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Test Status Overview

Test Status Overview. HCAT Program Review NASA, Florida Dec 13,14, 2000. Rationale. A lot of data has been generated in HCAT/CHCAT program in the past 3 or 4 months Aim is to show overall status - where we are in testing and what we have learned overall Put current data in a logical order

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Test Status Overview

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  1. Test Status Overview HCAT Program Review NASA, Florida Dec 13,14, 2000

  2. Rationale • A lot of data has been generated in HCAT/CHCAT program in the past 3 or 4 months • Aim is to show overall status - where we are in testing and what we have learned overall • Put current data in a logical order • Address what we are doing to resolve some testing issues • Suggest some “compartments” for existing and new data

  3. Aircraft use of HVOF coatings Why are we doing this? - commercial flight tests Overall status of JTP tests JTP - Corrosion, wear, fatigue, embrittlement, impact Ancillary - Process specs, producibility, additional corrosion, additional fatigue, failure mechanisms Conditions seen by real parts Summary of findings to date What does all this mean for actual usage? Where does it work just fine? Where do we need to worry? Overview

  4. Flight testing - Why are we doing this? • Flight testing (Boeing, Delta, Lufthansa etc.) shows acceptable performance with no serious problems • Wear performance much better than chrome • no gouges, striations, flaking, etc. commonly seen in Cr • better seal life if Ra~4” (rapid seal damage if rough) • some FPI crack pattern indications on Lufthansa aft inner cylinders (Barkhausen showed no crack penetration to substrate), nothing requiring removal from service Typical chrome damage - axle

  5. Production use of HVOF WC-Co and WC-CoCr coatings

  6. Production use of HVOF WC-Co and WC-CoCr coatings (cont.) • Qualified for landing gear repair <0.010”

  7. Production use of HVOF landing gear coatings - Messier-Dowty • Note production use on high performance aircraft

  8. Data summary:Landing Gear JTP - Coupon test data

  9. Data summary:Propeller Hub JTP - Coupon test data

  10. C-HCAT B117 JTP work complete HVOF performed significantly better than chrome - Pass US-HCAT B117 Initial test results reported in Ottawa, Aug 00 HVOF coatings worse than Cr - Fail Appears to be a testing issue Corrosion • Outstanding issues - resolution of US-HCAT results • Retesting under way • Different sealing - Boeing Cd method • 2 different geometries (Flats and cylinders) • 2 different deposition conditions (Southwest Aero, Hitemco) • 2 different cabinets

  11. Embrittlement • Tests partially complete • Sequence 1 - HVOF does not cause embrittlement - Pass • Sequence 2 - Not yet complete • H2 can diffuse through HVOF coating • May need longer bake • Sequence 3 begun - no data yet • Outstanding issues • Environmental embrittlement measurements in process • Coating may lower Kt - calculations and tests under way at Heroux

  12. WC-Co US-HCAT testing complete All WC-Co air fatigue data equal to or better than Cr - Pass All WC-Co corrosion-fatigue data equal to or better than Cr - Pass Delamination from some specimens at high cycles WC-CoCr WC-CoCr 0.003” delamination at high load - Pass below 180 ksi, Fail above 180 ksi WC-CoCr 0.010” delamination at high load - Pass below 125 ksi, Fail above 125 ksi WC-CoCr corrosion-fatigue - Fail?? Fatigue - WC-Co • Not a structural issue, but a functional issue (Messier-Dowty) • Outstanding issues • Results of WC-CoCr fatigue testing • being addressed under Ancillary Testing

  13. Wear • Fretting and sliding (hydraulic) • Data evaluation largely complete • HVOF better than or equal to Cr • Rig and flight tests all show better wear performance • Less striation, wear, roughening (Delta, Greene Tweed) • Less wear and leakage of seals (Greene, Tweed)

  14. Impact • Drop ball testing • Under way • Gravelometry (Boeing) • Completed - HVOF as good as or better than Cr - Pass

  15. Data summary:Landing Gear JTP - Rig and flight testing

  16. Data summary:Propeller Hub JTP Rig and flight testing

  17. PTFE (Enercap) much better performance with WC low leakage low rod wear Elastomer rapidly damaged not a problem with long stroke utility actuators and landing gear at 4 Ra Hydraulic testing - Greene, Tweed 4-9 ” Ra

  18. Landing gear rig tests • Boeing F/A-18 E/F landing gear pins • HVOF coatings “passed” full scale rig fatigue test • darkened, but no wear damage, passed MPI • Outstanding - Additional full scale tests to be done by C-HCAT • Messier-Dowty F-18 E/F NLG fatigue • Messier-Dowty F-18 E/F drag brace fatigue • including catapult loads • BFG Dash-8/400 MLG • BFG NLG steering actuator • BFG simulated piston fatigue

  19. Flight tests • Delta B737, 757, 767 nose and main landing gear • Inner cylinders, axles, axle sleeves • Passed - WC-CoCr qualified for O&R • Boeing 767-400 • HVOF WC-CoCr flight qualified and used in production • Canadian F-18 MLG • Messier-Dowty polygon repair • WC-CoCr • Repair scheme approved • Outstanding - NADEP-JAX P3, DND C-130 testing

  20. Data summary -Ancillary tests

  21. Process parameters • WC-Co optimized by Jerry Schell by DOE methods • OO-ALC, Hitemco - JP 5000, DJ • Process designed for 8-12 Almen compressive stress • WC-CoCr optimized by Jean-Gabriel Legoux, NRC by DOE methods • DJ-gun at NRC and VacAero • Process designed for 8-12 Almen compressive stress • Coating parameters different from QPL conditions used by Southwest Aero

