HALLD TAGGER MAGNET STRUCTURAL ANALYSIS

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HALLD TAGGER MAGNETSTRUCTURAL ANALYSIS

Presented by William Crahen 6/10/09

•Pole Plate analysis

•Vacuum chamber analysis

•Vacuum chamber tie rods and brackets

1

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POLE PLATE ANALYSIS


•Minimize fastener count (machining) and confirm that they meet the load sequence requirements.

•Confirm that plate deformation (and gaps!) are minimal.

•Check that tapped holes in 1006 will not strip, or distort to the point they create a problem. 2

gap

Non-parallel Poles

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FASTENERS


2” 4140 HT ROD THREADED BOTH ENDS 2-4.5.

1 ¼” Grade 8 bolt to help compress O-ring.

24”

12”

1 ¼” Grade 8 bolt to prevent pole bending

½”-13 threaded rod Grade 8 equiv. to compress O-ring and prevent bowing of the vacuum chamber.

¾” rod threaded both ends- 11L17 or high strength allthread

3

Top plate

Bottom plateLower pole plate

Upper pole plate

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PULLING THE UPPER POLE DOWNCOMPRESSING THE O-RING


Pivot point

Ignore contribution of 28 threaded rods

11 bolts to compress O-ring

34”

15”

79300# @ 35% squeeze

"3479300"1511 boltF

lbfFbolt 16340

Preload these bolts to twice this= 32680 lbf, which is 32% of proof load for 1 ¼” bolt of grade 8 specification.

4

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2” MAIN TIE ROD FORCES


Pivot point

Ignore contribution of 11 bolts and O-ring force.

Inner and outer tie rods carry 5500 lbf. There are 8 upper brackets.

15.1”

12.9”

31.6”47.3” 25”

21 rods 2” dia.

Vacuum load from edge of chamber (does not include O-ring force)=2388 lbf * 7 locations=16716 lbf <<2388 value from Ansys.

Mag and vac force on pole face=312861 lbf

lbfFrod 32735For equilibrium:

lbfFrod 131250For specification (.5*proof):

3.1”

Weight of upper plates= 82054

5

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FEA using specified forces: Loads


131250

32688

gravity

Magnetic and vacuum force:312861

131250

5500

32688

32688

5500

2388

24”

Note: 24” is ~1/10th total plate length

These forces actually repeat every 31”,not 24”- therefore this adds a safety factor.

note: this is not the total load seen by the four ½”-13 tie rods. They also carry an O-ring compression force=4812, and a preload of 2000, for a total of 9200 lbf carried by the four tie rods.

6

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FEA using specified forces: Deformations


Manufacturing tolerance equal to +/-.005” exceeds this!

7

Note: The Glasgow University analysis predicted about twice this deformation- I have more confidence in my analysis.

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Noise level- machining tolerance issues 100 times greater.

8

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Ansys reported zero gap. This is penetration . Once again, surface motion is insignificant with respect to flatness.

9

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Stress in tapped holes in the 1006 Plates: Length of engagement=2*D.


Plate made of bubble gum- thread inserts all around?

10

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We plan to use thread inserts , but what length of engagement would carry the load without them?

Presented by William Crahen 6/10/09 11

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Reality check on equations for As and An:A simplified look at shear area.


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Calculation of tensile and shear areas


I will use the reality check value, as it is the smallest.

13

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Thread load capacity of 1006 Plates and vacuum chamber attachments:


Preload=32,688, but frictional forces from tightening are also significant. Insert needed.

Both of these fasteners can be threaded into the vacuum chamber under no load, then held stationary while hardened nuts at the other end apply the load. As the working load is much lower (5500# for ¾, and 2300# for the ½), and friction is not an issue, no inserts are needed.

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Bolts securing vacuum chamber bracket to the plates are preloaded to 6500#. Inserts not needed, but will be used in any case.

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VACUUM CHAMBER ANALYSIS


•Minimize the motion of the O-ring in contact with the poles

•Minimize the change in the opening width of the thin window flange to ~2mm

•Look at the overall plate motion and confirm that it isn’t much more than 2mm.

