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Introduction to Vibration Qualification Testing

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A free monthly webinar hosted by ASQ Reliability Division presenting David Common on Introduction to Vibration Qualification Testing

A free monthly webinar hosted by ASQ Reliability Division presenting David Common on Introduction to Vibration Qualification Testing

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  • 1. Introduction toVibrationQualificationTestingDavid Common©2013 ASQ & Presentation Commonhttp://reliabilitycalendar.org/webinars/
  • 2. ASQ Reliability DivisionEnglish Webinar SeriesOne of the monthly webinarson topics of interest toreliability engineers.To view recorded webinar (available to ASQ ReliabilityDivision members only) visit asq.org/reliabilityTo sign up for the free and available to anyone livewebinars visit reliabilitycalendar.org and select EnglishWebinars to find links to register for upcoming eventshttp://reliabilitycalendar.org/webinars/
  • 3. Engineering, Testing, Consulting andInspection ServicesDavid CommonDynamics Testing ManagerApplied Technical Services, Inc.Marietta, GAdcommon@atslab.com(678) 444-2905May 09, 2013Introduction to Vibration Qualification Testing
  • 4. Agenda• Why should we care about vibrations ?• Where do vibrations come from ?• What are the types of vibration and how are theyanalyzed from a test lab perspective ?• How are vibrations replicated in the lab ?• In Practice• Questions?
  • 5. Why should we care about vibrations ?Although some specific applications aim at creating‘good’ vibrations (loudspeakers), most vibrationsources have the potential to create issues.
  • 6. Why should we care about vibrations ?(cont.)Issues can be of different kinds:• Functional (CD skip)• Comfort (squeak, rattle)• Structural
  • 7. Where do vibrations come from ?• Machinery• Road
  • 8. Where do vibrations come from ?• Wind load (Tacoma bridge)• Ground motion
  • 9. What are the different types of vibrations?• Sinusoidal vibration• Most basic• Simple motion• One (1) frequency present at any given time
  • 10. Sinusoidal Vibration0 10 20 30 40 50 60-1.5-1.0-0.500.51.01.5Time (ms)Acceleration(G)Acceleration WaveformCh110 1000.43.01.0Frequency (Hz)Acceleration(Gpeak)Acceleration ProfileDemandControl
  • 11. Sinusoidal Vibration0 5 10 15 20 25 30-0.8-0.6-0.4-0.200.20.40.60.8Time (sec)Acceleration(G) AccelerationDemandCh1
  • 12. Sinusoidal Vibration
  • 13. Sinusoidal Vibration - Quantification• Typically expressed as:• Acceleration vs. frequency• Velocity vs. frequency• Displacement vs. frequency• Any combination of the above vs. frequency
  • 14. • Random vibration• ‘Random’ nature due to incapacity to predictprecise vibration level at any given time• Quantified using statistical tools• Broadband, multi-frequency content• More closely match real-world excitationsWhat are the different types of vibrations?
  • 15. Random Vibration10 100 1000-61x10-51x10-41x10-31x10Frequency (Hz)AccelerationSpectralDensity(G²/Hz)Acceleration Spectral DensityDemandCh10 500 1000 1500 2000 2500 3000 3500 4000-6-4-20246Time (ms)Acceleration(G)Acceleration WaveformCh1
  • 16. Random Vibration – Really random?10 100 1000-61x10Frequency(Hz)AcDemandCh10 500 1000 1500 2000 2500 3000 3500 4000-6-4-20246Time(ms)Acceleration(G)AccelerationWaveformCh1
  • 17. Random Vibration – Kurtosis adjustment50 100-26x10-11x10Frequency(Hz)AcceleratiCh10 500 1000 1500 2000 2500 3000 3500 4000 4500 5000-60-40-200204060Time(ms)Acceleration(G)AccelerationWaveformCh1
  • 18. Random Vibration – Quantification• Expressed as PSD (‘Power Spectral Density’) or ASD(‘Acceleration Spectral Density’) vs. frequency• Dimension is g2/Hz (or (m/s2)2xs)• PSD is the random vibration level, normalized with respect tothe bandwidth of analysis (since dealing with a broadbandexcitation)• Tabulated values will sometimes have a ‘gRMS’ value added:• This is the overall energy introduced by the randomvibration profile (integrates PSD vs. frequency)
  • 19. Random Vibration – Different shapes…2001 10 100-51x10-41x10-31x10-21x10Frequency (Hz)AccelerationSpectralDensity(G²/Hz)Acceleration Spectral DensityCh10 500 1000 1500 2000 2500 3000 3500 4000 4500 5000-3-2-10123Time (ms)Acceleration(G)Acceleration WaveformCh1• Truck transportation simulation
