| 1. |
- Johansson, Anders, 1982, et al.
(författare)
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An experimental approach to improve controllability in test rigs using passive components
- 2012
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Ingår i: Proceedings, International Conference on Noise and Vibration Engineering, ISMA2012; International Conference on Uncertainty in Structural Dynamics, USD2012. Editors : P. Sas, D. Moens, S. Jonckheere. KU Leuven (Belgium), 17 - 19 September 2012. - 9789073802896 ; , s. 2367-2381
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Konferensbidrag (refereegranskat)abstract
- The first step in successful vibration testing is to calculate input signals such that the test rig accuratelyreplicates the reference signal. The Time Waveform Replication (TWR) method, or augmentations of it, isoften used to this end. TWR and similar methods most often result in a test output which closely replicates,or tracks, the reference signal; however, if there are eigenmodes of the test specimen in the desired frequencyrange of the test which are uncontrollable, it can be shown that the output error cannot be removed beyond theuncontrollable state’s contribution to the reference trajectory. For those specific cases, a method to improvetracking by the use of passive control components designed using a validated finite element (FE) model of thetest specimen has been previously proposed by the authors. In this article we propose instead an experimentalapproach, based on state-space substructure synthesis, to passive control components design for improvedtracking in controllability-lacking test rigs.
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| 2. |
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| 3. |
- Khorsand Vakilzadeh, Majid, 1984, et al.
(författare)
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An improved modal approach for model reduction based on input-output relation
- 2012
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Ingår i: International Conference on Noise and Vibration Engineering (ISMA) / International Conference on Uncertainty in Structural Dynamics (USD). KU Leuven, Dept Mech Engn, Leuven, BELGIUM. SEP 17-19, 2012. - 9789073802896 ; , s. 3451-3459
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Konferensbidrag (refereegranskat)abstract
- An approximated model of a large scale dynamical system captures its main features by a proper selection of its dominant modes. In this paper, a new metric is presented for modal dominancy analysis. This metric is an explicit formulation for evaluating the participation of each mode, independent from the other modes, into the output. Only eigensolutions with a large contribution to this metric, the dominant eigensolutions, will be retained in the approximating lower order model. The modal truncation technique which includes the proposed dominancy analysis not only has a metric for error estimation, but is able to automatically detect and eliminate unobservable and uncontrollable modes. An example from finite element analysis of an aluminum plate illustrates the approach and shows that the proposed method is very efficient in respect to computational time.
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| 4. |
- Krank, Benjamin, et al.
(författare)
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Tuning spot weld models for vehicle body structural dynamics
- 2012
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Ingår i: Proceedings Of International Conference On Noise And Vibration Engineering (ISMA2012) / International Conference On Uncertainty In Structural Dynamics (USD2012). - : Katholieke Universiteit Leuven. - 9789073802896 ; , s. 3915-3926
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Konferensbidrag (refereegranskat)abstract
- Efforts focussing on modelling of spot welds in typical automotive structures have been spent during the last decades resulting in a number of different modelling techniques. One of the crucial aspects common to all these approaches is the difficulties related to the local complexity of the modelling of the actual connections. In order to handle this complexity, spot weld models are often dependent on parameters tuning their characteristics. This paper discusses the tuning of two different spot weld models with respect to certain parameters; the RBE3-Hexa-RBE3 model (also known as the ACM 2) and the Spider2 model available in the pre-processor Ansa. With the current trend towards increasingly refined finite element model meshes, current guide lines need to be updated and elaborated further in order to identify the best performing models. In this paper, model studies are discussed targeting tuning of spot weld parameters together with a new proposal for an exact method for updating the Young's modulus and density of isotropic shell structures analytically using an initial FE calculation.
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| 5. |
- Liu, Hao, et al.
(författare)
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Wave motion and sound transmission loss of double walls filled with porous materials
- 2012
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Ingår i: Proceedings Of International Conference On Noise And Vibration Engineering (ISMA2012) / International Conference On Uncertainty In Structural Dynamics (USD2012). - 9789073802896 ; , s. 1803-1814
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Konferensbidrag (refereegranskat)abstract
- A novel semi-analytical approach is presented and employed to calculate the sound transmission loss (STL) of a double wall lined with porous materials. The approach consists of using the waveguide finite element method (WFEM) together with a Rayleigh-Ritz procedure. The former is a convenient semi-analytical approach useful for structures having constant properties along one direction. The Rayleigh-Ritz procedure assumes that the structure satisfies convenient boundary conditions, so that its response can be described by a trigonometric Fourier series. The advantage of the procedure compared to full FE models, and spectral element models, is that it evaluates several orders of magnitude quicker and can describe frequency dependent materials at virtually no cost. In addition, the WFEM readily provides the dispersion curves of the structure, which reveal its physics. Calculations of the STL are favourably compared to measurements.
