Identification of Aging Aircraft Electrical Wiring Woolrich Engineering
- Slides: 38
Identification of Aging Aircraft Electrical Wiring Woolrich Engineering Consulting Firm (“Identification of Aging Aircraft Electrical Wiring, ” December 2002) Group Members: Robert Beremand Chad Hanak Melissa Straubel Sponsors: Dr. R. O. Stearman Marcus Kruger
Overview History of the Problem Theory Project Objectives Experimental Setup Lab Aging Age Analysis Recommendations
History of the Problem Faulty electrical wiring – Chafing and cracking insulation – Electrical fires – Arcing Solutions – Visual inspection Impractical – Triboelectric response May indicate condition of wire History Theory Objectives Experimental Setup Aging Age Analysis Recommendations (“Identification of Aging Aircraft Electrical Wiring, ” December 2002)
Triboelectric Effect Static Electricity – 2 materials slide against each other Frictional force causes charge imbalance History Theory Objectives Experimental Setup Aging Age Analysis Recommendations (“Identification of Aging Aircraft Electrical Wiring, ” December 2002) Induced current – Unwanted noise and interference Magnitude dependent on numerous factors
Project Objectives History Theory Objectives Laboratory Aging – Simulate aging through: Temperature & humidity – Hot and cold Jet-A fuel Saltwater solution Temperature cycling Combination of all – Visual/Touch inspection Experimental Setup Aging Age Analysis Recommendations – Did not complete
Project Objectives Age Analysis History Theory – Does age influence triboelectric effect? – Determine signal response to inputs – Relate age to measured triboelectric response – Vibration Wire Current Objectives Experimental Setup Aging Age Analysis Recommendations – More successful
Alpha Wire Specimen Kapton – Too expensive – Hard to obtain Alpha Wire 1632 (Alpha 1632) History Theory Objectives Experimental Setup Aging Age Analysis Recommendations – – 20 Gauge (thick) Stranded, Tinned Copper Rubber Insulation Low temperature tolerance o o -30 to 90 C – Majority of testing was conducted on this type of wire
Test Setup HP Signal Analyzer software & DAS – means of interpreting signal and its response – Wanted to use IDEAS, bug in software Fixed sinusoidal vibration – determine triboelectric response at fixed frequency of wires of different ages Signal Analyzer History DAS Amplifier Shaker Stinger Theory Objectives Experimental Setup Aging Age Analysis Recommendations Wire Circuit Chessboard
Test Setup Stinger – transmit vibration from shaker to platform Chessboard – platform on which wire circuit was mounted History Theory Objectives Experimental Setup Aging Age Analysis Recommendations
Test Setup – Vertical vs. Horizontal Vertical – First used checkerboardprevious group – Structure is straight No loop antenna – More wire in contact with shaker surface (gravity) Horizontal History Theory Objectives Experimental Setup Aging Age Analysis Recommendations – Grounded metal encasement to provide shielding from EMI – Strut – Longer stinger possible More distance between shaker and platform – One dimensional motion (Horizontal test setup)
Wire Tension and Twisting New wire – tendency to untwist – Varied tension Did notice real benefit to twisting new wire Consistent tension needed – – – History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Response varied with tension – can’t see trends Mean decreased as tension increased Standard deviation decreased even more Difficult to achieve uniform tension from wire to wire – Consequently, most test were conducted with the wire under no tension – Could change with better test setup
Wire Orientation History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Improve consistency Orientation of wire on checkerboard appeared to affect amplitude of triboelectric response Affixed plastic hooks to board to insure uniform orientation of wire from test to test (Wire orientation)
Examination of Twisting Dispute over effect of twisting on EMI and Triboelectric Effect – Connections and Current Flow Parallel and Series History Theory Objectives Experimental Setup Aging Age Analysis Recommendations
Laboratory Aging Temperature and Humidity – Previous success with heat alone Go hotter – – – Add Cold Test Temperature Cycles, Temperature Extremes Limited previous results from humidity alone Combine temperature and humidity exposure Freezing and Thawing – Tension test ? Corrosives – Jet-A fuel Soak History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Visually obvious effects in previous work, swelling – Saltwater Soak – Residue Effects? Graphite lubricant Combination Cycle
Aging: 10 x The Data Previous Cycle Remove 1 Sample at a Time Aging Process History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Test Sample and Do Not Return it New Cycle Aging Process Remove all 10 Samples Return Samples to Aging Process Test Samples
Aging Equipment Kitchen Ovens – Can’t run continuously Drying Ovens – Remove humidity Incubators – Most don’t get hot enough Environmental Chambers History Theory Objectives Experimental Setup Aging Age Analysis Recommendations – – Large temperature range Humidity Control Programmable Too expensive (A Bluem Environmental Chamber) (Courtesy of www. lunaire. com)
Aging Equipment Zoology to the rescue? – Old Incubator Humidity control Adequate heat ? Working condition FREE (eventually? ) History Theory Objectives Experimental Setup (The Zoology Building) (Courtesy of www. utexas. edu) – Old Freezer No humidity control Needs cleaning FREE (eventually? ) Aging Age Analysis Recommendations (The Freezer)
Anticipated Results Material characteristics should change – – History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Texture Coefficient of Friction Capacitance Resistance Changes should be reflected in the triboelectric response, and are expected to follow a detectable pattern.
