| 1. |
- Gibanica, Mladen, 1988, et al.
(författare)
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Experimental-Analytical Dynamic Substructuring of Ampair Testbed: A State-Space Approach
- 2014
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Ingår i: Conference Proceedings of the Society for Experimental Mechanics Series. - Cham : Springer International Publishing. - 2191-5644 .- 2191-5652. ; 1, s. 1-14
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Konferensbidrag (refereegranskat)abstract
- The Society for Experimental Mechanics (SEM) Substructuring Focus Group has initiated a research project in experimental dynamic substructuring using the Ampair 600W wind turbine as a testbed. In this paper, experimental as well as analytical models of the blades of said wind turbine are coupled to analytical models of its brackets. The focus is on a state-space based substructuring method designed specifically for experimental-analytical dynamic substructuring. It is shown a) theoretically that the state-space method gives equivalent results to the second order methods under certain conditions, b) that the state-space method numerically produces results equivalent to those of a well-known frequency-based substructuring technique when the same experimental models are used for the two methods and c) that the state-space synthesis procedure can be translated to the general framework given by De Klerk et al.
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| 2. |
- Liljerehn, Anders, 1979, et al.
(författare)
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Dynamic substructuring in metal cutting machine chatter
- 2010
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Ingår i: Proceedings of ISMA2010 International Conference on Noise and Vibration Engineering Including USD2010, Leuven, 20-22 September 2010. - 9789073802872
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Konferensbidrag (refereegranskat)abstract
- In metal cutting, spindle speed optimization for process stability is one example of action that may reduceproduction time and increase process reliability. For process stability, it is crucial to avoid regenerativevibrations and thereby enable larger cutting depth, with higher material removal rate as benefit. A spindlespeed optimization is usually based on the machine tool and cutting tool assembly’s frequency response atthe tool-tip. This is normally obtained by dynamic testing of the full assembly. In this paper we use areceptance coupling technique to reduce testing time by synthesizing the frequency response displacementfunction of the system. The method utilizes test data of the machine tool with an inserted blank tooltogether with a finite element representation of the real cutting tool. The coupling is made via a state spacecoupling technique. Comparisons are made with data from full system tests and a stability prediction isdemonstrated.
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| 3. |
- Gibanica, Mladen, 1988, et al.
(författare)
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Experimental-Analytical Dynamic Substructuring
- 2013
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Ingår i: Svenska Mekanikdagar, 12-14 juni, Lund, 2013 (1 page abstract). ; , s. 143-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Gibanica, Mladen, 1988, et al.
(författare)
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Spread in Modal Data Obtained From Wind Turbine Blade Testing
- 2014
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Ingår i: Topics in Experimental Dynamic Substructuring, Conference Proceedings of the Society for Experimental Mechanics Series. - New York, NY : Springer New York. - 9781461465409 ; 2, s. 207-215
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Konferensbidrag (refereegranskat)abstract
- This paper presents a pre-study for an on-going research project in experimental dynamic substructuring, initiated by the SEM Substructures Focus Group. The focus group has selected a small wind turbine, the Ampair 600W, to serve as test bed for the studies. The turbine blades are considered in this study. A total of twelve blades have been tested for modal properties in a free-free configuration. The data has been acquired and analysed by students participating in the undergraduate course ”Structural Dynamics - Model Validation” at Chalmers University of Technology. Each blade was tested by different students as part of their required course work to account for spread in modal properties between the blades. A subset of the blades weretested independently multiple times to account for variability in the test setup. Furthermore, correlation analysis of test data was made with Finite Element model eigensolution data of the blade.
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| 5. |
- Goryashko, Vitaliy, 1982-, et al.
(författare)
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Proposal for Design and Test of a 352 MHz Spoke RF Source
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- More than a dozen of spoke resonators prototypes (SSR, DSR, TSR) have been constructed and tested worldwide. None have accelerated beam until now and the ESS LINAC will be the first accelerator to operate with spoke cavities. Experience with other types of superconducting cavities indicates that high-power test is vital for reliable operation of the cavity in an accelerator. Although characteristics of a bare cavity can be obtained in a low-power test some important features of a `dressed' cavity like the electroacoustic stability and tuning system can be studied only in a high-power test stand. The ESS LINAC is a pulsed machine and the Lorentz detuning originating from the electromagnetic pressure on the cavity walls is expected to be strong. The Lorentz force along with the cavity sensitivity to mechanical excitations at some resonant frequencies may lead to self-sustained mechanical vibrations which make cavity operation dicult. Practical experience shows that increasing the boundary stiness will decrease the static Lorentz force detuning but not necessarily the dynamic one. Therefore, the FREIA group at Uppsala University is building a high-power test stand able to study performance of the ESS spoke cavity at high power. The RF test stand will be able to drive the cavity not only in the self-excitation mode but also with closed RF loop and fixed frequency. The later technique will be used to reproduce the shape of the cavity voltage pulse as it is expected to be in the cavity operating in the ESS LINAC such that the cavity tuning compensation system will be tested under realistic conditions.