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| 6. |
- Struggl, Stephan, 1980, et al.
(författare)
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Wind turbine drive train vibration with focus on gear dynamics under nondeterministic loads
- 2012
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Ingår i: Proceedings, International Conference on Noise and Vibration Engineering, ISMA2012; International Conference on Uncertainty in Structural Dynamics, USD2012. Editors : P. Sas, D. Moens, S. Jonckheere. KU Leuven (Belgium), 17 - 19 September 2012. - 9789073802896 ; , s. 4421-4434
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Konferensbidrag (refereegranskat)abstract
- In present-day, the engineering challenge around a drive train design for a wind turbine is not only to enhancesystem reliability but also to reduce the turbine top mass. These requirements together with the trend of upscaling affect many system characteristics and parameters. The proposed contribution presents a model tostudy torsional drive train vibration dynamics of a generic indirect drive multi-MW wind turbine. The mainfocus lies on developing a fully parameterized computational model of a multi-stage gearbox which fulfillsthe requirement of a proper gear dynamic representation appropriate for multibody formalism as well asthe requirement to be computationally efficient. Two different strategies for modeling the gear contact arestudied and compared in time domain. An analysis of a multi-stage gearbox together with a generator load and a turbine specific nondeterministic excitation was carried out. It is believed that the obtained results will help designer to improve drive train components and to enhance wind turbine reliability and cost efficiency.
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| 7. |
- Van der Kelen, Christophe, 1986-, et al.
(författare)
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Validation of a dedicated test set-up for boundary excitation of trim assemblies
- 2012
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Ingår i: PROCEEDINGS OF INTERNATIONAL CONFERENCE ON NOISE AND VIBRATION ENGINEERING (ISMA2012). - 9789073802896 ; , s. 4051-4060
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Konferensbidrag (refereegranskat)abstract
- A set-up is developed for panel-trim measurements with panel boundary excitation, in order to get a physicalunderstanding of the coupling behaviour between vehicle body and trim layer. Structural excitation in themid-frequency range (150-1000 Hz) is investigated. The construction of the set-up and its global featuresare discussed. Furthermore, a Finite Element model is described, and validated against experimental results.There is good agreement, both quantitatively and qualitatively, between measurements and predictions up to1kHz.
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| 8. |
- Yaghoubi Nasrabadi, Vahid, 1985, et al.
(författare)
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Application of an automated modal analysis based on frequency response function estimates
- 2012
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Ingår i: 25th International Conference on Noise and Vibration engineering, ISMA2012 in conjunction with the 4th International Conference on Uncertainty in Structural Dynamics, USD 2012; Leuven; Belgium; 17 September 2012 through 19 September 2012. - 9789073802896 ; , s. 2145-2155
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Konferensbidrag (refereegranskat)abstract
- Given measured data as estimated frequency responses of a quasi-linear system, there is a variety of system identification methods that identify a state-space model that gives good correlation to the data. Such methods are the N4SID and the PolyMAX methods. Using these methods, a key problem is to select the proper model order. An Automated Modal Analysis was developed in our group to find the proper model order. This method is based on the statistical evaluation of an ensemble of state-space models all identified from the same basic set of frequency response functions, but with different realizations based on a bootstrapping scheme. In this work, we made that method more robust and applied it to two real test data sets.
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| 9. |
- Östberg, Martin
(författare)
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Waves in elastic and poro-elastic cylinders with spatially varying anisotropy
- 2012
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Ingår i: Proceedings Of International Conference On Noise And Vibration Engineering (ISMA2012) / International Conference On Uncertainty In Structural Dynamics (USD2012). - 9789073802896 ; , s. 4193-4200
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Konferensbidrag (refereegranskat)abstract
- A modelling approach for studying waves in elastic and poro-elastic cylinders with spatially varying anisotropy is proposed. The formulation utilizes a spatial Fourier expansion for the azimuthal angle is used for the Hooke's tensor and the dependent variables. This causes the orthogonality of the modes to break down, and the modes will, sometimes to a very high degree, spread. The special case of anisotropic media having principal directions coinciding with a Cartesian coordinate system is studied, and the degree of mode spreading is discussed.
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