Age Analysis History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Dispersed test setup components over large area to reduce Electro-Magnetic Interference (EMI) Attempted to verify repeatability with test setup Tested various sets of artificially aged wires to look for age-dependent trends in their triboelectric responses Separately enclosed shaker and test platform in grounded foil to further reduce EMI Arrived at some conclusions about test setup
Anticipated Results Shaker/Wire Test Setup: • E = portion of energy output by shaker that is transmitted to wire through friction L V dx • V = V(d. E/dt, M 1, M 2) Wire R History Theory Objectives Experimental Setup Aging Age Analysis Recommendations • E = f(σhoop)(2πr. L)µk|dx| Shaker where M 1, M 2 are material properties • We expect to find an empirical formula that describes how V changes with age
Statistical Overview Fall 2002 group concluded triboelectric response amplitudes were random. Wire History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Response to 1 KHz, 100 m. V sinusoid input (m. V) Nominal 1 2. 116 0. 142 0. 677 0. 131 1. 928 Nominal 2 0. 738 0. 145 2. 355 0. 222 0. 432 Humidity 1 (3. 5 days) 1. 970 Humidity 5 (17. 5 days) 2. 063 Humidity 10 (35 days) 1. 720
Statistical Overview History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Hypothesis: points are not random, but centered about a fixed mean with a large variance (σ2) Attempted to experimentally determine mean and σ2 values to see if trends existed Each wire specimen was tested 15 times to provide sets of data to analyze Sample mean, σ2, and accuracy of the sample mean were calculated for each wire
Statistical Overview Sample mean: Sample variance: Prediction of true mean: History Theory Objectives Experimental Setup where is the t-estimator, is the degrees of freedom, and is the accuracy percentage Aging Age Analysis Recommendations Source: Figliola, R. S. , and Beasley, D. E. Theory and Design for Mechanical Measurements. John Wiley & Sons, Inc. , New York, 2000. Pgs. 121 -125.
Verifying Repeatability History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Three new, untwisted wire specimens of the same length were tested (15 tests each) The wires were cut from different spools, and the test setup was shutdown and restarted before each wire was tested The wires were removed from the checkerboard and replaced in the same orientation between each individual test The results verify the test setup’s ability to reproduce results
Verifying Repeatability History Theory Objectives Experimental Setup Aging Age Analysis Recommendations
Test Results Overview – Retested wires from Fall 2002 that were aged in Saltwater and Jet-A Fuel No statistically significant trends History Theory Objectives Experimental Setup Aging Age Analysis Recommendations – Tested five wire samples that were aged at high temperatures in a conventional oven Inconclusive; needs more data points
Jet-A Fuel-Aged Wires History Theory Objectives Experimental Setup Aging Age Analysis Recommendations
Oven-Aged Wires History Theory Objectives Experimental Setup Aging Age Analysis Recommendations
Recent Discoveries Grand majority of signal being measured was, in fact, EMI – Had thought that EMI was a significant, yet constant contributor to the measured response signal – Results show fluctuations in response signal are of the correct order of magnitude History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Coaxial cable that was used for most measurements was determined to be partially bad – Adds noise to signal that’s of the same order of magnitude as the triboelectric response signal
Background Noise w/out Wire Attached (No Excitation) History Theory Objectives Experimental Setup Aging Age Analysis Recommendations (This doesn’t change when the system is excited at 1 k. Hz by the shaker. )
Background Noise w/ Wire Attached (No Excitation) History Theory Objectives Experimental Setup Aging Age Analysis Recommendations
Bare Wire Response (No Insulation) History Theory Objectives Experimental Setup Aging Age Analysis Recommendations
Insulated Wire Response History Theory Objectives Experimental Setup Aging Age Analysis Recommendations
Recommendations Refurbish aging equipment – Have freezer inspected by UT – Get technician from Labline to examine incubator History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Attempt further eliminate noise and/or amplify Tribo Tension Crank
Recommendations Buy EMF meter to determine what EMI remains in testing area (specifically, inside the foil enclosure) Use bare wire as control – Differential amplifier History Theory Objectives Experimental Setup Aging Age Analysis Recommendations Acquire used wire from aviation scrap yard in Dallas – Scheduling conflicts prevented this from happening this semester
Recommendations Use HP control program to capture response signal for a specified time and output to Matlab file – Could then do better statistical analysis on data and possibly cancel out ambient noise Learn new version of Ideas Frequency Response History Theory Objectives Experimental Setup Aging Age Analysis Recommendations – Load Cell – Amplifier Phase Lag Verify our conclusions with EMI-reduced setup Follow our outline for ageing process
Conclusion History of the Problem Theory Project Objectives Experimental Setup Lab Aging Age Analysis Recommendations
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