Ae105c CDR, June 3, 2009 p. 1

Ae105c Term ProjectCDR

Team report from

Experimental TeamJason CerundoloVivek ViswanathanPelayo Bohorquez

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Level 2 Requirements

Level 2 – Experimental Team Specific Provide experimental data, including geometry, material property, static, and dynamic data, used to verify a structural finite element model (FEM).

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Interfaces

•Will be put into master matrix in appropriate spots.

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Assumptions

All tests must be non-destructive. Filters on hardware electronics do not affect data in region of interest. – Verified by manufacturers' datasheets. The filter

cut-off frequency is much higher than region of interest.

Motion of boundary condition is negligible. – Valid assumption because motion of canister during

testing was below the noise floor. The boom's response is in the linear stress-strain region. – This is driven by the System ID and Structural teams'

models and influences experiments that are run and the processing of the data.

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Synopsis up to PDR

Geometry and material properties measurements were completed and published.

Static test were completed and in process of being published and processed.

Brainstormed ideas for dynamic testing

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Disposition of RFAs

RFA / Concern Recommendation Action Taken

#2: Address resolution of measurements

Look at specs for lasers and requirement for precision

Measurements from lasers are accurate to about 1 μm. Precision required by other teams was not specified and assumed to be sufficient.

#6: Interfaces not aligned

Teams meet to scrub interfaces

Met with teams, specifically System ID and Structural, and clarified experiments to be completed.

#7: Level 1,2 requirements not set

Specify level 1 and 2 requirements

Met as a class and determined level 1 and 2 requirements for each team.

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Progress Since PDR

Static test parameters have been published Dynamic testing completed

Random vibration Sine sweep Tap Test Ambient Test Torsion Test

Experimental descriptions, parameters, and data posted online and linked to from the wiki.

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Technical Status

All testing and publishing is completed. Experimental results have met or exceeded the requirements of the other teams.

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General Experimental Setup

Canister firmly mounted on pipe structure with racketed tie-down straps.

Laser displacement sensors measure vertical and horizontal displacement.

Shaker is attached to center of endplate. – The shaker moves a given displacement

for a given input voltage using feedback.

– A load cell measures the force applied by the shaker.

– Low load cell measurements imply modes. Signals from sensors are processed by input boxes and captured on a PC running LabView under Windows Vista.

Tests run multiple times to ensure repeatability.

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General Experimental Setup

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Static Force-Displacement Test

• Known masses were hung by the center of the end plate.

• Deflection of the boom at multiple points was measured.

• Force-displacement curve could be fit to stiffness.

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Random Vibration Test

• Shaker is given random noise from function generator.

• Data was not used in analysis – The function

generator excited up through 50 MHz.

– Region of interest was 1 – 100 Hz, only a small amount of energy was exciting those frequencies.

– This resulted in an insufficient signal-to-noise ratio.

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Sine Sweep Test

• Shaker is sine wave input swept through a frequency range (5 – 100 Hz).

• Time scale was logarithmic and around 4 octaves/minute.

• FFT of displacement over FFT of load cell data show modes of vibration.

• Mode found near 15 Hz.

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Tap Test

• Structure is excited by a manual tap with a hammer.

• The ring down response is measured. – Allows easy

calculation of damping.

– Ideally shows fundamental mode.

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Ambient Test

• Structure is left undisturbed and response measured.

• This test gives a good indication of the noises environment in the lab.

• Can identify unexpected modes and identify regions of noise.

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Torsion Test

• Shaker was mounted off-axis and connected to one of the longerons not on the vertical axis of symmetry

• Lasers were positioned off-axis.– Difference in

position is the torsion.

• Mode found near 50 Hz.

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Open Issues and Concerns

Random noise test has insufficient signal-to-noise ratio.

– FFT of ambient matched random noise. – Compensated by sine sweep testing. – Recommend a narrow band-limited function

generator to supply random noise in the future. • Current set up is limited to 50 MHz. • Region of interest is only up to 1 kHz.

Test Conducted with imperfect boundary condition.

– Recommend detailed study of canister mount be conducted in the future.

– Recommend a more isolating mount be used. Tap Test

– Force hammer would provide more data and allow for another check of results.

– For now, only good for damping

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Summary

Testing specified by level 2 requirements is complete. Geometry and material property

Provided at sufficient fidelity to Structural Team Static

Force-displacement– Used to correlate with Structural Team's model.

Dynamic Random vibration

– Used to identify regions of interest and rough estimates of mode frequencies.

Sine sweep– Chosen over random noise due to higher signal-to-noise ratio. – Used by System ID Team to correlate modes with computerized

models. Ambient noise

– Used by System ID Team to remove lab environment noise from other tests.

– Improved fidelity of data from other dynamic tests. Tap response

– Used by System ID Team to deduce damping response. Torsion

– Used by System ID Team to identify torsional modes and correlate with computerized models.

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Back-up Material

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Equipment Used

Equipment Manufacturer Model Notes

Laser Head KeyenceLK-G157 & LK-G87

Displacement sensor

Laser Controller

Keyence LK-GD500

Signal Generator

Agilent 33250AGenerate input signal for force shaker

Power Amplifier Labworks Inc. PA-138

Force Sensor PCB 208C01 a.k.a. “Load Cell”

Vibration Motor Labworks Inc. ET-132 a.k.a. “Shaker”

Signal Conditioner

PCB 480E09

Analog to Digital Converter

National Instruments

NI USB-6210

Data Collection Program

National Instruments

LabView 8.6Running on Windows Vista

Post Processing MATLab 2009bRunning on various operating systems