Energy Based Comparison of Test and Analysis Response in the Frequency Domain

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Daniel C. Kammer ◽  
Sonny Nimityongskul
Keyword(s):  
Frequency Band ◽  
Stochastic Systems ◽  
Model Updating ◽  
Element Model ◽  
Response Curves ◽  
Test Analysis ◽  
Response Data ◽  
Power Spectral ◽  
Modal Density ◽  
Mean Square Response

Accepted modal based techniques for comparing finite element model and test data for test/analysis correlation and subsequent model updating are impossible to use in the high modal density midfrequency regime. A new approach is presented for comparing test and analysis representations using frequency-based response data instead of modal parameters. The new method uses frequency band averaging of the output power spectral densities with the central frequency of the band running over the complete frequency range of interest. The result of this computation can be interpreted in several different ways but the immediate physical connection is that it produces the mean-square response, or energy, of the system to random input limited to the averaging frequency band. The averaging process is consistent with the averaging done in statistical energy analysis for stochastic systems. The averaged response curves can be compared on a pointwise basis, or they can be compared within a running frequency band.

Frequency Band Averaging of Spectral Densities for Updating Finite Element Models

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Daniel C. Kammer ◽  
Sonny Nimityongskul
Keyword(s):  
Finite Element ◽  
Frequency Band ◽  
Model Updating ◽  
Finite Element Models ◽  
Frequency Range ◽  
Spectral Densities ◽  
Successful Operation ◽  
Test Analysis ◽  
Output Error ◽  
Modal Density

The successful operation of proposed precision spacecraft will require finite element models that are accurate to much higher frequencies than the standard application. The hallmark of this mid-frequency range, between low-frequency modal analysis and high-frequency statistical energy analysis, is high modal density. The modal density is so high, and the sensitivity of the modes with respect to modeling errors and uncertainty is so great that test/analysis correlation and model updating based on traditional modal techniques no longer work. This paper presents an output error approach for finite element model updating that uses a new test/analysis correlation metric that maintains a direct connection to physical response. The optimization is gradient based. The metric is based on frequency band averaging of the output power spectral densities with the central frequency of the band running over the complete frequency range of interest. The results of this computation can be interpreted in several different ways, but the immediate physical connection is that it produces the mean-square response, or energy, of the system to random input limited to the averaging frequency band. The use of spectral densities has several advantages over using frequency response directly, such as the ability to easily include data from all inputs at once, and the fact that the metric is real. It is shown that the averaging process reduces the sensitivity of the optimization due to resonances that plague many output error model updating approaches.

Damage Identification Based on Power Spectral Density Sensitivity Analysis of Structural Responses

2014 ◽  
Vol 919-921 ◽  
pp. 45-50 ◽  
Author(s):  
Wei Huan Chen ◽  
Chang Ying Ding ◽  
Bing Quan He ◽  
Zhong Rong Lv ◽  
Ji Ke Liu
Keyword(s):  
Sensitivity Analysis ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Structural Damage ◽  
Damage Identification ◽  
Model Updating ◽  
Element Model ◽  
Power Spectral ◽  
Structural Responses ◽  
Pseudo Excitation

A new method is proposed to identify structural damages based on the power spectral density sensitivity analysis. The responses of the structure under stationary and random excitations are obtained using pseudo excitation method, and then the sensitivities of power spectral density with respect to the structural damage parameters are obtained similarly. Finite element model updating method is adopted to identify the structural damages. A numerical example of a shearing structure demonstrates the satisfactory results obtained from the present method.

scholarly journals Stiffness Estimation and Equivalence of Boundary Conditions in FEM Models

2021 ◽  
Vol 11 (4) ◽  
pp. 1482
Author(s):  
Róbert Huňady ◽  
Pavol Lengvarský ◽  
Peter Pavelka ◽  
Adam Kaľavský ◽  
Jakub Mlotek
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Boundary Conditions ◽  
Model Updating ◽  
Element Model ◽  
Computational Time ◽  
Stiffness Coefficients ◽  
First Case ◽  
Numerical Approaches

The paper deals with methods of equivalence of boundary conditions in finite element models that are based on finite element model updating technique. The proposed methods are based on the determination of the stiffness parameters in the section plate or region, where the boundary condition or the removed part of the model is replaced by the bushing connector. Two methods for determining its elastic properties are described. In the first case, the stiffness coefficients are determined by a series of static finite element analyses that are used to obtain the response of the removed part to the six basic types of loads. The second method is a combination of experimental and numerical approaches. The natural frequencies obtained by the measurement are used in finite element (FE) optimization, in which the response of the model is tuned by changing the stiffness coefficients of the bushing. Both methods provide a good estimate of the stiffness at the region where the model is replaced by an equivalent boundary condition. This increases the accuracy of the numerical model and also saves computational time and capacity due to element reduction.

A new method for finite element model updating in structural dynamics

2010 ◽  
Vol 24 (7) ◽  
pp. 2137-2159 ◽  
Author(s):  
J.L. Zapico-Valle ◽  
R. Alonso-Camblor ◽  
M.P. González-Martínez ◽  
M. García-Diéguez
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Structural Dynamics ◽  
Model Updating ◽  
Element Model ◽  
New Method ◽  
Finite Element Model Updating
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