Vibration Acoustics Laboratory Laboratoire Festival Vibrations-Acoustique. Golden Head park

Transcription

1 Vibration Acoustics Laboratory Laboratoire Festival Vibrations-Acoustique of light Golden Head park

2 Staff: 4 professors +1 open position 6 assistant professors 2 engineers 1 technician 2 secretaries 9 PhD students 8 Masters students Key research areas: Sound transmission and radiation Mid-frequency modelling Source identification / characterisation Sound perception Hot topics: Time reversal Mems S t Nizier

3 Sound transmission and radiation Modelling of sound radiation Fluid / structure coupling Acoustic transparency of panels Active control of sound transmission Mid-frequency modelling Improved SEA Hybrid modelling Energy mobility Intensity potential approach Source identification / characterisation Inverse methods in vibro-acoustics Sources of vibration and pressure pulsation Vibration and acoustic sub-structuring Vibration diagnosis / acoustical holography Sound perception Subjective assessment of industry noise Coupling between vibratory and acoustic stimuli Structural parameters versus noise perception Preference Models

4 Direct industrial funding Cars (Renault, PSA, Volvo trucks), Aeronautics (Airbus), Navy (DCNS,DGA), Buildings (Lafarge, St Gobain) Mems (CEA Leti) Public funding: Rhône-Alpes Region National Predit programme EU PCRD programme Carnot Institute City hall

5 Using Structures as Sensors for source Characterization Saint Jean

6 Arts Museum Summary Introduction The RIFF method: basic examples Regularization The RIFF method with lost information The RIFF method: using the weak formulation Application to turbulent boundary layer excitation Perspectives and Conclusion

7 Introduction Is it possible to use the structure vibrations to measure the external boundary pressure?

8 Basic example of Beam Bending Vibrations ( ) x 4 2 EIρSω wx w( x) = F x 4 ( ) F ( x) 4 wx ( ) = EρSω I 4 x 2 wx ( ) ( ) F= EI i w + + w w Δ 2 4 i+ 2 wi+ 1 wi wi 1 i 2 ρsω i 5 vibration points 1Force point

9 Basic example of Plate Bending Vibrations Eh 3 2 ( ν ) 12 1 w w w x y x y ρhω w= F ( x,y) ( ) F x,y = Eh ( ν ) w w w x y x y ρhω w

10 Force distribution Calculated Vibration field

11 What happens when measurement uncertainties are considered? Calculated Vibration field with simulated uncertainty (1% of noise) 1 Force distribution

12 Regularization technique Art of illusion Trompe l oeil

13 Regularization Measurement points (j,i) { } { } L W = F ji, i j

14 Tikhonov regularization min L ji, { F } { } { } j W + α F i j To select an optimum regularization parameter : a graphical tool, the L curve. { F } 2 j Optimum parameter 1 L ji, { } { } 2 Fj Wi

15 Regularized Force distribution Calculated Vibration field with simulated uncertainty (1% of noise)

16 The RIFF method with lost information

17 Lost information, example of cylinders

18 Lost information, problem of cylinders Above ring frequency Below ring frequency

19 The RIFF method: using the weak formulation

20 Using the weak formulation

21 Using the weak formulation to obtain boundary shear force Choosing a particular test function

22 Using the weak formulation to obtain boundary shear force Choosing a particular test function

23 Experimental Validation Shear force A B Force sensor RIFF Identification C 0.6 Laser vibrometer 0.4 shaker Fréquency(Hz) A : Limit due to integration length C: limit due to the measurement mesh No regularization is needed!

24 Taking into account uncorrelated excitations Jacquart Loom

25 Taking into account uncorrelated excitations Mechanical link G i correlated forces uncorrelated forces Lumière brothers

26 Experimental results Micro flash mount RIFF

27 perspectives 1) Force distribution measurement using an Aray of microflowns sensor Nostradamus 2) Use RIFF technique with finite element model to identify internal sources in machinery or engines: large number of mesh points necessitate condensing the FE model (Craig-Bampton)

28 perspectives Nostradamus 3) Use piezoelectric materials with adapted shape to calculate the weak formulation integral giving the shear force, the bending moment, the displacement,..

29 perspectives 4) Detecting structural defects as anti forces' Nostradamus

30 perspectives Scanned Substructure Reference accelerometer 3 added masses Scanning Laser Vibrometer Frequency: 1603 Hz Measured Velocities are injected in a FEModel with dynamic condensation of rotations Tikhonov regularisation coupled to L- curve criteria 30

31 Results (3/6) Results with no regularisation 1603 Hz Identified Forces L-curve (green circle denotes chosen regularisation parameter) 31

32 Results (4/6) Results undersmoothed 1603 Hz Identified Forces L-curve (green circle denotes chosen regularisation parameter) 32

33 Results (5/6) Results before optimal regularisation 1603 Hz Identified Forces L-curve (green circle denotes chosen regularisation parameter) 33

34 Results (6/6) Results oversmoothed 1603 Hz Identified Forces L-curve (green circle denotes chosen regularisation parameter) 34