Correlazione FEA-Test

Correlazione tra FEA e Test

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.

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

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.

Model Updating using Operational Data

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.

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

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.

Geometry-based Updating of 3D Solid Finite Element Models

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.

Linking FEA with Test

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.

Dynamic Properties Assesment and Updating of Large Diesel Ship Engine

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.