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

1. www.polytec.com · © Polytec 1
Structural Testing Using Scanning Vibrometry
Technology Seminar

2. www.polytec.com · © Polytec 2
 Software Improvements
 Optical derotator
 Stress/Strain measurement using LDVs
 Ultra-long range vibrometer system
 Automated Robot-based testing
Outline

3. www.polytec.com · © Polytec 3
Vibrometer Types
Single Point
Scanning
3 Axis
Scanning
3 Axis
Differential
Long Range

4. www.polytec.com · © Polytec 4
Interferometer
Camera
Steering Mirrors
Important: In order to calculate deflection shapes,
a fixed phase reference needs to be established
for every scanned measurement point.
Scanning Head
Test Object
Principle of Scanning Vibrometry

5. www.polytec.com · © Polytec 5
 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
x
y z
Principles of 3D Vibrometry

6. www.polytec.com · © Polytec 6
1D Scanning
Simple Structures
 ODS
 Acoustics – noise source identification
 Rotating
3D Scanning
Complex Structures
 Structural dynamics
 Modal analysis
 FEM validation
 Stress & strain
 Robot-integrated
1D or 3D Scanning?

7. www.polytec.com · © Polytec 10
Optical Derotator
Video 1
Video 2

8. www.polytec.com · © Polytec 11
Strain Measurement Using PSV-3D

9. www.polytec.com · © Polytec 12
Strain – Case Study
-~ 2000 Points (6000 DOF)
- Points of FE Grid
- Video Triangulation
- Overlaps the lasers
- Provides accurately measured geometry

10. www.polytec.com · © Polytec 14
Strain – Case Study
ODS Strain

11. www.polytec.com · © Polytec 15
Example: deflection shape at 580 Hz
Case Study – FE  Experimental

12. www.polytec.com · © Polytec 16
Removing Uncertainty

13. www.polytec.com · © Polytec 18
MAC Result
Accelerometer Data < 0.64

14. www.polytec.com · © Polytec 19
FE Model Validation – Bridging the Gap
Amplitude(dB)
Frequency (Hz)
Frequency Shift
Density (% Change) = -1.3 %
Elastic Modulus (% Change) = -5.7 %
EMA

15. www.polytec.com · © Polytec 20
Sound Field Characterization
 Traditionally done with
microphone arrays
 Applications: TPA, Noise Source
Identification
 Measure vibration on an optically
reflective and acoustically
transparent membrane
Acoustics Studies with LDVs
Source: Laboratoire Vibrations Acoustique, France

16. www.polytec.com · © Polytec 21
Sound Source Characterization
 Change in refractive index
appears as change in normal
velocity
 Laser beam reflects from a rigid
surface
 Every measurement point gives
information on sound distribution
 Time domain animation provides
wave propagation information
Acoustics Studies with LDVs
Source: Andy Harland, Loughborough University
Discrete
Points on
Target
Laser
Source
Acoustic
Source
x
zy
Acoustic
Field

17. www.polytec.com · © Polytec 22
Power Distribution
 Obtained from power spectrum at
acoustic frequencies of interest
 Applications: source
characterization and identification;
hydrophone calibration; sound
intensity measurement; material
characterization; speakers,
distance sensors
Acoustics Studies with LDVs
Source: Andy Harland, Loughborough University
10 mm

18. www.polytec.com · © Polytec 24
RSV-150 long range laser vibrometer
 Bridge height 108m
 Steel framework
 Distance > 140m
 Excitation: train
displacement of the
bridge during slow
pass-by of train
Single Point Solutions

19. www.polytec.com · © Polytec 25
3D Scanning Vibrometry - RoboVib

20. www.polytec.com · © Polytec 26
Automated Data Acquisition
Scanning VibrometerRobot
Continue
Stop at pre-defined
positions
Scan
Start
(TCP/IP)
RoboVib – Workflow

21. www.polytec.com · © Polytec 27
Fully Automated Robot-Assisted 3-D

22. www.polytec.com · © Polytec 28