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Ae105c Term Project CDR Team report from Experimental Team Jason Cerundolo

Ae105c Term Project CDR Team report from Experimental Team Jason Cerundolo Vivek Viswanathan Pelayo Bohorquez. Level 2 Requirements. Level 2 – Experimental Team Specific

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Ae105c Term Project CDR Team report from Experimental Team Jason Cerundolo

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  1. Ae105c Term ProjectCDRTeam report from Experimental Team Jason Cerundolo Vivek Viswanathan Pelayo Bohorquez

  2. 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).

  3. Interfaces • Will be put into master matrix in appropriate spots.

  4. 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.

  5. 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

  6. Disposition of RFAs

  7. 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.

  8. Technical Status • All testing and publishing is completed. • Experimental results have met or exceeded the requirements of the other teams. 8

  9. 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. 9

  10. General Experimental Setup 10

  11. 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. 11

  12. 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. 12

  13. 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. 13

  14. 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. 14

  15. 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. 15

  16. 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. 16

  17. 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 17

  18. 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.

  19. Back-up Material

  20. Equipment Used

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