Penn State Center for Acoustics and Vibration

Transcription

1 Penn State Center for Acoustics and Vibration Structural Vibration and Acoustics Group Presented as part of the 2010 Spring workshop Stephen Hambric, Group Leader Marty Trethewey Stephen Conlon Liming Chang Tim McDevitt Tony Jun Huang Sabih Hayek Eric Mockensturm Gary Gray Kevin Koudela Fabio Semperlotti

2 Overview NASA Gearbox Noise Effects of bearings on noise transmission Student Research Fluid film bearing impedances (J.H. Gyurko) Phononic Crystals and Acoustic Bandgaps and Mirages (Sz-Chin S. Lin) Sound Intensity in Reverberant Environments (A. Barnard) Sound transmission through joints between spacecraft structures (B. Grisso, A. Barnard, M. Shepherd) 2/33

3 Rotorcraft Transmission Noise Path Model, Including Distributed Fluid Film Bearing Impedance Modeling Investigators: S.A. Hambric, E. Smith, R. Bill, A. Hanford, R. Campbell Students: M. Shepherd Sponsor: 3/33

4 NASA GRC s Test Gearbox Receiver: Panel vibrations, and subsequent sound radiation Source: gear mesh transmission error Transmission Path: through bearings 4/33

5 Project Goals Develop steady state, timeharmonic FE/BE approach for simulating gear mesh noise transmission through bearings and housings Bearing types: Rolling element Traditional fluid-film (journal) NASA s wave bearings (modified journal) Validate against measurements taken in NASA-GRC s test rig 5/33

6 Measurements vs. Simulations Simulated Measured n=4 n=3 n=2 6/33

7 Measurements vs. Simulations Mode shape Mode Simulated shape frequency Simulated Measuredfrequency Measuredfrequency Loss factor Loss factor (1,1) (1,1) 465 Hz 465 Hz Hz 489 Hz 489 Hz Hz (2,1) (2,1) 864 Hz 864 Hz Hz 876 Hz 876 Hz Hz (1,2) (1,2) 1215 Hz 1215 Hz Hz1223 Hz 1223 Hz Hz (3,1) (3,1) 1532 Hz 1532 Hz Hz1555 Hz 1555 Hz Hz (3,2) (3,2) 2279 Hz 2279 Hz Hz2232 Hz 2232 Hz Hz (4,1) (4,1) 2400 Hz 2400 Hz Hz2546 Hz 2546 Hz Hz Mode shape Simulated frequency Measuredfrequency Loss factor (1,1) (1,1)(2,1) (1,2) (2,1) 465 Hz (1,2) (3,1) (3,2) (3,1) 489 Hz (3,2) (4,1).061 (4,1) (2,1) 864 Hz 876 Hz.061 (1,2) 1215 Hz 1223 Hz.044 (3,1) 1532 Hz 1555 Hz.048 (3,2) 2279 Hz 2232 Hz.053 (4,1) 2400 Hz 2546 Hz.012 (1,1) (2,1) (1,2) (3,1) (3,2) (4,1) 1 2 Drive locations input output 7/33

8 Stiffnes (N/mm) Damipng (N-s/mm) Journal and Wave Bearings Penn State software simulates bearing stiffnesses and damping 800, , ,000 Wave 3,000 2, ,000 2,000 Journal 400,000 1, ,000 Roller 1,000 Wave 200, ,000 Journal Ball RPM RPM Ball/roller bearing damping: N/mm/s per Kraus et. al., ASME JVA, 109, , /33

9 Radiated Sound Differences output input 9/33

10 Measuring Impedances of Journal Bearing Films Advisors: S.A. Hambric and K.M. Reichard Researcher: J. Harrison Gyurko (Ph.D. Acoustics pending) Sponsor: ARL Penn State 10/33

11 Goals Measure distributed stiffness and damping of fluid film in a journal bearing Verify simulation codes Fluid Film Bearing Schematic x m y C C xx yx C C xy yy x y Conventional Lumped Mass Coefficients K K xx yx K K xy yy x y F F x y 11/33

12 Test Rig Pair of shakers drives bearing vertically or horizontally Oil feed Proximity probes measure bearing displacement Pressure transducers Journal bearing test setup Cross section of test bearing assembly 12/33

13 Results Stiffnesses (Sommerfield number of 0.13) 13/33

14 Results Damping (Sommerfield number of 0.13) 14/33

15 Phononic Crystals and Acoustic Bandgaps and Mirages Advisor: T.J. Huang (support also provided by Bernhard Tittmann) Researcher: Sz-Chin Steven Lin (Ph.D. ESM pending) 15/33

16 angular frequency ω What are Phononic Crystals? Inspired by field of photonics, and the reflection and refraction of light Periodic elastic media 1D 2D 3D Bragg s law bandgap 2asinθ = nλ nπ/asinθ wave vector k Many researchers around the world are pursuing this phenomenon 16/33

