CSMA 2024 : Hybrid FEM/test twin building, an electric engine case history

SDTools will be present at the CSMA 2024 conference https://csma2024.sciencesconf.org/

The talk [1] to be given will address challenges associated to the generation of a Hybrid FEM/test twin model of an automotive electric car engine in partnership with Stellantis:

  • Describing test outputs
    The electric engine case study being detailed combines strong dominance of harmonic responses and un-measured inputs. The harmonic balance vector signal model chosen gives a space/time/frequency approximation of the response.
  • Choosing model parameters
    Geometry, contacts in bolted joints and laminated stacks, non-linear viscoelastic bushings have here a notable impact.
  • Building a reduced parametric model
    This provides a 2 to 3 orders of magnitude speedup that is necessary for any practical application.
  • Building a Hybrid FEM/test twin model
    Test and FEM are combined using an expansion-based state/parameter estimation process.

[1] https://csma2024.sciencesconf.org/499609/document

Tutorial at SURVISHNO

Error characterization in modal analysis and model updating. An overview of tools and procedures using the Structural Dynamics Toolbox.

will be presented by Etienne Balmès at the SURVISHNO conference in Lyon on July 8, 2019. This tutorial will mix theoretical considerations and applications using SDT (animations https://www.youtube.com/channel/UCy5PHLw70NqfDDvg24tXJWg , presentation www.sdtools.com/pdf/Vishno19_Tutorial.pdf )

Experimental modal analysis seeks to extract shape and resonance properties from test data. While identification algorithms have been well documented for a long time, at least under the assumption linear behavior, significant differences continue to exist in the implementation details. In particular, non-linear optimization of poles and work by sub-bands is an often overlooked necessity to avoid bias. Once modal data available, the next step is to obtain test/analysis correlation. This requires topology correlation which brings its share of errors, which despite being usually small should be addressed. Global correlation criteria, such as the MAC, are introduced next but for efficient use should be complemented by a set of procedures to localize measurement, topology and correlation errors. While the simple evaluation of correlation is often an industrial objective, the best exploitation of test results is achieved using hybrid approaches combining test with a model, which does not need to be exact to usefully complement the measurements. In particular, expansion methods estimating the full Finite Element responses from data measured at sensors are particularly useful. Energy based criteria on the model side (Minimum Dynamic Residual Expansion or the various variants of Error in Constitutive Relation) have been long known to provide excellent solutions but deployment has been scarce due to an important numerical cost. Simple model reduction strategies are shown to give excellent results for industrial models and open the way for model error localization and updating.

The tutorial is illustrated using standard procedures implemented in the Structural Dynamics Toolbox which provides experimental modal analysis, finite element modeling, model reduction and correlation tools in the MATLAB environment. A main brake squeal application serves a red line and is complemented by illustrations from other industries.

Keynote lecture of Etienne Balmès, CEO of SDTools, at the ISMA conference

Etienne Balmès, CEO of SDTools was invited as a keynote speaker at the ISMA (International Symposium on Modal Analysis) conference in Leuven, Belgium on September 17, 2018.

ISMA 2018 is the 28th international conference in a series of annual courses and biennial conferences on structural dynamics, modal testing and noise and vibration engineering, organised by the Department of Mechanical Engineering of the KU Leuven., and is a reference in the field of structural dynamics and vibro-acoustics.

Shapes & DOF: on the use of modal concepts in the context of parametric non-linear studies

copy of the slides (pdf)

Physical responses tend to lie within restricted subspaces even for parametric problems. For a given subspace, the choice of a basis defines Degree Of Freedom (DOF) and this choice may give interesting meaning to the associated amplitudes. Classical modal analysis builds subspaces combining modeshapes and static responses. Parametric loads for non-linear, damped, variable, … structures are discussed to extend the theory and illustrated for test and simulation cases. Challenges in shape extraction and basis generation techniques are then detailed. Introducing the ability to manipulate models with variable junction properties, component material and geometry, load and operating conditions, … opens new questions on the quantification and tracking of changes and objectives throughout design exploration. The definition of a reference linear system and the use of global and/or local modal DOF are shown to provide an interesting perspective.