Ae105c CDR, June 3, 2009 p. 1

Experimental Team Jason Cerundolo Vivek Viswanathan Pelayo Bohorquez

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Experimental Level 2 Requirements

Provide experimental data, including geometry, material property, static, and dynamic data, used to verify a structural finite element model (FEM).

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Group Interfacing

Experimental System ID Structural Dynamics

Experimental

• Statics & dynamics test data • Experimental setup descriptions• Voltage to displacements/acceleration conversions• Experimental data in engineering units• Experimental parameters used

• Mass & Geometry• Material Properties• Test Specifications

System ID

• Deadlines to meet• Experiments to perform• Test parameters• Test procedures

• Damping Coefficients• Natural Frequencies• Static Results

• Modal shapes (for correlation)• Frequencies• Damping• Static and dynamic result

Structural• Experiments to run• Requests for properties to be measured

• Theoretical model containing the modes of the dynamical system

• Modal Properties (mass, length, etc.)

DynamicsSystem Performance project level

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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.

Battens are always in compression.

Diagonals always in tension.

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.

Longeron

Batten

Diagonal

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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

Initiator Concern Recommendation Action

MarcoAddress resolution of measurements

Look at spec of lasers and precision required

Laser precision around 1 μm and confirmed to be

sufficient by other teams.

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Progress Since PDR

Static test parameters have been published.

Dynamic testing completed. Random vibration Sine sweep Tap 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 correlated with theoretical predictions.

Special thanks to Case Branford for help in the lab.

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General Experimental Setup

Canister firmly mounted on pipe structure with ratcheted 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.

Middle Root Canister

Side Tip

Side Root

Tip

Force Shaker

Load Cell

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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.

Canister

Root

Middle

Tip

Displacement [mm]

1.95

4.9

Plot courtesy of Case Bradford

Time

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Sine Sweep Test• Shaker is given sine wave

input swept through a frequency range (5 – 100 Hz).

• Time scale was logarithmic and approximately 1 octave/minute.

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

• Modes found near 11 & 14 Hz.

Frequency [Hz]

Inte

nsi

ty r

ati

o

dis

pla

cem

ent/

forc

e

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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.

Time [s]16-0.8

0.8

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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 52 Hz.

Root Same Side of Load

Tip Opposite

Side of Load

Root Opposite Side of Load

Tip Same Side of Load

Force Shaker

Load Cell

Plot goes here

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Open Issues and Concerns

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

– Replaced 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 100 Hz.

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

• Low signal-to-noise ratio.

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

computerized models.• 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

EquipmentManufacture

rModel Notes

Laser Head KeyenceLK-G157 & LK-

G87Displacement 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

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Material Property Experiments

Diagonal Tension Test

Batten Compression Test

Batten Tension Test

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Material Property Measurements

Diagonals: cylindrical cross section

Battens: rounded rectangle cross section

Property Value [Units] Method

Length 24.9 cm Ruler

Diameter 1.25 mm Calibers

Mass 1.2 g Scale

Young’s Modulus 48.97 GPa Tensile Test

Property Value [Units] Method

Length (uncompressed) 18.1 cm Ruler

Width 2.87 mm Calibers

Depth 3.77 mm Calibers

Mass (batten unit) 14.2 g Scale

Young’s Modulus TDB Tensile Test

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Static Test Setup

4 Laser displacement sensors

DAQ unit collects data at 100 HzWeights added to the tip

Fixed boundary condition created with two tie-down straps

Tip

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Static Test Results

Time

Dis

pla

cem

ent

Dis

pla

cem

ent

Time

Tip

Canister

Root

Middle

Tip

Middle

Canister

Root

Canister

Root

Middle

Tip

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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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Random Vibration Test

• Shaker is given random noise from function generator.

• Test was unsuccessful – 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.