the known data on the design change, this paper discusses methodologies for determining the vibration characteristics of the modified structure. By considering practical situations, the emphasis of this paper is on structures for which a finite element model, and hence a stiffness matrix, is not available.

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