Upload
philippa-terry
View
216
Download
0
Embed Size (px)
DESCRIPTION
NCSX March 16,20073 Testing Setup A traditional tension/compression testing machine has been configure to pull “double shear” combinations. Side rams allow the application of normal (transverse) loads
Citation preview
NCSX
Friction Coating Peer Review
March 16, 2007
NCSX
March 16,2007 2
NCSXIntroduction
• WBS 14 will use some revision of the 0.5” McGinnis/Williamson shim (see left) between modular coils
• Friction-encouraging and insulating properties are needed in these shims
March 16,2007 3
NCSXTesting Setup
• A traditional tension/compression testing machine has been configure to pull “double shear” combinations.
• Side rams allow the application of normal (transverse) loads
March 16,2007 4
NCSXTypical Test Combination
• A 0.38” thick x 1.00” wide center element receives the application of friction-encouraging medium (if any)
• Wider (1.50”) side plates are added to each side of the center element with an axial overlap of 1.0”
• The normal/transverse load (10 kip max) is added at the center of the overlap areas (2 in**2 total area)
March 16,2007 5
NCSX2nd Design Test Combination
• The original design called for a maximum loading of 10 kip over the available area
• A choice was made to reduce the test area rather than upgrade the test rig after analysts began predicting 17 ksi loading needs.
• The lessened area results in 10 kip max applied on two series ½ in**2 areas (1 in**2 total)
March 16,2007 6
NCSXEarly Test Observations
• File 070129Summary.xls lists the outcomes of 21 trials– G-10 on SS (ambient,1trial) m=0.18– SS on SS (amb/cold, 4 trials) m=0.21-0.26– SS/diamond/SS (amb/cold, 16 trials) mavg=0.53
• Many combinations
• The fundamental failure in the diamond-assisted trials was the tearing of the seated diamonds along/through the surface of the stainless– The tear-outs look like aerial views of perfectly plowed fields– This may be the functional limit of the material
March 16,2007 7
NCSXEmergent Bad News
• The nickel-bound CT-provided diamond coating could not survive LN2 dunk testing– The coating bubbled and flaked
off
• The epoxy in the epoxy-bound diamond coating seemed to becomes a lubricant after the joints’ first “give” at ultimate slip load
March 16,2007 8
NCSXBetter Product
• Ceradyne’s EKAgrip10 was deposited onto 4 mil shim stock and tested.– CoeffFricton Mu’s of 0.576 and 0.542 were obtained at
loadings of 6 ksi and 9.5 ksi respectively.– Survived the dunk test without incident– Diamond size is small (~0.4 mil); nice for ass’y crews
March 16,2007 9
NCSXReally Better Solution
• Plasma-sprayed alumina emerged as the big winner– 1) Mu's from 0.50 to 0.71 at pressures from 6 ksi to 17 ksi– 2) Infinite electrical isolation to 45 ksi compressive
loading (at 9 volts)– 3) The ability to "give" as the test set-up (always
imperfect) aligns itself while the slip load is applied to failure
– 4) The ability to maintain its peak mu (and load) during slip to failure. The diamond solutions fall in load capacity after slipping starts.
March 16,2007 10
NCSXAlumina - Linear Relationship?
Coefficient of Friction - Alumina
0.45
0.5
0.55
0.6
0.65
0.7
0.75
5000 7000 9000 11000 13000 15000 17000 19000
Transverse/Normal Loading (PSI)
App
aren
t Mu
Alumina
w/o binderw/o binder
Nice outlier
March 16,2007 11
NCSXAlumina Images
March 16,2007 12
NCSXNext Steps
• Finish scan of alumina with & without binder
• Perform cycle testing at ZZ% (90?) of 17 ksi slip load– Need chit (# cycles, % of slip)
• Investigate/Procure on-site plasma spray rig
• Others?