Summary of first round of testing of shim concept for modular coil assembly

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.