SmartCAE - Correlazione FEA-Test

Correlazione tra FEA e Test

f.palloni — Mon, 26 Sep 2011 09:46:27 +0000

Questo articolo introduce la motivazione ed i vantaggi attesi dalla correlazione fra FEA e test sperimentale.

Tipiche applicazioni si trovano nell’ambito dell’analisi modale, dove strutture e procedure efficienti sono, al giorno d’oggi, disponibili per la calibrazione dei modelli analitici, al fine di una miglior corrispondenza con i risultati dei modelli sperimentali.

Viene qui offerta una panoramica degli strumenti d’uso, assieme alla prospettiva di dover tenere in considerazione l’incertezza, analogamente ad una visione futura della tecnologia.

A cura di Eddy Dascotte, Dynamic Design Solutions, Leuven, Belgium

Traduzione a cura del dr. Giuseppe Miccoli, IMAMOTER, CNR, Ferrara

Model Updating of the Ironworkers Memorial Second Narrows Bridge, Vancouver, Canada.

f.palloni — Thu, 09 Jun 2011 14:18:08 +0000

The Ironworkers Memorial Second Narrows Crossing is a critical transportation link in the Lower Mainland Region of British Columbia, Canada, which is a zone of high seismic risk. The IMSNC is being instrumented as part of a real time seismic and health monitoring system, which will also include many other bridges around the region. As part of the system, a finite element model has been developed and updated using previously obtained ambient vibration measurements. This paper focuses on updating of one approach truss section of the bridge. The model was updated in several steps using both manual and automated techniques. Updating included stiffness of a set of seismic isolators that were added to the bridge in a retrofit in the mid 1990’s. The complete updated set of models will be used in fatigue and damage studies as a part of the monitoring system.

M. Turek, C.E. Ventura, E. Dascotte

Presented at the 28th International Modal Analysis Conference (IMAC), February 2010, Jacksonville, Florida, USA.

Model Updating using Operational Data

f.palloni — Thu, 09 Jun 2011 14:11:53 +0000

Finite element model updating is a well established method for validating and improving simulation models in structural dynamics. The traditional approach consists of correlating simulation data with the results of an experimental modal analysis (EMA). Usually, EMA data, i.e. resonance frequencies and mode shapes extracted from frequency response functions, is used as reference since it is independent of the applied loads.
However, the operational loads or boundary conditions can change the dynamic behavior of a structure, or make it impossible to perform an experimental modal analysis. In such cases, only operational data can be used as reference data for model updating. Additionally, updating a model using operational data automatically guaranties the validity of the model under the considered operational conditions.
This paper introduces a new updating approach based on Operational Deflection Shapes (ODS) that is able to update the mass, stiffness and damping properties of a structure simultaneously. The proposed method is evaluated by means of a simulated experiment.

T. Lauwagie, J. Guggenberger, J. Strobbe, E. Dascotte.

Presented at the International Seminar on Modal Analysis 2010 (ISMA), September 20-22, 2010, Leuven, Belgium.

The Impact of High-Fidelity Model Geometry on Test-Analysis Correlation and FE Model Updating Results

f.palloni — Thu, 09 Jun 2011 13:59:59 +0000

Structural responses obtained with finite element simulations normally differ from those measured on physical prototypes. In the case of monolithic structures, the differences between the simulated and measured responses are mainly caused by inaccuracies in the geometry and material behavior. The present work focuses on evaluating the impact of using a high-fidelity representation of the actual geometry on the differences between measured and computed resonant frequencies and mode shapes.
This paper presents a study that was performed on a cast-iron lantern housing of a gear box. In a first step, the resonant frequencies and modes shapes of the test structure were measured using impact testing. Next, optical scanning and photogrammetric techniques were used to obtain a 3D virtual point cloud model which accurately describes the surface of the lantern housing. This point cloud was then used to generate a 3D solid finite element model representing the as-built geometry of the housing.

To evaluate the impact of using the actual geometry on the correlation and model updating results, two FE-models were used: an FE-model derived from the measured geometry and an FE-model derived from the CAD model of the lantern housing. Both models have a similar mesh density and mesh quality. These two models were first correlated with the measured modal data and then updated. The geometry appeared to have a significant impact on both the correlation and updating results.

T. Lauwagie, F. Van Hollebeke, B. Pluymers, R. Zegels, P. Verschueren, E. Dascotte.

Geometry-based Updating of 3D Solid Finite Element Models

f.palloni — Thu, 09 Jun 2011 13:52:30 +0000

Structural responses obtained with finite element (FE) simulations normally differ from those measured on physical prototypes. In the case of monolithic structures, the differences between the simulated and measured responses are mainly caused by inaccuracies in the geometry and material modeling. Such inaccuracies may result from the manufacturing process. The presented work illustrates how the geometry of CAD-based FE-models can be updated using a high-fidelity representation of the actual manufactured geometry, to improve the correlation between measured and computed resonant frequencies and mode shapes.

The study presented in this paper was performed on a cast iron lantern housing of a gear box. In a first step, the resonant frequencies and modes shapes of the test structure were measured using impact testing. Next, a set of digital pictures were taken from a number of different angles. By means of photogrammetry, these pictures were converted into a surface model that represented the actual geometry of the lantern housing. This surface model was then compared with an FE-model derived from a CAD-model of the lantern housing.

Linking FEA with Test

f.palloni — Tue, 07 Apr 2009 13:35:10 +0000

This article introduces the motivation and expected benefits of linking FEA and testing. Typical applications are found in the field of modal analysis where frameworks and efficient procedures are now available for calibrating analytical models to better correspond with the results of experimental models. An overview of the tools is provided together with a scenario for including uncertainty management as well as a future outlook of the technology.

Author

Eddy Dascotte - Dynamic Design Solutions, N.V., Leuven, Belgium

Keywords

fe model validation, correlation, dynamics, modal analysis, model updating

Dynamic Properties Assesment and Updating of Large Diesel Ship Engine

f.palloni — Tue, 07 Apr 2009 12:49:37 +0000

Large diesel engines are a challenging product for engineer: they are large, heavy, dangerous. Modelling is lengthy and cumbersome, testing is expensive and specific. In this paper, the authors will highlight some of these problems and their influences in the correlation between test and numerical data set, and at the same time show that a good match between numerical simulations and test can be achieved with the appropriate procedure. The paper reports about the analysis and updating of a "genset", an aggregate formed by tree main parts: the diesel engine, the electric generator and the common base frame. These three elements combined weight roughly 200 tons, occupying a space of about 260 cubic meters.

Authors

Carlo Pestelli, Fabio Castellani - Wärtsila Italia
Francesco Palloni - SmartCAE
Luigi Bregant - Dipartimento di Ingegneria Meccanica, Università di Trieste

Keywords

fe model validation, correlation, modal analysis, diesel engine