Modelling the nonlinear behaviour of an underplatform damper test rig for turbine applications

An online coupled state/input/parameter estimation approach for structural dynamics

This work is focused on the topology optimization related to harmonic responses for large-scale problems. A comparative study is made among mode displacement method (MDM), mode acceleration method (MAM) and full method (FM) to highlight their effectiveness. It is found that the MDM results in the unsatisfactory convergence due to the low accuracy of harmonic responses, while MAM and FM have a good accuracy and evidently favor the optimization convergence. Especially, the FM is of superiority in both accuracy and efficiency under the excitation at one specific frequency; MAM is preferable due to its balance between the computing efficiency and accuracy when multiple excitation frequencies are taken into account.

A comparative study of dynamic analysis methods for structural topology optimization under harmonic force excitations

Nonlinear modeling of structures with bolted joints: A comparison of two approaches based on a time-domain and frequency-domain solver

https://repository.tudelft.nl/islandora/object/uuid%3Ab0a01fa0-2226-4e91-ab23-3cddc78c2c4b/datastream/OBJ/download

POD-DEIM model order reduction for strain softening viscoplasticity

http://www.dct.tue.nl/New/Wouw/JSV2013_Besselink.pdf

A comparison of model reduction techniques from structural dynamics, numerical mathematics and systems and control

In this paper, popular model reduction techniques from the fields of structural dynamics, numerical mathematics and systems and control are reviewed and compared. The motivation for such a comparison stems from the fact the model reduction techniques in these fields have been developed fairly independently. In addition, the insight obtained by the comparison allows for making a motivated choice for a particular model reduction technique, on the basis of the desired objectives and properties of the model reduction problem. In particular, a detailed review is given on mode displacement techniques, moment matching methods and balanced truncation, whereas important extensions are outlined briefly. In addition, a qualitative comparison of these methods is presented, hereby focussing both on theoretical and computational aspects. Finally, the differences are illustrated on a quantitative level by means of application of the model reduction techniques to a common example.

In automotive industry, design decisions are increasingly based on virtual prototypes, such as numerical Finite Element (FE) models. This reduces the need for expensive physical prototypes, so that design cost and time-to-market can be reduced. These FE models are deterministic, implicitly assuming that all design parameters are precisely known and that the manufacturing process produces identical structures. This is typically not valid. Uncertainty exists in the manufacturing process, in the physical and geometrical properties and in the environmental conditions. A single deterministic analysis is not sufficient to fully understand their effect on the structural and vibro-acoustic performance. Including possibilistic models of design variables into the mechanical simulation process can lead to an improved design process so as to guarantee the robustness of the design with a fuzzy approach. In this paper, the benefits of this approach are demonstrated on an industrial windshield structure. Measurements of the dynamic response of the windshield have been collected in free-free conditions for nominally identical windshields at different temperatures. A validated FE model in the frequency range of interest has been used. Uncertainty in its physical and geometrical parameters has been obtained from test data and has been introduced in the numerical model in order to assess the effects on the dynamic response. The outcome of the analysis consists of a possibilistic model of the frequency response function, given the the uncertainty in the input parameters. This analysis not only provides a better insight into the effects of uncertainty in the dynamic response prediction, but also provides sensitivity measures of the design parameters on the final performance of the structure. In addition, guidelines to further improve structural designs and manufacturing processes are also obtained.

Modelling of a vehicle windshield with realistic uncertainty

vibro-Lanczos, a symmetric Lanczos solver for vibro-acoustic simulations

A new iterative method for the prediction of dynamic characteristics of coupled vibro-acoustic systems is presented in this study. The proposed method extracts the eigenvectors in a specified frequency band and it is similar in concept to the well-known eigenvalue solvers, such as the Lanczos method. At each iteration step a reduction subspace is built and the problem is projected onto this subspace which is built up from a combination of the so-called correction vectors and the uncoupled modes. The correction vectors are used to correct the starting uncoupled modes of the coupled physics. In the iterations, the uncoupled modes, correction vectors and frequencies are updated. Correction vectors are found by the use of an iterative solution method. Namely, the conjugate gradient method is used along with spectral expansion properties of the matrices to end up with an extremely efficient preconditioner. However, to save some computational cost, an iteration limit is used for the iterative solution process. These vectors are shown to enrich the reduction space in an iterative sense. Concerning the developed method, some test applications are provided.

Umut Tabak

Papers

A comparison of model reduction techniques from structural dynamics, numerical mathematics and systems and control

A comparison of model reduction techniques from structural dynamics, numerical mathematics and systems and control

Modelling of a vehicle windshield with realistic uncertainty

vibro-Lanczos, a symmetric Lanczos solver for vibro-acoustic simulations

A Spectrally Preconditioned Iterative Reduced Correction Algorithm for Vibro-acoustic Problems