Correlation of the SPICE Beam Expander Structural Model With Component and System Level Modal Test Results

1993 ◽  
Author(s):  
Mark E. Mimovich
Keyword(s):  
Structural Model ◽  
Structural Parameters ◽  
System Level ◽  
Mode Shapes ◽  
Test Results ◽  
Modal Assurance Criterion ◽  
Test Analysis ◽  
Measurement Systems ◽  
Modal Test ◽  
Beam Expander

Abstract A full scale experimental beam expander structure is modeled and correlated with modal test results on a component and system level. Correlation of the FE models is completed using the LINK module of the Leuven Measurement Systems (LMS) software which is also used to acquire and reduce the modal test data. The correlation tools used to measure the agreement between test and analytic mode shapes are the Modal Assurance Criterion (MAC), Coordinate Modal Assurance Criterion (CoMAC), and mass cross-orthogonality. In addition to the tools used to measure agreement between test and analysis modal parameters, sensitivity and optimization algorithms are used to identity structural parameters which influence a particular mode and what the minimum change(s) must be in the parameter(s) to bring about the desired agreement. As part of a system level pre-test analysis, the theoretical mode shapes along with a normalized line-of-sight error associated with each mode are used to select the best measurement and excitation locations.

Investigating the vibrational behaviour of a rotating two-blade propeller by using a self-tracking method

2018 ◽  
Vol 233 (3) ◽  
pp. 835-847 ◽  
Author(s):  
Mohammad-Reza Ashory ◽  
Farhad Talebi ◽  
Heydar R Ghadikolaei ◽  
Morad Karimpour
Keyword(s):  
Natural Frequency ◽  
Measurement Errors ◽  
Mode Shapes ◽  
Model Parameters ◽  
Test Results ◽  
Modal Assurance Criterion ◽  
Tracking Method ◽  
Strong Resemblance ◽  
Test Scenarios ◽  
Good Agreement

This study investigated the vibrational behaviour of a rotating two-blade propeller at different rotational speeds by using self-tracking laser Doppler vibrometry. Given that a self-tracking method necessitates the accurate adjustment of test setups to reduce measurement errors, a test table with sufficient rigidity was designed and built to enable the adjustment and repair of test components. The results of the self-tracking test on the rotating propeller indicated an increase in natural frequency and a decrease in the amplitude of normalized mode shapes as rotational speed increases. To assess the test results, a numerical model created in ABAQUS was used. The model parameters were tuned in such a way that the natural frequency and associated mode shapes were in good agreement with those derived using a hammer test on a stationary propeller. The mode shapes obtained from the hammer test and the numerical (ABAQUS) modelling were compared using the modal assurance criterion. The examination indicated a strong resemblance between the hammer test results and the numerical findings. Hence, the model can be employed to determine the other mechanical properties of two-blade propellers in test scenarios.

An effective method for damage assessment based on limited measured locations in skeletal structures

2020 ◽  
Vol 24 (1) ◽  
pp. 183-195 ◽  
Author(s):  
Parsa Ghannadi ◽  
Seyed Sina Kourehli
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Damage Detection ◽  
Degrees Of Freedom ◽  
Truss Structures ◽  
Mode Shapes ◽  
Analysis Model ◽  
Test Analysis ◽  
Modal Test ◽  
Artificial Neural

This article proposes a new damage detection method using Modal Test Analysis Model and artificial neural networks. A challenge in damage detection problems is lack of measured degrees of freedom, as well as limitations of attached sensors. Modal Test Analysis Model has been used in order to estimate unmeasured degrees of freedom. An experimental cantilever beam was used to show Modal Test Analysis Model’s efficiency in estimation of unmeasured mode shapes. To solve the inverse problem of damage detection, mode shapes estimated by Modal Test Analysis Model were used as inputs, and characteristics of the damage served as outputs of the artificial neural network. The sensitivity analysis carried out for each example showing the performance of artificial neural network after mode shape expansion was efficiently improved. Three numerical examples for plane and space truss structures are considered, in order to verify effectiveness of the proposed method. Results demonstrate a high accuracy of Modal Test Analysis Model and artificial neural network for structural damage detection.

scholarly journals Two-stage Bayesian system identification using Gaussian discrepancy model

2020 ◽  
pp. 147592172093352
Author(s):  
Feng-Liang Zhang ◽  
Siu-Kui Au ◽  
Yan-Chun Ni
Keyword(s):  
System Identification ◽  
Structural Model ◽  
Structural Parameters ◽  
Stage Ii ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Model Parameters ◽  
Modeling Error ◽  
Two Stage ◽  
Classical Statistics

System identification aims at updating the model parameters (e.g. mass and stiffness) associated with the mathematical model of a structure based on measured structural response. In this process, a two-stage approach is commonly adopted. In Stage I, modal parameters including natural frequencies and mode shapes are identified. In Stage II, the modal parameters are used to update structural parameters such as those related to stiffness, mass, and boundary conditions. A recent Bayesian formulation allows the identification results in the first stage to be incorporated in the second stage directly via Bayes’ rule without using a heuristic model (often based on classical statistics) that transfers the information from Stages I to II. This opens up opportunities for explicitly accounting for modeling error in the structural model (Stage II) through the conditional distribution of modal parameters given structural model parameters. Following this approach, this article investigates a methodology where the modeling error between the two stages is incorporated with Gaussian distributions whose statistical parameters are also updated with available data. Leveraging on special mathematical structure induced by the model, computational issues are resolved and an analytical investigation is performed that yields insights on the role of modeling error and whether its statistics can be distinguished from those of identification uncertainty (defined for given structural model). The proposed methodology is verified using synthetic data and applied to a laboratory-scale structure.

