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Dynamics of Rotating Structures Relealed
 

Dynamics of Rotating Structures Relealed

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Learn how dynamic torsional motion found in rotating bodies can be measured using non-contact angular velocity and displacement sensors. Controlling torsional vibrations is critical to designing ...

Learn how dynamic torsional motion found in rotating bodies can be measured using non-contact angular velocity and displacement sensors. Controlling torsional vibrations is critical to designing reliable vehicles, electric power generators and aircraft propulsion systems.
Rotational vibration data, used in the early stages of product development, has enabled design and test engineers to reduce noise, vibration felt by the passenger/operator, and to substantially increase durability. Classic examples of products with dynamic torsional motion are: drive shafts, universal joints, CV joints, electric motors, combustion engines, turbines, pumps, gearboxes / transfer cases.
Discover how vibrometers can be used to measure the vibration at fixed points and scanned to characterize the entire surface even when the structure is rotating.
Our experts in the field of vibrometry will be on hand to answer any questions you have about your current and future measurement needs and requirements.

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    Dynamics of Rotating Structures Relealed Dynamics of Rotating Structures Relealed Presentation Transcript

    • Dynamics of Rotating Structures Revealed Using Non-Contact Laser Vibrometers 8/24/2012
    • Presentation OutlineRotationalvibrations  Technology behind rotational vibrometer  Why use lasers?  Application examplesDerotation  Derotator  Description  Derotated measurements 8/24/2012
    • Vibration in Rotating ObjectsVibrations in horizontal, vertical and axial planesare easy to measure with a single point sensor 8/24/2012
    • Vibration in Rotating ObjectsAs shafts transmit power they createand are subjected to torsional vibrations 8/24/2012
    • Goal – Find critical resonances – Map operational deflection shapes – Verify finite element simulationsUnder real operational conditionsWithout altering the data! 8/24/2012
    • The Contact Approach: EncodersDisadvantage : – requires mounting on shaft end – instrumentation time – Location is fixed – Changes moment of inertia pulley adaptor encoder 8/24/2012
    • Vibration in Rotating ObjectsRotational pulses are due to changes in angularvelocity, and must be measured with a rotationalvibrometer. 8/24/2012
    • RLV-5500 Rotational VibrometerConsists of – Optical Sensor Head (RLV-500) Compact Contains two Laser Doppler Interferometers IP67 protection – Demodulation Electronics (RLV-5000) 8/24/2012
    • Rotational Vibrometer Dual Beam Sensor HeadIntegrated meter shows centerline balanceand light return signal strength 8/24/2012
    • Aligning Lasers with Shaft Balance Indicator: Symmetric Asymmetric One SidedThe measurement result is independent of the alignment, however,asymmetry reduces the rpm measurement range. 8/24/2012
    • Rotational VibrometerThe shape of the object is irrelevant,and the measurement is insensitive to any lateral vibrations. 8/24/2012
    • Rotational Vibrometerf DA = 2V A λ Doppler Frequency Beam A V A = ω R A cos αf DB = 2VB λ Doppler Frequency Beam B V B = ω R B cos β d = RA cos(α) + RB cos(β) f D = 2d ω fDλ f D = f DA + f DB => ω = λ 2d 8/24/2012
    • Rotational Vibrometer fDλ ω = 2d From the equation you can see that the rotational velocity ω is only dependant on: - λ (laser wavelength) - f D (measured) - d (beam separation) The radius, lateral position, out-of-plane and in-plane shaft vibrations are automatically cancelled out of the equation therefore:  The measurement is insensitive to any lateral vibrations in x, y or z  The measurement is insensitive to shape of object 8/24/2012
