Nonlinear Structural Identification Using a Multi-Harmonic Frequency Response Functions
Licentiatavhandling, 2013

In industrial structural dynamics problems, linear FE-models commonly serve to represent the global structural behavior. However, when test data are available they often show evidence of nonlinear dynamic characteristics. In that case, an initial linear model may be judged insufficient in representing the dynamics of the structure. The causes of the non-linear characteristics may be local in nature whereas the major part of the structure is satisfactorily represented by linear descriptions. Although the initial model can serve as a good foundation, all physical properties required for representing the real structure with high fidelity are most likely not included in the initial model. Therefore, a set of parameterized candidate properties controlling the nonlinear effects have to be added. The selection of the candidates is a delicate task which must be based on insight into the physical processes that control the structure at hand. The focus of this thesis is on the selection of uncertain model parameters together with the forming of the objective function to be used for calibration. To give precise estimation of parameters in the presence of measurement noise, the objective function data have to be informative with respect to the selected parameters. Also, to get useful test data for calibration, the system stimuli need to be properly designed. A multi-harmonic stationary sinusoidal excitation is here considered since the corresponding steady-state responses at the different harmonic orders are shown to contain valuable information for the calibration process.


inverse problem

Nonlinear structure

multi-harmonic frequency response function

finite element model updating

Fisher information matrix

grey box system identification

EE, Hörsalsvägen 11
Opponent: Dr. Martin Magnevall


Vahid Yaghoubi Nasrabadi

Chalmers, Tillämpad mekanik, Dynamik

Automated modal analysis based on frequency response function estimates

Conference Proceedings of the Society for Experimental Mechanics Series. 30th IMAC, A Conference on Structural Dynamics, Jacksonville, 30 January-2 February 2012,; Vol. 5(2012)p. 9-18

Paper i proceeding

Locally Non-linear Model Calibration Using Multi Harmonic Responses: Applied on Ecole de Lyon Non-linear Benchmark Structure

Conference Proceedings of the Society for Experimental Mechanics Series, Topics in Nonlinear Dynamics, Proceedings of the 31st IMAC, A Conference on Structural Dynamics,; Vol. 1(2013)p. 113-123

Paper i proceeding


Teknisk mekanik

Technical report - Department of Applied Mechanics, Chalmers University of Technology, Göteborg, Sweden: 2013:24

EE, Hörsalsvägen 11

Opponent: Dr. Martin Magnevall