MID-ELM-BOLT-FOUNDATION--LOADS-REVA-2-24-11

PARAMETRIC FOUNDATION & BOLT STUDY February 24, 20111

ITER MID ELM

FOUNDATION & BOLT LOADS STUDY

Parametric Stress Analysis

February 24, 2011


Objectives

• Determine All Loads & Moments for the Mid Elm– Summarize all loads at local coordinate systems at each foundation pad

– Repeat the evaluation for each of the three load steps (See PDR Update 12-2-10)

• Provide Tabular summaries of the Foundation loads for all three load cases.– First Load Step is Thermal Loads

– Second Load Step is combined Thermal + Lorentz Load Toward Reactor Foundation Wall

– Third Load Step is combined Thermal + Lorentz Load Toward Plasma

• Provide a hand calculation of the Poloidal Foundation stress

• Provide Tabular summaries of the loads on the Poloidal & Corner Brackets– Apply these loads to Sub-Models of the brackets with bolt details defined.

– Evaluate the Current Foundation Rail Stresses with all three load cases

– Evaluate the Bolt loads on these brackets with all three load cases

• Complete a Design of Experiments Optimization of the Poloidal Bracket Rail– Parametrically adjust the length of the foundation rail width

– Illustrate sensitivity charts and response envelopes of the bolts and rail stresses as a

function of these changes

– Identify several candidate designs that will minimize the rail stresses

• Evaluate the Corner Bracket Rails based on the current design

• Provide conclusions and recommendations


PDR -ASSUMPTIONS

• The interface between the MGO insulation and the Coil is assumed to be

bonded contact.

– Conservative since transverse Lorentz loads could cycle the coil in tension.

– Additional work to characterize and calibrate the load transfer is in process.

• A reference temperature of 100 C is applied to all materials.

– This accounts for displacements of the reactor to boundary interface.

• Error is small since thermal expansion coefficients are similar

– Future work will map boundary thermal displacements with APDL script

• Additional reactor displacement to be added based on 100 C temperatures.

• Bonded thermal Contact is assumed between the brackets and coils

although mechanical constraint is limited to end points

• Surrounding Blanket and reactor structures are uniform 100 C

• All analysis is steady state3


Allowables and Acceptance Criteria

100C 200C 100C 200C

Primary Stress (PM, PL, PB)

General Primary Membrane 1.0 K Sm 120 108 147 130

Local primary membrane 1.5 K Sm 180 162 220.5 195

Primary Membrane plus bending 1.5 K Sm 180 162 220.5 195

Secondary (Q) (ie thermal) 3.0 K Sm 360 324 441 390

CuCrZr-IG 316L(N)-IG

Metalic Structure Acceptance Criteria (SDC-IC Appendix D)

Temperature 100C 200C 100C 200C

Minimum Ultimate Tensile Strength, Su 359 323 458 425

Minimum Yield Strength, Sy 253 235 172 144

Design Stress Intensity Limit, Sm 120 108 147 130

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Stress Limits (SDC -IC), MPa


Stress Endurance Limit, Se (=30% Su)

ITER_D_3VY7G5 V1.2

Max Shear Strength = 147/2 = 73.5Mpa = 10,660 Psi


FOUNDATION LOAD ANALYSIS

The PDR version (12-2-10) of the MID ELM is used to evaluate the foundation loads

POLOIDAL BRACKETCORNER BRACKET

Rigid Foundation at all supports

Loads Calculated at the Interface to the reactor vessel

Symmetric Constraint

Symmetric Constraint

5


ELM LORENTZ LOAD VS POSITION

Applied Maximum Lorentz Loads For Stress Range Calculation

(LFT)

(BOT)

(RHT)(TRC) (BLC)

Critical Quadrant

SECTOR 5 FE MODEL LOADS in GLOBAL COORDINATES

Fx Fy Fz

ELM_MD_BOT 121,508 60,907 -32,429

ELM_MD_BLC 105,447 77,208 -41,265

ELM_MD_LFT 236,652 185,166 7,491

OPPOSITE DIRECTION LOADING

ELM_MD_BOT -121,508 -60,907 +32,429

ELM_MD_BLC -105,447 -77,208 +41,265

ELM_MD_LFT -236,652 -185,166 -7491

(BRC)

