summary of first round of testing of shim concept for modular coil assembly
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Summary of first round of testing of shim concept for modular coil assembly. 8-28-06. Problem. Shear loading in the inboard regions has no manner in which to be resolved. From Art and H.M. modeling. - PowerPoint PPT PresentationTRANSCRIPT
Summary of first round of testing of shim concept for modular coil assembly
8-28-06
Problem
Shear loading in the inboard regions has no manner in which to
be resolved
From Art and H.M. modeling
Coefficent of Friction Needed to Prevent SlipNonLinear, Baseline w/Gaps at Wings - No Slip Inner Leg (hm10)
No Bolts in Inner Leg
0.000
0.150
0.300
0.450
0.600
0.750
0.900
cc2
b
cc2
int
bc2
brl
bc2
trl
bc2
tl
bc2
inb
ab
2b
l
ab
2tr
l
ab
2tl
ab
2in
b
aa
bl
aa
tr
aa
int
ab
brl
ab
tr
ab
int
bcb
rl
bct
rl
bct
l
bci
nb
ccb
ccin
t
Joint-Location
mu
Bottom Line: friction alone will not prevent sliding. (how much sliding that would ultimately result is unanswered)
Linear20°
H.M
E = 8.5 MpsiFreudenberg
Further Checking
The stress plots between the two models agree well with each other.
However, It appears that turning one coil non-linear at a time produces different compressive forces at coil joints (unbalanced) then cases where all coils exhibit like properties.
radial shear normal force vertical shear Total Shear Net Preload/boltBy Region within
JointAnaylis Type Fx, N Fy, N Fz, N Fxz at 80K, lbs
HM 39 all coils sliding abinb 2.85E+05 8.42E+05 6.56E+05 7.16E+05 45797 abinb 0.850Freudenberg 39*
(Nonlinear B)B sliding only abinb -5.34E+05 4.19E+04 -6.81E+05 8.65E+05 45798 abinb 20.663
Freudenberg 39* (Nonlinear A)
A sliding Only abinb -4.48E+05 -2.58E+05 -8.46E+05 9.57E+05 45798 abinb 3.709
Freudenberg 39* Linear (E = 8.5
Mpsi)Linear abinb -2.94E+05 -6.26E+05 -5.21E+05 5.98E+05 45799 abinb 0.955
Freudenberg 39* Linear (E = .085Mpsi)
Linear (reduced coil modulus)
abinb -4.07E+05 -5.76E+05 -5.70E+05 7.00E+05 45800 abinb 1.217
Required Friction
Coef
Concept to resolve shear forces
Add shear pins to prevent this motion from occurring
Calculation for size and number based on largest shear force from shim abinb
What an individual shim would look like
53 pins on approx 2.5” centers 70 pins on approx 2” centers
Design will be similar to the left figure (with 50 pins per section)
Pins and shims (up-close)
Large clearance holes are needed to allow for alignment
SST Shims, G-10 Shims, bushings and pins
Test Fixture
A prototype fixture containing 4 pins was designed and loaded
Stycast not shown
Pins are 2” apart
.625
Fixture
Fixture
Welded stud
bushing
epoxy
G-10 shim
Steel shim
Outer pull plate is Outer pull plate is invisibleinvisible
Stud Welding
• The four half inch studs were welded on at the MDL laboratory onto the two pull plates. The pins had very little tilt to them and were fairly normal to the plates.
• The weld bead was then ground off and the studs were cut back to 3/8” long.
• This procedure can be performed at PPPL in the same manner as was done at MDL.
• All other parts of the fixture (excluding the studs), were machined at a local machine shop.
Sample Preparation (Awaiting Insertion of the Stycast)
Imagine from cell phone (poor quality)
1/32” Groove for Stycast run off (two places)
Sample Preparation (Insertion of the Stycast)
Mixed Stycast 2850 with catalyst 23LV
Extracted using Walgreens syringe
Stycast was inserted from the top filling all four holes in this orientation
Stycast
Support Weight
First two holes (with pins up) were filled with 3cc’s of Stycast to the top
3cc’s were then placed in the other two holes and the top plate was placed down.
More Preparation pictures pool
Final Step (assembling top pull plate onto fixture)
Another View of Stycast Pool
Shim Test Fixture loaded into pull fixture
• Independent measuring extensometer installed on outer lower block via magnetic mount
• Max Load tested so far = 15,000 lbs (3750 lbs/pin)
• Stroke and load are measured by the 5-0 kip load cell on top of the machine (just outside the picture)
The “one armed bandit”
Hard to see, but the probe touches the bottom of the shim piece here.
Close up of the bandit
Prototype testing
Max loading of 15,000 lbs
First test
2 mil offset
Test Setup #2: left and right side measuring
All tests showed approximately 6-7 mils of deflection at 15,000 lbs
Finite Element Analysis
Experimental demonstrated .006-.007 in deflection for 15,000 lbs (3750 lbs/pin)
FEA Loading and setup
200 lb preload applied to bolts
15,000 lb tension load (top hole)
Model is fixed at bottom hole
Mesh
Frictionless contact between g-10 shims and outer pulling plates
Elastic Modulus
SST = 28 Mpsi
G-10 = 7 MpsiStycast 2850 = 1.05 Mpsi from Fermilab paper (TM-2339-E)
Deformation
Deflection (x 1e-2 in )
Stycast has frictionless contact with bushing, thus only compressive loading is seen by the Stycast.
Upward movement of 1.75 mils.
Stress Intensity on pins
Very Localized peak stress near the root of the pin, σnom approx 14 ksi
Post testing Observations
The analysis underestimated the experimentally observed deflection by a factor of 3.5. Why did this happen?
Post test Pictures
Top Pull Plate removed
Pictures of Stycast and bushings
Top View:
Bushing are not concentric
No cracking is seen.
ISO view:
Large gaps 1/8” are seen in the level of the stycast compared to the sst shim,
Pictures of Stycast and bushings
More gap pictures and a view of the relief groove milled into the shim.
Air Bubbles
After removing bottom pull plate and breaking the stycast, Multiple air bubbles were observed throughout the material (largest bubble approx dia = 3/16”)
Bubble
Bubble
Bubbles
Updated Analysis [Model changes to reflect post test observations]
• Gaps Introduced around pins on one side (see pictures above).
• Modulus reduced by 50% (estimate) to account for bubbles.
• Resulting Deflection is 7.35 mils
gaps
No gaps on reverse side
Solutions and Path Forward.
• Inject Stycast from the side of each hole (instead of top) using Zerc fittings and hypodermic needle.
• Two holes will be drilled to allow for insertion and vacuum pulling of stycast around each bushing.
• Deair stycast until bubbling has ceased using vacuum (Use prototype to test Stycast mixture for presence of bubbles)
• Limit stirring of Stycast• Test Stycast samples in LN2 environment to test
compressive strength.
Appendix: Bubble Solution
To ensure a void-free embedment, vacuum deairing should be used to remove any entrapped air introduced during the mixing operation. Vacuum deair mixture at 1-5 mm mercury. The foam will rise several times the liquid height and then subside. Continue vacuum deairing until most of the bubbling has ceased. This usually requires 3-10 minutes. To facilitate deairing in difficult to deair materials, add 1-3 drops of an air release agent, such as ANTIFOAM 88, into 100 grams of mixture. Gentle warming will also help, but working life will be shortened.