•Confirm that the stresses are acceptable

•Look at the effect of adding additional tie rods

15

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VACUUM CHAMBER ANALYSIS


•Minimize the motion of the O-ring in contact with the poles

•Minimize the change in the opening width of the thin window flange to ~2mm

•Look at the overall plate motion and confirm that it isn’t much more than 2mm.

•Confirm that the stresses are acceptable

•Look at the effect of adding additional tie rods

16

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Original configuration of the pole flange


The O-ring was modeled as six linear springs to get a fair approximation of it’s loads, and added to the vacuum load.

The midspan deflection was ~0.029”, even though outer tie rods were present. this seemed like an unacceptably large movement of a critical seal.

3/8” O-ring

Outer tie rods

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The solution was to add the ½”-13 tie rods to the edge of the flange:


O-ring motion reduced to ~.008”. We can now consider reducing the size of the O-ring from 3/8” to ¼”.

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The thin window flange had to much movement- the ‘C’ ribs were not stiff enough

to limit the change in the opening width to 2mm.


Motion of single flange! The lower flange also moves upward.

19

The original design:

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BRUTE FORCE SOLUTION- DOUBLE THE AREA MOMENT OF INERTIA FOR THE RIBS.


newh

3

2

old

new

old

new

h

h

I

I

newold hh 3 2

Diameter=18.5”

20

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RESULTANT SKELETON DEFLECTION:


CHANGE IN OPENING WIDTH=.018+.051=.069”=1.75mm

Difference in values caused by gravity. Its effect is the difference from the average=.016”

21

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RESULTANT PLATE MOTION:


Plates close together= .034+.062=.096”=2.4mm

22

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VON-MISES STRESSES:


Ansys ‘hiccup’-presumably a small mesh problem.

23

Plate stresses well below the 16,700 psi limit as per ASME Boiler and Pressure vessel code

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VON-MISES STRESSES:


Bogus stress here- edge attachment of tie rod

Corner stress concentrator will yield locally.

The structural skeleton is also comfortably below the 16,700 psi pressure vessel limit for 316L.

24

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REALITY CHECK ON ANSYS DEFLECTION:


0.085”

20% DIFFERENCE.

25

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ADD A DIAGONAL TIE ROD?


TIE ROD HERE? PROBABLY NOT.

DEFLECTION=.027+.059=.086=2.2mm. Diagonal only buys us .43mm.

26

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BRACKET/TIE ROD ANALYSIS


•Look at the total bracket /tie rod deformation and stress.

•If the tie rod deformation is a significant portion, beef it up to reduce this.

•Modify the bracket as needed to reduce it’s total motion to ~0.5mm.

27

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ORIGIONAL BRACKET (8” x 4” x 3/8”wall):


Rigid body tube motion (plate motion)

Tube bending

.0036” rod stretch- not worth improving.

28

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New bracket (10” x 4” x ½” with center bolt):


Big improvement from .030”

Bolt added inside tube holds plate flatter.

29

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Loads applied to bracket:


5500#

8X 6500#

13799 x 1.077=14861#, and our preload is only 6500#. We still plan to use thread inserts here.

30

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Bracket stress:


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Summary:


•The pole deflection is on the order of achievable machining tolerance, and gaps induced by bending are essentially zero.

•The fasteners and tapped holes have been appropriately sized to prevent tensile failure and thread stripping.

•The Vacuum chamber design meets the deflection criteria, stress levels are lower than allowed by ASME Pressure vessel code, and the critical O-ring seal will experience acceptable variation in “squeeze” (~.008”).

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Remaining tasks:


•Investigate reducing the size of the O-rings from 3/8” to ¼”

•Analyze the coil attachments

•Analyze the thin window

•Analyze the Weldment that supports the main plates

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Additonal slides:


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CENTER OF GRAVITY OF CHAMBER:


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HALLD TAGGER MAGNET STRUCTURAL ANALYSIS