  22. Grinding and finishing • Overall finding - for seals need 4” or less Ra • Use fine grind or superfinish (specify other parameters?) • Low stress grinding developed by Jon Devereaux at NADEP-JAX • used on all US-HCAT samples • Surface measurement and superfinishing developed for landing gear by Jay Randolph at Delta • Testing carried out by John Falkowski (Boeing) and Jim Nuse (Southwest Aeroservice) - AESF paper • Additional testing under way • Boeing, SW Aero, Sulzer Metco, Engelhard, Praxair, Green Tweed, Supfina, Delta

  23. Stripping • Water jet does not work very well • Rochelle salt works well for WC-Co and WC-CoCr • SW Aero, Sulzer Metco • NADEP-Cherry Point, NTS • Testing at Praxair and others shows no embrittlement with strippers • No good method for T400 yet • Outstanding - need good chemical strip for Tribaloy

  24. Fluid compatibility • Under way shortly at Heroux • Will include evaluations of hydrogen embrittlement due to fluids

  25. NDI • FPI best method so far • Delta, Boeing • MPI not effective • Boeing has used Barkhausen with some success • Heroux testing begun • Outstanding - how detect cracks in substrate without removing coating?

  26. Corrosion • All HCAT generic, C-HCAT, Lufthansa data on flats shows HVOF having better performance than Cr • US-HCAT Landing gear JTP data on rods showed worse than Cr - Fail • Repeating with better edge seal - comparing sample shapes, deposition conditions, test locations • Outstanding - Resolution of poor US-HCAT test performance (under way)

  27. Fatigue and fracture • Fatigue of WC-CoCr - the picture folks took back from Ottawa meeting

  28. Fatigue and fracture • Findings of cracking by AFRL (Bob Ware) • Careful analysis done at NRC (Jason Dyer, Peter Au) • WC-CoCr fails, cracks and delaminates under high compressive load (R=-1) • 0.003” coating, failure at 180 ksi and above • 0.010” coating, failure at 125 ksi and above (note that thicker coating carries more load) • cracks grow down from coating surface and often run parallel to interface (similar mechanism to that designed into composites) • cracks do not appear to propagate from coating into substrate • Surfaces of WC-CoCr fatigue specimens from Southwest Aeroservice also show crack pattern and some spalling at failure and runout • This shows there may be operational limits of WC-CoCr

  29. Where should we be testing? What are the real-world requirements? What are the functional limits of WC-CoCr and WC-Co? Questions:

  30. Fatigue and cracking - historical • Fracture data - John Quets, Shane Arthur • WC-Co initially designed using bend test cracking data • WC-CoCr designed to have better corrosion performance, but lower fracture strength • So, WC composite coatings balance hardness and wear resistance against brittleness (fracture strength) 1998 - Crack-like indications found by FPI on aft side of WC-CoCr-coated Lufthansa landing gear. Barkhausen analysis by Boeing showed no crack propagation into steel. Returned to service - no reported problems. Bend test of Praxair WC-CoCr. Reported by Jay Randolph, Delta Airlines, July 1998

  31. Landing gear design and fatigue testing • Designers do not design to specimen test data • Coupons provide stress engineers the data to start analyzing for customer and air-worthiness justification • Difficult to translate from load on full scale item to stress on test coupon • Qualification always depends on full-scale item fatigue testing under spectrum loading to 2 or 4 lifetimes • Bulk of public domain data for AerMet 100 was run at 150 ksi or less (Roger Eybel) • a few points were run higher for interest sake

  32. Fatigue - Loads on Landing Gear

  33. Fatigue - Loads on Landing Gear • Makes no sense to test coatings above levels used in full rig tests • Looks as though we have the following maximum needs: • Commercial 170 ksi, R=0.1 • Military, typical 180 ksi, R=-1 • Military, high performance 240 ksi, R=-1 • Questions: • At what loads/cycles were F-18 landing gear qualified? • Do you really go to yield thousands of times?

  34. Corrosion Additional tests planned samples made Fatigue C-HCAT testing 0.003” WC-CoCr below 180 ksi Rethinking tests for 0.010” WC-CoCr Comparative testing with SW Aero WC-CoCr and WC-Co Embrittlement Environmental embritt. Ball impact - in progress Producibility testing Heroux - grinding, stripping, NDI, fluids, etc. Rig testing BFG, Messier-Dowty Flight testing NADEP-JAX P3 DND CC-130 Summary of major ongoing work

  35. Remaining issues being resolved • US-HCAT corrosion testing to be redone • obviously testing problem • Fatigue testing • Not a structural issue that will cause failure, but a functional issue that will impose limits • Clearly define fatigue limits and requirements • Understand strain-to-failure, fatigue, residual stress relationships • Definition of load/thickness limits for WC-Co as done for WC-CoCr • WC-CoCr with hourglass specimens to define S/N curve comparable with WC-Co per JTP?

  36. Commercial no brainer - in production Military - general likely to work with WC-Co may be near edge of envelope for WC-CoCr High performance military (primarily fighters) need to define operational loads carefully to match qual of existing gear may need lower hardness, higher toughness material Full article tests - rig, flight Where does qualification look good?

  37. Remaining issues • US-HCAT corrosion testing to be redone • obviously testing problem • Fatigue testing of WC-CoCr with hourglass specimens • define S/N curve comparable with WC-Co per JTP • Definition of load/thickness limits for WC-Co • as done for WC-CoCr

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