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An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement
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An Introduction to Scanning Laser Vibrometry for Non-Contact Vibration Measurement

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Learn about Polytec’s non-intrusive and highly productive vibration measurement technology for automated multi-point scanning of structures. The webinar will explain its application to aerospace, …

Learn about Polytec’s non-intrusive and highly productive vibration measurement technology for automated multi-point scanning of structures. The webinar will explain its application to aerospace, automotive, civil, biological, medical and micro- structures.

Topics Include:
- Concept and theory of 1D and 3D scanning vibrometry
- Technical advantages and limitations
- Productivity benefits
- Example applications including FEM validation, modal analysis, acoustics, NVH troubleshooting, automated 3D data acquisition with RoboVib and strain measurement

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  • Unlike accelerometer data, the PSV data is starting to actually look like FEM data, but is MORE accurate.
  • There are many issues with traditional contacting accelerometers, the most important of which are listed here.
  • Accel data can easily be misleading, resulting in data you think is accurate but in fact is not.
  • Operational Deflection Shape
  • 2 ref channels per shaker, 4 uncorrelated signals for shakers
  • This is a solid model of a cast aluminum transmission case that was tested with accelerometers and with the RoboVib.
  • A finite element model was generated with about 20000 nodes and 69000 elements.
  • ….we obtained the following data at 579.7 Hz…
  • Extracting the X, Y, Z amplitude and phase spectrum for each scan point ……………
  • We were able to use modal analysis software to perform curve fitting and extract the modes
  • As you can see from this slide the MAC values from RoboVib are quite respectable – certainly when compared to the accelerometer data, which was all less than 0.64
  • This resulted in a model update using the experimentally derived data. Density was changed by 1.3% and elastic modulus by 5.7%.
  • Transcript