Mounting Stiffness Effects in “Free-Free” Modal Tests

1997 ◽  
Author(s):  
Joseph A. Wolf
Keyword(s):  
Support System ◽  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
A Priori ◽  
Mode Shapes ◽  
Vibration Test ◽  
Complex Structures ◽  
Fundamental Issue ◽  
Test Results ◽  
Modal Test

Abstract The fundamental issue confronting a vibration test engineer is how to obtain the best representation for the natural frequencies and corresponding mode shapes of a mechanical system. In the case of a structure such as a vehicle that has rigid body degrees of freedom, a vibration test requires some sort of artificial support system. The purpose of this work is to quantify the influence of this support system using two example structures: a one-degree-of-freedom oscillator, and a uniform beam on two types of supports. In all cases, the actual influence of the supports on the modal test results is greater than one would estimate a priori. It is hoped that these results, which have been derived from exact solutions, will provide insight for designing test supports for more complex structures.

Spacecraft structural model improvement by modal test results

1987 ◽  
Vol 24 (1) ◽  
pp. 90-94 ◽  
Author(s):  
J.-C. Chen ◽  
L. F. Peretti ◽  
J. A. Garba
Keyword(s):  
Structural Model ◽  
Test Results ◽  
Modal Test ◽  
Model Improvement

Modal test/analysis correlation for Centaur G Prime launch vehicle

1986 ◽  
Author(s):  
J. CHEN ◽  
T. ROSE ◽  
M. TRUBERT ◽  
B. WADA ◽  
F. SHAKER
Keyword(s):  
Launch Vehicle ◽  
Test Analysis ◽  
Modal Test

Localization of test/analysis structural model errors

1989 ◽  
Author(s):  
CHAUR-MING CHOU ◽  
JOHN O'CALLAHAN ◽  
CHI-HSING WU
Keyword(s):  
Structural Model ◽  
Model Errors ◽  
Test Analysis

Modal test/analysis correlation of Space Station structures using nonlinear sensitivity

1992 ◽  
Author(s):  
VINEY GUPTA ◽  
JAMES NEWELL ◽  
LASZLO BERKE ◽  
SASAN ARMAND
Keyword(s):  
Space Station ◽  
Test Analysis ◽  
Modal Test

Analysis of Modal Parameters of Adhesively Bonded Double-Strap Joints by the Modal Strain Energy Method

1993 ◽  
Author(s):  
Mohan D. Rao ◽  
Krishna M. Gorrepati
Keyword(s):  
Strain Energy ◽  
Natural Frequencies ◽  
Structural Parameters ◽  
Flexural Vibration ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Adhesively Bonded ◽  
Modal Strain Energy ◽  
Joint System ◽  
Damping Material

Abstract This paper presents the analysis of modal parameters (natural frequencies, damping ratios and mode shapes) of a simply supported beam with adhesively bonded double-strap joint by the finite-element based Modal Strain Energy (MSE) method using ANSYS 4.4A software. The results obtained by the MSE method are compared with closed form analytical solutions previously obtained by the first author for flexural vibration of the same system. Good agreement has been obtained between the two methods for both the natural frequencies and system loss factors. The effects of structural parameters and material properties of the adhesive on the modal properties of the joint system are also studied which are useful in the design of the joint system for passive vibration and noise control. In order to evaluate the MSE and analytical results, some experiments were conducted using aluminum double-strap joint with 3M ISD112 damping material. The experimental results agreed well with both analytical and MSE results indicating the validity of both analytical and MSE methods. Finally, a comparative study has been conducted using various commercially available damping materials to evaluate their relative merits for use in the design of these joints.

Similitudes for vibration characteristic of composite laminated plates

2021 ◽  
pp. 107754632110377
Author(s):  
Fengxia He ◽  
Zhong Luo ◽  
Lei Li ◽  
Xiaoxia Zhang
Keyword(s):  
Natural Frequency ◽  
Prediction Accuracy ◽  
Laminated Plates ◽  
Frequency Mode ◽  
Mode Shapes ◽  
Vibration Characteristic ◽  
Modal Assurance Criterion ◽  
Full Size ◽  
Composite Laminated Plates ◽  
Scaled Models

Similitude laws can be used to extrapolate the vibration characteristic of a small, inexpensive, and easily tested model into structural behavior for the full-size prototype. In this article, a systematic similitude approach is proposed to predict the natural frequency, mode shape, and vibration response of composite laminated plates. The emphasis of this article is to predict the vibration characteristic of composite laminated plates in an effective and convenient way. Sensitivity analysis (SA) is introduced to improve the prediction accuracy of natural frequency. For distortion similarity, the prediction accuracy is improved close to 5%. Modal assurance criterion (MAC) measures the consistency of mode shapes of the full-size prototype and scaled models. The influence of stacking sequence on mode consistency is investigated. Similitude based on virtual mode and statistical energy (SVMSE) is proposed to extrapolate the transient response of the prototype to simulate the shock environment, such as satellite–rocket separation, etc. In conclusion, the prediction accuracy of natural frequency, mode consistency, and response coincidence are considered comprehensively to extrapolate the vibration characteristic of the full-size laminated plates.

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