  • 20. Random Vibration – Different shapes…• Engine compartment simulation60 100 1000-61x10-51x10-41x10-31x10-21x10Frequency (Hz)AccelerationSpectralDensity(G²/Hz)Acceleration Spectral DensityCh10 100 200 300 400 500 600 700-6-4-20246Time (ms)Acceleration(G)Acceleration WaveformCh1
  • 21. Let’s mix things up – Sine on Random• Add discreet sinusoidal vibration tones to a broadbandrandom vibration background• Typical of helicopter and propeller aircraft applications(known blade passing frequencies on a randombackground)
  • 22. Let’s mix things up – Sine on Random20 2000100 1000-41x10-31x10-21x10-11x1001x10Frequency (Hz)AccelerationSpectralDensity(G²/Hz)Acceleration Spectral DensityCh10 500 1000 1500 2000 2500 3000-10-50510Time (ms)Acceleration(G)Acceleration WaveformCh1
  • 23. Let’s mix things up – Random on Random• Add narrowband random content onto a broadbandrandom background• Typical of tracked vehicles (military)• Narrowband content is swept across a frequency rangeto reflect speed changes
  • 24. Let’s mix things up – Random on Random20 2000100 1000-41x10-31x10-21x10-11x1001x10Frequency (Hz)AccelerationSpectralDensity(G²/Hz)Acceleration Spectral DensityDemandCh10 500 1000 1500 2000 2500 3000 3500 4000-20-15-10-505101520Time (ms)Acceleration(G)Acceleration WaveformCh1
  • 25. Random vibration vs. Transients…• Traditional random vibration averages out the actualvibration history.• Transients such as bumps, potholes, etc. do not translatewell into random• Another technique is needed to replicate transients
  • 26. • Field data replication• Data collected in the field (acceleration vs. time)is directly played back and repeated in the labWhat are the different types of vibrations?
  • 27. Field data replication0 10000 20000 30000 40000 50000 60000-2-10123Time (ms)Acceleration(G)AccelerationDemand0 10000 20000 30000 40000 50000 60000-2-101234Time (ms)Displacement(in)DisplacementDemand0 10000 20000 30000 40000 50000 60000-20-10010203040Time (ms)Velocity(in/s)VelocityDemand
  • 28. How are vibrations replicated in the lab?• Shakers• Mechanical• Electrodynamic• Hydraulic• Single/Multi-axis
  • 29. How are vibrations replicated in the lab?• Mechanical shakers (‘direct drive’)• 1950’s• Cheap, sinusoidal excitation• Still used today for shipping vibration testCourtesy of Lansmont Corporation
  • 30. How are vibrations replicated in the lab?• Electrodynamic shakers• Make most of the fleet of commercial test labs• Sequential, single-axis excitation• Big, highly-controlled ‘loudspeakers’• Come in various sizes and shapes (sliptable)• Rated in lbf• Payload and severity counterbalance eachother
  • 31. Electrodynamic shakers
  • 32. Electrodynamic shakers – Combined• Shakers can becombined with thermalchambers (‘AGREE’chambers) fortemperature andvibration testing(engine-mountedcomponents might seehigh vibration levelsand extremetemperature range)
  • 33. Electrodynamic shakers• Medium to high frequency range (typically from5Hz to 2,000Hz)• Low available displacement (2” peak-to-peak)
  • 34. Electrodynamic shakers• Fun with astrobelight…
  • 35. Hydraulic shakers• Low frequency range (typically 1Hz to 100Hz)• High available displacement (10” or 12” peak-to-peak)• Often offer the highest force rating for the buck
  • 36. Hydraulic shakers• Single-axisCourtesy of Dynamic Testing and Equipment
  • 37. Hydraulic shakers (Triaxial)• Triaxial hydraulic shaker table
  • 38. Hydraulic shakers – Triaxial
  • 39. In Practice…• Fixtures…• Position of the control accelerometer…• How many control accels?• Sliptable use…
  • 40. In Practice… Fixtures
  • 41. In Practice… Fixtures
  • 42. In Practice… SliptablesCourtesy of Unholtz-Dickie Corporation
  • 43. In Practice… SliptablesCourtesy of Unholtz-Dickie Corporation
  • 44. Multiple control accelerometers - Extremal• Two control accelerometers used in an ‘Extremal’strategy
  • 45. Multiple control accelerometers - Average• Four control accelerometers used in an ‘Average’strategy
  • 46. Multiple shakers• Testing of large/heavy payloadsCourtesy of Lansmont Corporation
  • 47. Questions?• Contact info:• David Common – dcommon@atslab.com• (678) 444-2905

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