    • Signal Processing Angular Velocity Angular Displacement RPMDC and AC components are separated from one anotherComplete separate decoding for RPM and dynamic componentVery small angular vibrations can be detected even at high RPMDisplacement is integrated velocity signal 8/24/2012
    • Advantages• No special fixtures or prepared surfaces• Shaft doesn’t have to be machined or even round• Has a dual interferometer = better sensitivity• Displays RPM without linear speed or radius info• Switch turns rotational vibrometer into a single pointvibrometer• Contains a Bragg cell allowing measurement ofpositive and negative rotations as well as vibrationsaround zero RPM 8/24/2012
    • Sample Applications Measurement of Rotational Vibrations on: – Crank Shafts – Drive Shafts – Clutches – CV / Universal Joints – Optimization of Tuned Mass Damper – Paper and Printing webs Ramp Up – Ramp Down Characterizations: – Crank Shafts – Electric Motors – Coupled Machine Components 8/24/2012
    • Belt Pulley of Crankshaft Single Point Vibrometer: Axial VibrationsRotational Vibrometer: Rotational Vibrations 8/24/2012
    • Crankshaft Results 2 4 6 8 Engine Running Speed Frequency Spectrum 8/24/2012
    • Crankshaft Results Order Spectrum of the Rotational Vibrations 8/24/2012
    • Drive Shaft ApplicationsDrive Shaft Torsional Response 8/24/2012
    • Drive Shaft (Order Analysis) Applications Constant Velocity Joint Universal Joint TorsionsDrive Shaft Torsional Response 8/24/2012
    • Drive Train Testing Measure events on high-dynamic dynamometers 8/24/2012
    • Drive Train Testing Dual Mass FlywheelTwo flywheel masses that are linked by elastic springs 8/24/2012
    • Drive Train Testing Dual Mass Flywheel Results 8/24/2012
    • Supercharger Order AnalysisIf orders excited with too high of an amplitude, failures can occurVery small hub requires non-contact method 8/24/2012
    • Application: Pump ShaftTorsional vibration limit related to pump failure 8/24/2012
    • Application: RPM Ramp Test on Clutch Dyno Absorber Drive 1/RPM signal Data RLV-500 Acquisition ∆ϖ 8/24/2012
    • Drivability Motor CycleTuning torsionalvibration dampers – test crank shaft vibration under driving conditions measurement with crank shaft adapter Source: InFocus 2008/2 courtesy BMW Group 8/24/2012
    • Performing Linear MeasurementsWith two beams anytranslational movement iscanceled out in the signalWhen terminating one beamwith a mirror, linearmovements can be detected 8/24/2012
    • Performing Linear Measurements RLV-500In the “II” position two beams are emitted and the unit is in rotationalmode.In the “I” position one beam is emitted and the unit is in single pointmode.In the “0” position both beams are shut off 8/24/2012
    • Accessories90 degree deflectionAir Wipe 8/24/2012
    • Measurement Specifications (7.5 mm beam)RPM Measurement: – Range: from -8,000 to +20,000 rpm – Analog Output: -4V …+10V – Error: <0.3%Angular Velocity Measurement – Range: from << 10°/s/V up to 6,000°/s/V – Frequency Range: 0.5Hz to 10kHz – High pass and low pass filters, order and variable band pass filtersAngular Displacement Measurement – Measurement Range: 0.01°/V, 0.1°/V, 1°/V – Analog Output: + 10V – Frequency: 1 Hz up to 10 kHz 8/24/2012
    • Measurement Specifications (24 mm beam)RPM Measurement: – Range: from -2,500 to +6,500 rpm – Analog Output: -2.5V …+6.5V – Error: <0.3%Angular Velocity Measurement – Range: from << 10°/s/V up to 12,000°/s/V – Frequency Range: 0.5Hz to 10kHz – High pass and low pass filters, order and variable band pass filtersAngular Displacement Measurement – Measurement Range: 0.01°/V, 0.1°/V, 1°/V – Analog Output: + 10V – Frequency: 1 Hz up to 10 kHz 8/24/2012
