Space Flight Cable Properties and Cable Response

Test Plan

Kaitlin SpakFeb 17, 2013

Test Set Up Constants• Cable length: 8” buffer, 10” test section, 8” buffer• Tie down snugness: Level 5 (very tight) at outer ends always, level 5 at inner

connections also• Excitation: White noise at 0.1 V from signal generator, amplifier to max to provide 0.3

V• Tensioned wire length and tension: length at 24 cm, still evaluating ways to confirm

equivalent tension; upon further thought, tension in cable should be taken into account by dynamic force gauge. As long as cable is not largely bent due to wire tension (can be checked with laser displacement system), slight tension variations should not have an effect. DC Offset kept at mid level, bending of cable less than 1 mm.

• Driving point at 3.25” from bottom of 10” test section• Position of cable 60” from vibrometer, <5 deg angle spread, midpoint approximately

at cable center• Targets at every 0.37” for scans (27 points over 10”, density of 50 on Polytec software),

target at driving point for single point data (scans for mode shapes, DP for comparison and frequencies)

• Tension of cable is uniform- pulled by mass of 2 pounds and then zip tied to maintain tension (added after preliminary H type cable testing)

“Standard” Set Up

• 8” buffers, 10” test section• 24 cm wire at mid DC offset, slight tension• White Noise 0.1 V amped to 0.3 V• Tight 525 Zip Ties• 2 lbs cable tension• Cable oriented with curve toward shaker

• Polytec Point data file names:Date_Cable_Excitation_Cable Section_Variation from

Standard_Run Number.pvd

Suspended shaker with tensioned wire to load cell on cable

Buffer section- tightly pinned at top and bottom

Test section, 10” with targets every half inch and target on DP

Buffer section, 8”

Tie down inputs- at right angles to shaker input, tie down attached to TC105 tabs glued onto Bosch structure

Driving point attachment; tensioned string (Spectrex 150 lb P Line fishing line from Honeywell Spectra line) to swivel glued in screw to load cell to aluminum block via threaded stud to TC105 tab to zip tie to cable. Should provide only lateral force input, no moment.

Vibrometer Software Settings

• FFT measurement, 30 complex averages per point (no appreciable change after 25)

• References include impact hammer, load cell, signal generator, and stationary laser. Load cell used as primary reference, channel 3.

• 5 kHz low pass filter• VD-08 10 mm/s/V• Bandwidth of 2 kHz, looking at 0-500 Hz to start, interesting

information appears to be largely between 0 and 250 Hz• 6400 FFT lines, 50% overlap, Hanning window for white noise

excitation, rectangular window for burst random or hammer impact

Excitation Parameters

• White Noise• 0.1 V on software• Amped at max to 0.3 V

• Random excitation with Hanning window to reduce leakage

• Could use burst excitation with triggers, but seems to take longer for no appreciable improvement in clarity/frequencies… will show this conclusively as part B of Test 1

Equipment Parameters

• Load cell: PCB 208C01 SN22703Calibration: 112.9 mV/NEquates to 8.857396 N/V as Polytec ICP input

(Read as 112.4 mV/N, used 8.896 N/V for test 1 until Mar 6 Test 1A runs 3-5. Difference minimal.)

• Impact Hammer: PCB 086C01 SN 22469Calibration: 11.2 mV/NEquates to 89.285714 N/V as Polytec ICP input

• Cable ties: Ty-Rap TY525M cable ties

TEST ONE: Variation of Parameters/ Sensitivity Analysis

• Uses a single 1X19 H-type cable measured at driving point• A) Compare five sections of 1 by 19 tied and wrapped cable• B) Compare different excitation methods: hammer test, burst

random excitation (Triggered), white noise excitation• C) Tension in stinger string varied, length varied • D) Tension in cable varied: 1 lb, 2 lb, 3 lb, 4 lb, hand tight, slack.• E) “Loose” (setting two) zip tie versus “tight” zip tie (setting

five) compared to show the effect; small ties also compared• Intended to show which parameters have greatest effect and

what needs to be maintained from test to test• Length will remain constant at 10” test sectionResults to be presented at SDM in Boston in April

Test 1 Records

• Feb 20 -22: First round of tests on H type cables, several sections

• Feb 25: Revised test plan• Feb 26: Ran first set of A type cable• Feb 27: Ran second set A type cable• Feb 28: Ran third set A type cable• Mar 4: Ran fourth set A type cable• Mar 5: Ran fifth set A type cable• Mar 6: Ran test 1A for five cable sections (runs 3-5 with

corrected calibration) • Mar7-11: Evaluation of Test 1 Data

TEST TWO: Data Collection on Cables for Statistical Analysis

• To present at SDM April conference (at least data collection… should be able to compare to Timoshenko DTFM model with calculated cable parameters at least)

• For cables: wire gauge, jacketing and type will remain the same, variables will be number and arrangement of wires and possibly lay angle

• Start with 3-5 sections each of 1X7, 1X19, 1X49 and 7X7 cables, 28” long, made VERY carefully!

• If time later, vary lay angles for one/each of these (ambitious!)• Using the four different different cables,( all other parameters the

same and as identical in tests as possible) get M,C,K data, apply statistical analysis

• This is the main body of work; testing will likely take 2 or 3 iterations.

TEST THREE: Cable Parameters/GHM Data

• To be incorporated in “Shear Beam” paper• Attempt to determine cable parameters to

incorporate into model• Use Instron/DMA to apply force at a specific

frequency, measure effect on stiffness/cable parameters

• Determine GHM parameters*• Will refine this test upon completion of tests 1

and 2, approximately beginning of April

TEST FOUR: Effect of Bakeout on Space Cables

• To be presented at SEM June conference• Take cables, test them, then bake them out and retest. • Requires coordination with bakeout people to include a

few cables in one of their existing bakeouts. Would have to be really careful with recreation of end conditions and test conditions in general.

• Can run concurrently with test 2 if needed, must be completed by May.

• Could also do these with the Instron/DMA…?

Timeline: Feb/Mar

• February 19-21: Finalize test set up, answer all test set up questions, get Matlab codes working perfectly to process data, talk to cable constructors/get wire to make cables

• February 25-Mar 6: Test 1, Sensitivity Analysis• Mar 7-10: Evaluate Test 1, modify test 2 if needed• Mar 10 – Mar 31: Test 2- make cables, gather

cables, test cables, multiple runs for several types• Mar 19: SDM paper due

Timeline: April

• April 1-4: Prepare ROUGH prelim presentation, VSGC paper

• (April 4-11): Boston SDM Conference, present paper

• April 12-16: Set up and run test 3, Look at test 3 data, fit to GHM, work on model

• April 17: NASA Technology Showcase (Wash. DC)• April 18: VSGC conference (Norfolk, VA)• April 22-May 1:Continue with test 3

Timeline: May

• Early May: Prepare and conduct test 4 with bakeout cables, write up test 4 results for SEM

• Mid May: Revisit tests 1, 2 if additional data needed• Early-mid May: Prepare prelim presentation• May 21: Preliminary examination• Complete any remaining testing, work on modeling

and statistical analysis, more advanced models.• Note that timeline is ambitious and subject to

change!