17 Applications On-chip waveguides, filters, and multiplexers Acoustic filter / switch Physical Review E 69, (2004) 17/33

18 New Concept: Gradient Indexed (GRIN) Phononic Materials Adjust sizes of inclusions, material properties, and/or filling ratios according to a specified gradient function Creates acoustic mirage effect, redirecting the sound waves 18/33

19 Articles and Next Steps Journal articles already published Applied Physics Letters 92, (2008) Physical Review B 79, (2009) Journal of Physics D: Applied Physics 42, (2009). Next steps Complete simulations and experimental verifications Complete thesis 19/33

20 Sound Intensity in Reverberant Environments Advisor: S.A. Hambric Researcher: Andrew Barnard (Ph.D. Acoustics pending) Sponsor: 20/33

21 Goals In a reverberant water tank, measure: Narrow-band radiated sound power Sound pressure directivity patterns Traditionally, can only measure the following in reverberant environments: Broad-band (usually one-third octave-band) radiated power Spatially-averaged sound pressures 21/33

22 Procedure Supersonic Intensity in Reverberant Environments (SIRE) Measured/Simulated Data SIRE Processing Pressure Particle Velocity Temporal FFT Spatial FFT Signal Separation K-space Filtering Spatial IFFT Normal Active Intensity Power Directivity Hologram Surface Normal P h, U h P 1 U 1 P 2 U 2 Acoustic wavenumber in the surrounding fluid k θ k z Supersonic structural waves 22/33

23 Elevation Normalized L W [db re 1 pw/(m 3 /s) 2 ] Elevation Dipole Source Measurements Raw Intensity SIRE Dipole Free Field Theory Radiated Acoustic Power from TC4033 Dipole Hz Raw Hz Raw SIRE SIRE Frequency [Hz] Azimuth Azimuth SIRE accurately measures radiated power as shown by comparison to free field theory. SIRE accurately measures directivity patterns. (Top: Normal Intensity, Bottom: SIRE). Notice the interference patterns in the reverberant tank prevent accurate directivity measurements in the upper figures. 23/33

24 Cylinder Results In general, raw intensity over-predicts and supersonic intensity under-predicts SIRE is within 2 db of T60 method in 1/3 octaves Evanescent nearfield effects Destructive interference 24/33

25 Structure-borne power through joints between composite and metal structures Advisors: S.A. Hambric and S.C. Conlon Researchers: Ben Grisso (Ph.D. Post-Doctoral Student) Andrew Barnard (PhD Student) Micah Shepherd (PhD Student) Sponsor: 25/33

26 Goals Help develop design procedures that minimize structure-borne sound through launch vehicle panels Measurements on coupled 4 x 7 honeycomb sandwich panels Conductances Energies Loss Factors (Internal, Radiation, and Coupling) Wavenumber processing to determine transmission coefficients 26/33

27 Test Setup Panel 2 Panel 1 27/33

28 Conductance (s/kg) Modal Measurements 1.E-01 2,0 2,1 3,0 Panels Bolted 1.E-02 5,3 1.E-03 1.E-04 1.E-05 Panel 1 average Panel 2 average 1.E-06 1.E ,000 Frequency (Hz) 28/33

29 Loss factor Loss Factors 0.1 Total Loss Factor Radiation Loss Factor 0.01 Overall loss factors converge to structural loss factors Computed using modal FRFs and Boundary Element Software Frequency (Hz) 29/33

30 Wavenumber Processing and Transmission Coefficients l y H k m ikmx ikny, k, f Hx (, y, f ) W(, x y) e e x n A( f) 1 k x m k y n Modal FRFs H kw( km, kn, foto ) k 0 0 l x Exponential windowing function k mn mn 0 y k m 2 2 : :, and kn : :. x L x y L y 0 ( ) (,, ) B1 f Hkw km kn foto k k m n x Zero padded beyond l x and l y to increase resolution k k mn mn 0 0 y ( f ) D B D1 B1 2 ( f ) D A D2 A2 2 Over all angles of incidence for now 30/33

31 Power Transmission Coefficient Example of wavenumber transform results Unfiltered Drive on panel k b dl ~ tau 1->2 Backward filtered tau 2-> Frequency (Hz) 31/33

32 Other Projects and Programs Vibration and acoustic scattering of submerged shell structures (Sabih Hayek) Composite structural acoustics (Kevin Koudela) Machine lubrication (Liming Chang) Nonlinear dynamics (Gary Gray) 32/33

33 Future Projects Requalification of reverberant chamber Andrew Orr (M.S. student in Acoustics) Patch methods for characterizing panel sound transmission characteristics Roch Scherrer (M.S. student from INSA de Lyon) 33/33