    1. An Introduction to Scanning LaserVibrometry for Non-Contact Vibration Measurement #1
    2. Presentation Outline Deflection Shape and Experimental Modal Analysis used in the product development cycle Traditional test methods versus Scanning laser vibrometry Principles of 1-D and 3-D laser vibrometry Applications examples Accessories Conclusions #2
    3. Why Can’t We Rely 100% on the Computer Model? Uncertainties in:  Material properties  Tolerances in manufacturing Impossible or Difficult to Model:  Complex joint dynamics  Damping  Boundary conditions  Changes in stiffness during rotation → → → FEM Validation and Updating #3
    4. PSV-500-3D 16.04.2013 # 4# 4
    5. Other Examples of the Need to Perform an Experimental Modal Test Troubleshooting:  Build an experimental model  Compute structural modifications Benchmarking:  Understand the dynamics of a structure (of a competitor for example) for which we do not have a finite element model #5
    6. Full Field - Traditional Approach Issues with Contact Transducers Mass loading  Damping and stiffness errors Time consuming Limited working environments Complicated cabling Safety Coarse spatial resolution Coordinate correlation to FEM geometry cumbersome Transducer calibration Limited bandwidth Poor Modal Assurance Criteria #6
    7. A Better Solution Scanning Laser Vibrometer  Laser has no mass  Faster - laser can be scanned  Long standoffs, through windows, fluids, hi temps  No cabling on structure  Spot dia typically 10s of µm  FEM geometry import for easy point definition  One (3) transducer(s) to calibrate (no book keeping)  Wide bandwidth – no accel rolloff or resonance - to 1.2GHz!!  Reduced chance of spatial aliasing #7
    8. Spatial Aliasing 19 MP 3.00E-08 2.00E-08 1.00E-08 514 Hz 0.00E+00 68 55 42 29 6 41 7 3 6 9 -1.00E-08 15 89 92 43 94 46 61 76 91 56 06 07 04 53 01 23 18 13 08 .0 04 .0 .1 .1 .2 -0 -2.00E-08 0. 0. 0. 0. -0 -0 -0 -0 19 points 0. -3.00E-08 -4.00E-08 9 MP Low point density: 3.00E-08 2.00E-08 amplitude error 1.00E-08 0.00E+00 distorted shape -1.00E-08 0.23467 0.1619 0.08913 0.01636 -0.05641 -0.12918 -0.20195 -2.00E-08 -3.00E-08 9 points -4.00E-08 5 MP 1.00E-08 5.00E-09 0.00E+00 0.234668 0.113385 0.0163594 -0.104923 -0.201949 -5.00E-0919 point profile -1.00E-08 -1.50E-08 5 points -2.00E-08 #8
    9. Polytec Scanning Vibrometer (PSV) PSV Configurations1D Scanning 3D Scanning Simple structures Complex structures ODS Structural Dynamics Acoustics – noise source Modal analysis identification FEM validation Rotating Stress & strain Robot-integrated 16.04.2013 # 9# 9
    10. 1-D Scanning Vibrometry (PSV) Test Object Sensor Head Test Object Scan HD Electronics Video LDV Scanning Sensor Mirrors Front-end Data Management SystemUp to 250,000 locations scanned point-by-point – vibration velocity or displacementSoftware for exciter signal generation, dataacquisition, display & manipulationGeometry file imported or measured Stitched dataAnimated data visualizationData export for modal analysis or FEMvalidation # 10
    11. PSV Operational StepsOperational steps: Define measurement points using video image and draw program by geometry import Excite structure using internal or external function generator signal Scan to acquire vibration response at each point time history or FFT spectrum Visualize animated operating deflection shapes at selected frequencies of interest time domain animations Export for post-processing (e.g. modal analysis or FEM validation) # 11
    12. PSV Working Principle Scan signal Ref signalMeasure V and at many points relative to a reference signal   Amplitude and relative phase at each scan point   Spatial vibration pattern of measurement surface # 12
    13. Operating Deflection Shapes # 13
    14. Wide Ranging Applications # 14
    15. Typical 1-D Scanning Vibrometer  PSV-500-H  4 (or 8) channel data acquisition with 80 kHz bandwidth  4 or 8 reference channels  50° x 40° scan angle  13 velocity ranges up to 10 m/s  Resolution to <0.01 µm/s/√Hz  Autofocus  MIMO with multi-shaker excitation, 4 independent generator channels; Principal Component Analysis  Ethernet connection to DMS  Coherence Optimizer # 15
    16. New Technology - New Quality Digital Broadband Decoder Example measurement on black loudspeaker cone 480 pm deflection 1775 Hz 8 averages 16.04.2013 # 16 16 #
    17. Scan Modes Frequency FFT Frequency Zoom FFT Time Domain Time FastScan Time # 17
    18. Time Domain Animations # 18
    19. Configuration Examples Acoustics Acoustics Configuration 50 kHz vibrometer bandwidth digital 7 or 10 measurement ranges 1 channel for reference sensor (digital) VibroLink Ethernet connection Optional signal generator Geometry Scan Unit optional Software for acoustic measurements – live or stored data – headphones include 16.04.2013 # 19 19 #
    20. PSV-500 and its Applications Requirements for Quiet Products Sound propagation From source to receiver Transmission (structure-borne noise) F Leakage (airborne noise) Secondary noise (structure-borne noise) Operating Structural Surface Sound Emission Load dynamics velocity pressure Fluid- structure- coupling Courtesy : P. Zeller; Handbuch Fahrzeugakustik 16.04.2013 # 20 20 #
    21. Limitations of a 1-D Scanning Vibrometer Laser vibrometers measure vibration in laser direction only Data needs careful interpretation due to different vibration directions, surface shape and varying scan angles Modal analysis software expects 3-D data FE models produce 3-D data Laser Test Object Vibrometer Θ # 21
    22. 3-D Scanning Laser Vibrometry # 22
    23. Principles of 3-D Laser Vibrometry 3-D object coordinate system defined by means of a minimum of 3 known reference points Laser beam unit vectors for all scan heads are determined using the transformation matrix: 1 y vx l1x l1 y l1z v1 z vy l2 x l2 y l2 z v2 vz l3 x l3 y l3 z v3 x # 23