    • FeaturesBandwidth – (0) 0.5 Hz – 10 kHz – 30th order at max. speedResolution – 0.01 °/s = 0.00017 rad/s – sufficient for • combustion engines and gears • gas turbines (special mode for constant speed) • pumps • printers – limitation • steam turbines require 100 x resolution 8/24/2012
    • Rotating the RLV Sensor Head If we reduce the beam separation either side of the rotational axis from d to d‘, we gain RPM range: d‘=d * cos Υ d d Rotating the sensor head and reducing the beam separation (d‘) allows us to not only measure higher rpm‘s but also on smaller shafts. 8/24/2012
    • Scanning Vibrometer PrincipleExample: piezo motor MP1 MP2 MP3 ... sequential measurement at all points. video image object meas. points in video image Excitation for all points spectrum MPn phase referencegrid after measurement deflection shape @ 36kHz spectrum MPn+a 8/24/2012
    • Drive Train Vibrationsscanning at fixed rpm along shaft – bending modes are visible 20 Hz 262 Hz 8/24/2012
    • Measurements on rotating partsAxial measurement on tireDeflection shape of rotating tireat 50 mph 8/24/2012
    • Measurements on rotating partsRadial measurement on tireDeflection shape of rotating tire at 16 mph – Scan area limited by speed on circumference 8/24/2012
    • Decoder saturationRadial measurements Tangent. velocity r sensor vtangent = ωr Radial velocity +v 0 vtangential t -v Time-signal 8/24/2012
    • Measuring Rotating Structures –The Goals:Measure under real operating conditionsTrack deflection shapes rotating withstructure to avoid smearing of dataAvoid the drawbacks of telemetry and/or slipringsAnd…..Can we achieve all of this while enjoying thebenefits of laser vibrometry? 8/24/2012 # 41
    • Vacuum Pump Counterweight • Failing during operation • Strain not predicted • Vibrometer revealed • 9th order of rotation excites bending @ ~3875 rpm • Deflection shape • FE model updated • Part redesigned 8/24/2012
    • PSV-A-440 Optical Derotator • Scanning Laser Vibrometer – ODS • Single Point Laser – Phase reference • Object speed – Max. 24,000 rpm • Acceleration – Max. 700 rpm/s • For Order Analysis • Scan angle – Max. +/- 4° 8/24/2012
    • Reference LDV Adjustable (OFV-505, IVS, PDV) mirror for reference LDV positioning Derotator unit PSV Scan head Adjustable base (for Co-axial unit for alignment of rotating reference LDV axis) Derotator Controller for motorized controller telescopic driveVertical telescopic drive Base frame 8/24/2012
    • Shift of Resonances During Run-up • Curved plot of Eigen resonances – Stiffening ofRPM material – Centrifugal forces – Excited by orders Frequency – Important for composites and plastics 8/24/2012
    • Run-up and shift of resonances actual resonance at order calculated resonance eigenfrequency at standstill 8/24/2012
    • Bladed Disk: 10900 rpm 8/24/2012
    • Bladed Disk: 10900 rpm 725 Hz 800 Hz 845 Hz 895 Hz 8/24/2012
    • ApplicationsElectronic industry – Noise reduction in cooling systems for consumer products, trouble shootingAerospace – Durability and FE update on blisk and fansAutomobil – Cooling fans – Tires – Turbo Chargers (@ reduced rpm levels) 8/24/2012
    • Benefits of Vibrometry with OpticalDerotation• Whole field measured…..stress analysis, modalanalysis, FEM validation• Acquire reliable FEM validation data under realoperating conditions• Obtain operating deflection shapes rotating withstructure• No added mass, change in flow dynamics• No potentially noisy telemetry or slip rings 8/24/2012
    • ConclusionOptical vibration measurement – reduces limitations – avoids mass loading and added moment of inertia – allows assessment of resonances of • shafts (torsional and bending) • axial measurements of rotation objects – fans, tires .. – Optical Derotation delivers • order analysis • operational deflection shapes 8/24/2012
    • Engineering Services and Rental ProgramAdvanced 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 8/24/2012