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Mechanische trillingen

Mechanische trillingen. LES 9 – MODALE ANALYSE. Patrick Guillaume E-mail: patrick.guillaume@vub.ac.be Tel.: 02/6293566. Random Excitation. Random sequence with Gaussian distribution Random amplitudes and phases Averaging is needed Converge to flat amplitude spectrum

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Mechanische trillingen

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  1. Mechanische trillingen LES 9 – MODALE ANALYSE Patrick Guillaume E-mail: patrick.guillaume@vub.ac.be Tel.: 02/6293566 MECHANISCHE TRILLINGEN, LES 9, 2005

  2. Random Excitation • Random sequence with Gaussian distribution • Random amplitudes and phases • Averaging is needed • Converge to flat amplitude spectrum • Remark: Force is not flat in general due to interaction with the structure • Signal processing errors (leakage errors) • Effect of nonlinearities is reduced by averaging MECHANISCHE TRILLINGEN, LES 9, 2005

  3. Random Noise MECHANISCHE TRILLINGEN, LES 9, 2005

  4. Uniform Window MECHANISCHE TRILLINGEN, LES 9, 2005

  5. Hanning Window MECHANISCHE TRILLINGEN, LES 9, 2005

  6. Burst Random MECHANISCHE TRILLINGEN, LES 9, 2005

  7. Burst Random with Uniform Window MECHANISCHE TRILLINGEN, LES 9, 2005

  8. Exponential Window MECHANISCHE TRILLINGEN, LES 9, 2005

  9. Periodic Random / Pseudo-Random Excitation • Periodic random • No leakage errors (periodic signal) in steady-state conditions • Averaging is required • Pseudo random • Constant amplitudes and random phases • No leakage errors (periodic signal) in steady-state conditions • Averaging is not required MECHANISCHE TRILLINGEN, LES 9, 2005

  10. Impact Excitation • Force transducer and tip • Advantages • Easy to use • No interaction with structure • Force is flat in useful frequency range • Relatively inexpensive MECHANISCHE TRILLINGEN, LES 9, 2005

  11. Impact Excitation • Disadvantages • Large crest factor • Nonlinearities • Limited control of amplitude spectrum MECHANISCHE TRILLINGEN, LES 9, 2005

  12. Force Window • Force window (or transient window) • Remove noise • Effect of “Double Hits” MECHANISCHE TRILLINGEN, LES 9, 2005

  13. Response Window • Lightly damped structure • Leakage errors • Heavily damped structure • Remove noise MECHANISCHE TRILLINGEN, LES 9, 2005

  14. Overzicht EMA EMA = Experimentele Modale Analyse • Stap 1: Experimentele opstelling • Stap 2: Opmeten van de FRF’s • Stap 3: Bepalen van de modale parameters door bvb. curve fitting • Stap 4: Validatie van de resultaten • Stap 5: Toepassingen MECHANISCHE TRILLINGEN, LES 9, 2005

  15. Step 1: Setting Up the Modal Test • Choosing DOFs • Suspension • Choice of excitation • Position/connection of force transducer • Mounting the response transducers • Transducer conditioning and calibration • Setting up the analyzer • Range setting • Frequency band • FRF estimator MECHANISCHE TRILLINGEN, LES 9, 2005

  16. Step 2: Making the Measurements • Checking the quality of the measurements • Noise • Nonlinearities? MECHANISCHE TRILLINGEN, LES 9, 2005

  17. Rigid Body Modes MECHANISCHE TRILLINGEN, LES 9, 2005

  18. Step 3: Modal Parameter Estimation • SDOF • Uncoupled modes • MDOF • Coupled modes MECHANISCHE TRILLINGEN, LES 9, 2005

  19. Curve-Fitters for Modal Analysis – MDOF • Two step approach • Poles are global parameters • Time MDOF (LSCE) • Freq. MDOF (PolyMAX) • Mode shape vectors are local parameters • LSFD MECHANISCHE TRILLINGEN, LES 9, 2005

  20. Stabilization Diagram MECHANISCHE TRILLINGEN, LES 9, 2005

  21. Least Squares Frequency Domain – LSFD MECHANISCHE TRILLINGEN, LES 9, 2005

  22. Residual terms – LR, UR MECHANISCHE TRILLINGEN, LES 9, 2005

  23. Step 4: Checking the Model • Synthesized FRF • Modal Assurance Criteria MAC MECHANISCHE TRILLINGEN, LES 9, 2005

  24. PZL Mielec Skytruck (FLiTE Project) MECHANISCHE TRILLINGEN, LES 9, 2005

  25. Stabilization Diagrams LSCE LSCF (PolyMAX) MECHANISCHE TRILLINGEN, LES 9, 2005

  26. Mode Shapes (3.17 Hz, 1.62 %) MECHANISCHE TRILLINGEN, LES 9, 2005

  27. Mode Shapes (8.39 Hz, 1.93 %) MECHANISCHE TRILLINGEN, LES 9, 2005

  28. Computer Simulations: What if? • Modification simulation • Design optimization • Response simulation • Acoustic noise calculations • Fatigue analysis • … MECHANISCHE TRILLINGEN, LES 9, 2005

  29. Dynamic Modelling Process MECHANISCHE TRILLINGEN, LES 9, 2005

  30. FE Model Updating MECHANISCHE TRILLINGEN, LES 9, 2005

  31. Structural Dynamic Modifications MECHANISCHE TRILLINGEN, LES 9, 2005

  32. Slat Track Optimisation MECHANISCHE TRILLINGEN, LES 9, 2005

  33. Forced Response Simulation MECHANISCHE TRILLINGEN, LES 9, 2005

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