    24. Principles of 3-D Laser Vibrometry If the object geometry is known, all 3 lasers intersect for all (accessible) scan points 3 simultaneously acquired vibration signals are transformed into the object„s coordinate system by software y z x # 24
    25. Options for Obtaining Geometry FileData import (via UFF): a) Other test software packages b) Finite Element Model Geometry File c) Extracted from other methods such as CAT scan What if there is no geometry file? # 25
    26. Options for Obtaining Geometry FileWhen there is no geometry file: a) Alignment of all 3 laser beams manually for every scan point b) Measure geometry for every scan point GEOMETRY SCAN UNIT # 26
    27. PSV-500 Geometry Scan Unit More compact, more stable, no moving parts, faster For eg: 844 points in 3mins 30secs Higher sensitivity and wider optical dynamic range Handles larger range of surfaces and variations in surface finish # 27
    28. Beam Positioning AccuracyReasons for poor overlap: standard Inaccurate “3D-Alignment” during set up procedure Imperfect geometry dataWhy must beams overlap? with triangulation Lasers must measure at same point for optimal lateral during scan resolution More critical for strain measurements - geometry must be known for transformation to in-plane and out-of-plane data # 28
    29. PSV-S-TRIA Video TriangulationModifies the 3D coordinates by overlapping the3 beams at one point.Result: Impoved geometry as input data L forstrain calculation m [ ] L mResult: accurate geometry # 29
    30. Video Triangulation during Scan PSV-S-TRIA before triangulation # 30
    31. Video Triangulation during Scan PSV-S-TRIA after triangulation # 31
    32. Configuration Examples Structural Dynamics (3D) 3D Structural Dynamics Configuration 100 kHz vibrometer bandwidth (digital) 13 measuring ranges 8 reference channels (integrated) MIMO with multi-shaker excitation up to 4 shakers (integrated) Principal Component Analysis (PCA) Geometry Scan Unit Coherence Optimizer VibroLink Ethernet connection StrainProcessor optional 16.04.2013 # 32 32 #
    33. Station Wagon 3-D Vibration DataDeflection shape at 82 Hz showing individual measurement points # 33
    34. Benefits of Scanning Vibrometry for Modal Analysis Faster set-up  According to a European car manufacturer just the mounting and cabling of the accels and dummy masses plus the coordinate definitions for a car body usually takes around 4 – 5 days FEM mesh (coarsened) can be imported  Manual identification of points relative to FEM nodes not necessary  All points correlate exactly with FE model Faster data acquisition  No moving of dummy masses, accels and retesting Spatially more detailed data  Important for FEM correlation, model updating, and acoustics Benefits compared to Accelerometers  Insensitive to crosstalk when rotational vibration is present  Calibration not affected by temperature  Flat frequency response Software is easy to learn and system easy to use Other time savings for design (FEM) department  No modeling of dummy masses necessary A major European car manufacturer estimates total time savings of > 50% # 34
    35. RoboVib CAE workflow# 35
    36. Results Exampledeflection shape at 38 Hz # 37
    37. Case Study – Transmission Case # 38
    38. Case Study – Finite Element Model Element type Tetrahedral (solid 185) Number of nodes 19994 Number of elements 69019 Material Aluminum casting alloy # 39
    39. Case Study – Polytec Data Results Example: deflection shape at 592 Hz # 40
    40. Case Study – Test Data Frequency Response Functions # 41
    41. Case Study – Curve Fitting Circle Fitting Resonant Frequency Damping # 42
    42. Case Study – Polytec MAC Data Accel Data < 0.64 # 43
    43. Case Study – Model Update Density (% Change) = -1.3 % Elasticity Modulus (% Change) = -5.7 % Frequency ShiftAmplitude (dB) EMA Frequency (Hz) # 44
    44. Traditional - Fixed CostsAerospace GVT Example Large Size  >400 Channels  2-8 Reference Channels (MIMO) Medium Size  100-400 Channels  2 Reference Channels (MIMO) Small Size  <100 Channels  1 or 2 Reference Channels # 45
    45. Total Cost of Modal Test  Add in the variable cost of personnel on a daily rate  Add in time delay, impacts on production schedule! $$$Time &Complexity Small Medium Large Number of Channels # 46
    46. Many Accessories Enable New Applications Rotating Structures # 47
    47. Bladed Disk: 10,900 rpm 725 Hz 800 Hz 845 Hz 895 Hz # 48
    48. Many Accessories Enable New Applications Small parts at high spatial resolution, high frequencies, strain # 49
    49. Dynamic Stress and StrainStress distribution across the surface of a turbine blade in the X direction # 50
    50. FEA / Experimental Correlation Strain in x direction PSV data Strain in y direction PSV data Shear Strain PSV data # 51 Results courtesy of the University of Adelaide ME Department
    51. Many Accessories Enable New Applications Entomology Brake squeal studies # 52
    52. Conclusions More comprehensive vibration testing in a fraction of the time and effort with enhanced detail and accuracy compared to traditional techniques easily integrated with CAE/FEM FE Model Validations can be made using non-contact 3-D (and 1-D) laser measurement Many accessories are available to extend the range of applications Engineering services and rentals are available # 53
    53. Engineering Services and Rental Program Advanced non-contact vibration and surface metrology measurements available for every budget Measurements using Polytec‟s latest, non-contact measurement technology Skilled and experienced applications engineers to operate the measurement system to its fullest potential Convenience of testing at the customer‟s facility or in a Polytec lab Short-notice, critical measurements Scheduled, occasional measurements Build justification prior to purchase Save cost by renting instead of buying Budget flexibility, rent-to-buy # 54

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