| 1. |
- Andersson, N., et al.
(författare)
-
Feature-based design analysis for automatic classification of simulated nonlinear responses using machine learning
- 2016
-
Ingår i: Proceedings of Isma2016 International Conference on Noise and Vibration Engineering and Usd2016 International Conference on Uncertainty in Structural Dynamics, ed. by Sas, P; Moens, D; VanDeWalle, A.. - 9789073802940 ; , s. 3259-3273
-
Konferensbidrag (refereegranskat)abstract
- A practical concept design analysis approach for automatic processing and classification of simulated responses is presented. Deterministic and nonlinear dynamics are studied under ideal loading and low noise conditions to determine fundamental system properties, how they vary and possibly interact. Responses should be classified into characteristic types, such as periodic or nonperiodic, resonant or nonresonant, linear or nonlinear, and further into subcategories such as single or dual frequency responses, hardening or softening. For this, time-signals are evaluated using methods and metrics commonly used within structural dynamics and then possibly associated with qualitative features according to measures based on a set of rules-of-thumb criteria. A support vector machine is trained to determine whether a single feature, or combinations of features, applies or not. This paper describes elements of the analysis, report practical considerations and discuss the effectiveness of evaluated features using known few-degree-of-freedom examples.
|
|
| 2. |
- Botha, J. D. M., et al.
(författare)
-
Some noise predictions for small wind turbines
- 2016
-
Ingår i: Proceedings of ISMA 2016 - International Conference on Noise and Vibration Engineering and USD2016 - International Conference on Uncertainty in Structural Dynamics. - : KU Leuven, Departement Werktuigkunde. - 9789073802940 ; , s. 4019-4032
-
Konferensbidrag (refereegranskat)abstract
- In the FP7 SWIP project three small wind turbine designs have been considered. These include two Horizontal Axis machine with a rated power of 4 and 20 kW and a 2 kW Vertical axis configuration. These will be mounted at three pilot sites with supporting atmospheric modelling and measurements. This paper presents broadband aeroacoustic noise predictions. The prediction methods compare semi empirical predictions more usually used for large turbine applications) supported where appropriate by CFD flow calculations. In order to pursue mitigation measures for these scales of machines, the noise is analysed on a component basis and considered from the viewpoints of self noise and inflow noise. The vertical axis machine is shown to dominated by boundary layer noise whereas the horizontal axis machines are more susceptible to inflow noise. In this the modelling of the inflow turbulence spectrum is seen to be critical.
|
|
| 3. |
- Chen, Yousheng, et al.
(författare)
-
Validation of a model calibration method through vibrational testing of a mechanical system with local clearance
- 2016
-
Ingår i: Proceedings of ISMA2016 International conference on noise and vibration engineering and USD2016 International conference on uncertainty in structural dynamics. - Leuven, Belgium : Katholieke University Leuven. - 9789073802940 ; , s. 2581-2595
-
Konferensbidrag (refereegranskat)abstract
- Nonlinear finite element models are often validated using experimental data. A previously proposed calibration method, which concerns pre-test planning, multi-sinusoidal excitation and an effective optimization routine, is improved with an extended version of the pre-test planning. The improved method is validated using a test structure with a clearance type nonlinearity. From the pretest planning, an optimal configuration for the data acquisition is determined. The multi-harmonic nonlinear frequency response functions (FRFs) of the structure under test are then generated by a multi-sinusoidal excitation. Model calibration is conducted by minimizing the difference between the experimental multi-harmonic nonlinear FRFs and their analytical counterparts. The uncertainties of the estimated parameters are assessed by a k-fold cross validation, which confirm that the uncertainties of the estimated parameters are small when the optimal configuration is applied.
|
|
| 4. |
- Felcsuti, G., et al.
(författare)
-
Effect of modal behaviour on dynamic transmission error of driveline gears
- 2016
-
Ingår i: Proceedings of ISMA 2016 - International Conference on Noise and Vibration Engineering and USD2016 - International Conference on Uncertainty in Structural Dynamics. - : KU Leuven, Departement Werktuigkunde. - 9789073802940 ; , s. 865-875
-
Konferensbidrag (refereegranskat)abstract
- Dynamic transmission error (DTE) is widely accepted as the source of gear whine noise, therefore its reduction is essential for NVH optimization of drivelines. While most studies in hypoid gear dynamics concentrate on the gears only, this paper takes into account the additional effect of other driveline components and examines their contribution to the DTE. The analytical model developed in this paper consists of a hypoid gear pair connected to a simple structure with well-defined modal behaviour. A test rig is specifically designed to validate the model. In the rig, the pinion rotates only along one axis while the gear is also allowed to have translational motion induced by a rigid body modes on an elastic foundation. This model could help identifying the most influential parameters in terms of the mode and DTE interaction and thereby improve the NVH performance of driveline units.
|
|
| 5. |
- Olsson, Jörgen, et al.