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| 6. |
- 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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| 7. |
- Johansson, Anders, 1982
(författare)
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Dynamic response reconstruction using passive components
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In many testing applications within the field of structural dynamics, such as noise and vibration harshness, rattle and squeak, or durability testing in the automotive and truck industries, large hydraulic or electromagnetic actuators are used to excite the tested structure. Such actuators are mounted in the laboratory in a fixed configuration referred to here as a test rig.A frequent method for calculating the input to such test rigs is to replicate a certain reference signal, for instance dynamic responses from driving tests, to ensure that the test case is physically motivated. Versions of the Time Waveform Replication (TWR) method are often used to this end, iteratively calculating an input sequence used to excite a system such that its response replicates a desired reference. The TWR algorithm essentially estimates the unknown input by pseudo-inversion of the frequency domain transfer function.In most situations, TWR will ensure a test output which is close to the reference signal; however, if there are eigenmodes of the test specimen in the desired frequency range of the test which are uncontrollable, it can be shown that the required input force and/or the error between test output and desired reference will be large. Such problems remain even when reference-contributing modes are but marginally controllable. In a test rig such as described above, this controllability shortcoming may be impossible to prevent in the usual manner, \emph{i.e.} through changing the input configuration. This can cause poor reference replication whereby the validity of the test may be put into question.For such specific cases, where the possibilities of changing the input configuration is slim and controllability is lacking, a different approach is required. This thesis presents such an approach. It introduces the concept of passive control to the problem of response reconstruction: By attaching a modifying component to the tested structure, designed specifically to improve response reconstruction, the controllability of the system can improve.Two methods for designing such passive components are described. The first uses a high-quality finite element model of the tested structure and parameterized passive component, performing synthetic TWR experiments to evaluate its rig control properties. The second uses instead an experimentally derived model of the tested structure, which is coupled to the analytical model of the passive component through an experimental/analytical substructuring technique.
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| 8. |
- Johansson, Anders, 1982, et al.
(författare)
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Improving test rig performance using passive components
- 2012
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Ingår i: Conference Proceedings of the Society for Experimental Mechanics Series. - New York, NY : Springer New York. - 2191-5644 .- 2191-5652. - 9781461424185 ; 6, s. 437-442
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Konferensbidrag (refereegranskat)abstract
- The Time Waveform Replication (TWR) algorithm is presently used in industry for calculating the input force needed to replicate reference sensor outputs in a dynamic test rig. The feasible range of that input force is restricted by power supply and forcing rate limitations. If the force transfer paths of the reference test cannot be replicated in the test rig, lack of state controllability may cause unnecessarily large input forces and an increased remaining output error. We advocate the use of passive components to improve output tracking and limit input force demands of dynamic test rigs in the case that controllability is lacking. A method for introducing such passive components is described in this paper. It uses a virtual testing model of the test system with genetic algorithm optimization and TWR in the loop to calculate the position and dynamic properties of the proposed passive component.
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| 9. |
- Johansson, Anders, 1982, et al.
(författare)
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Improving the TWR algorithm using passive control components
- 2011
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Ingår i: Svenska Mekanikdagar 13-15 juni 2011 Chalmers Göteborg (T. Abrahmsson, A. Boström, L. Davidson, W. Kropp, H. Nilsson, K. Runesson, U. Stigh, eds.). ; , s. 11-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Johansson, Anders, 1982, et al.
(författare)
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Model calibration and uncertainty of A600 wind turbine blades
- 2014
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Ingår i: Model Validation and Uncertainty Quantification, Volume 3. - Cham : Springer. - 2191-5644 .- 2191-5652. - 9783319045511 ; , s. 215-227
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Konferensbidrag (refereegranskat)abstract
- Recently, a lot of work has been made on modeling, testing and calibrating Ampair 600W wind turbine blades, owing to the use of that turbine as a test bed structure for the Dynamic Substructuring Focus Group within the Society of Experimental Mechanics. In Sweden alone, more than 20 blades have been tested for dynamical properties, geometrical differences and material properties as was presented in several papers at IMAC XXXI. The quantity of blades, originating from different manufacturing batches, makes them ideal for investigations of component variability.In this paper, measurement variability predominantly stemming from the difference between individual blades is propagated backwards to model parameters, using model calibration techniques, in an effort to quantify their uncertainties. The coupling between spread in structural properties such as mass, center of gravity together with blade twist angles and spread in the resulting blade dynamics is shown.
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