(författare)
-
Impact evaluation of a thin hybrid wood based joist floor
- 2016
-
Ingår i: Proceedings of ISMA 2016, presented at the International Conference on Noise andVibration Engineering (ISMA). - Leuven, Belgium : Katholieke University Leuven. - 9789073802940 ; , s. 589-602, s. 589-602
-
Konferensbidrag (refereegranskat)abstract
- The purpose of this paper is twofold. The first aim is to develop a numericalanalysis procedure, by combining FRFs from FE-models with analyticalformulas for sound emission and transmission from the ceiling anddownwards within a room with four walls. The aim is to, by applying thisapproach; accomplish a tool which calculates the relative impact soundbetween different joist floors, in the low frequency range. The second aim is tobenchmark a thin hybrid wooden based joist floor with similar thickness,surface weight and global bending stiffness as a concrete hollow core floorstructure. What will be the difference in sound transmission? The question isrelevant since it may be necessary to make thinner wood based joist floors inhigh rise buildings, if wood should stay competitive against concrete. Theresults show that the direct transmissions of impact sound are very similararound the first bending mode. As the frequency increases, the modes in thestructures differ significantly. Below 100 Hz, the concrete floor has 4 modes,while the hybrid joist floor has 9 modes. As the frequency increases the soundradiation characteristics differs. The results show that it is possible to havesimilar sound transmission properties around the first bending modes for ahybrid based joist floor and a hollow core concrete floor structure with similar thicknesses. At the first modes of the structure, the information about thesurface weight and global bending stiffness are useful for prediction of soundtransmission properties but for higher modes, they are not sufficient.
|
|
| 6. |
- Rice, H., et al.
(författare)
-
A development on fast frequency sweep methods for acoustic radiation problems
- 2016
-
Ingår i: Proceedings of ISMA 2016 - International Conference on Noise and Vibration Engineering and USD2016 - International Conference on Uncertainty in Structural Dynamics. - : KU Leuven, Departement Werktuigkunde. - 9789073802940 ; , s. 521-533
-
Konferensbidrag (refereegranskat)abstract
- The direct point by point swept solution of the discretised Helmholtz equation over a broad frequency range can become computationally expensive for large systems when fine frequency increments are required. Approaches involving reduced-order models using Padé-or waveform-based methods such as the well conditioned asymptotic waveform evaluation (WCAWE) can be used to significantly reduce this and can also be applied to systems with non-quadratic frequency dependency. In this paper WCAWE expansions are performed on a finite element based dynamical model of a two microphone open flanged impedance tube test. The use of an approximate loss-factor-based PML type approach to model the radiating section of the system is considered which eliminates dependency on reciprocal frequency terms. This allows for an efficient high order expansion as the frequency derivative terms need to be retained only up to second order. It is then shown that the method efficiently gives robust predictions of the end impedance with simple non-specialized elements.
|
|
| 7. |
- Östling, Dan, et al.
(författare)
-
Modelling and characterization of nonlinearities in a tuned mass damper-impulse hammer versus shaker excitation
- 2016
-
Ingår i: Proceedings of ISMA 2016 - International Conference on Noise and Vibration Engineering and USD2016 - International Conference on Uncertainty in Structural Dynamics. - : KU Leuven, Departement Werktuigkunde. - 9789073802940 ; , s. 3711-3719
-
Konferensbidrag (refereegranskat)abstract
- The rubber springs of a tuned mass damper (TMD) exhibit both nonlinear stiffness and damping, which complicates measurements of the frequency response function (FRF) of the device. In this paper we model and compare the frequency responses measured with both impulse hammer excitation and a shaker base excitation method. Since the impulse response will spend only a short time in the nonlinear regime, a reasonable assumption is that the nonlinearities will be less apparent and more difficult to determine. The results show that this is not the case and that both methods yield similar nonlinear parameters. By comparing responses at different excitation levels with appropriate nonlinear models, the nonlinearities can be determined. The results indicate that these approximations of the nonlinear effects are able to describe the dynamic behaviour of the TMD, and that the nonlinear properties of the material differ somewhat in the two measurement situations.
|
|