6


TOROIDAL BRACKET

Reaction Coordinate Systems

The Toroidal Bolt Reaction Load Coordinate Systems are Defined

+z

+Y

+x

Coordinate System #180

Coordinate System #181


Corner Bracket


The Corner Bracket Bolt Reaction Load Coordinate Systems are Defined for the Bolt Pad and

on the Foundation

+z

+Y

+x

Lorentz Load

Mxx = 4,463 NM

Load step #3

Mxx = -850 NM

Load step #3

Coordinate System #182Coordinate System #183


Poloidal Bracket


+z

+Y

+x

The Poloidal Bolt Reaction Load Coordinate Systems are Defined at the Bolt Pad and on

the Foundation

Coordinate System #184Coordinate System #185


Foundation Pad Loads

** All loads are on foundation, reaction loads would have a reversed sign Highest Load Areas


POLOIDAL RAIL

Current Design

11


POLOIDAL FOUNDATION

COMPLEX – BENDING / SHEAR

12

Note: My : references Mz in loads

-7,053 psi = -48.6 Mpa

See Slide 18 for FE

Comparison 39 Mpa – 53 Mpa


POLOIDAL FOUNDATION

COMPLEX – BENDING / SHEAR

Note: Vy : references Vz in loads

Note: My : references Mz in loads





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Design Stress Limits

The hand calculations Show the Rail Stress is Acceptable

Directly at the foundation interface


Foundation/ Bolt Pad Analysis

14

POLOIDAL LOADS ON TOP OF COMB

CORNER LOADS ON TOP OF COMB


Poloidal Bolt / Foundation

Boundary Conditions

15

OUTSIDE INSIDE

BOLT1

BOLT3

BOLT4

* Preload is 182,000 N = 40,915 Lbf



Thermal Stress

16

The Average Poloidal Foundation Thermal Stresses are in excess of the Material Limits –

primarily around the top section of the rail.

21e6 Pa = 3,045 psiTemperature 100C 200C 100C 200C




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8.5e6 Pa = 1,232 psi

STRESS INTENSITY NORMAL STRESS

133e6 Pa = 19,290 psi 169e6 Pa = 24,511 psi



Thermal Stress + Lorentz Away From Plasma

17

The Average Poloidal Foundation Thermal +Lorentz Stresses are in excess of material

limits – primarily around the top section of the rail.

8e6 Pa = 1,160 psi Temperature 100C 200C 100C 200C




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56e6 Pa = 8,122 psi


189e6 Pa = 27,412 psi 260e6 Pa = 37,709 psi



Thermal Stress + Lorentz Toward Plasma

18

The Average Poloidal Foundation Thermal +Lorentz Stresses are in excess of the stress

limits – primarily on the top section of the rails.

87e6 Pa = 12,618 psi





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92e6 Pa = 13,343 psi


189e6 Pa = 27,412 psi 272e6 Pa = 39,450 psi


Normal Bolt Stress

19

Thermal + Lorentz

Toward Plasma

Thermal + Lorentz

Away From Plasma

210,000 N = 47,209 Lbf

172,000 N = 38,667 Lbf

The Load on Bolts 2 and 3 has excessive variation (8,542 Lbf) and will require a higher

preload or more bolts –The clamping force is not sufficient

Preload = 182,000 N = 40,915 Lbf


Poloidal Foundation

Parametric Study

20

OBJECTIVES:

1.) Use Load Step #3 (Lorentz Loads Toward Plasma) + Bolt Preloading

2.) Adjust the foundation width parameters and determine the impact on:

a.) The bolt working loads

b.) The foundation interface stress

c.) The rail & Attachment Stresses

3.) Make a recommendation based on these trends to assure an adequate design


Geometric Parameters

21

Smallest Option Evaluated Intermediate Option Evaluated

Largest Option EvaluatedInside Rail Dimension

0.0 to 15.5 mm

Outside Rail Dimension

55.0 to 65 mm


Sensitivity Charts for Bolt Loading

22

Similar Sensitivity on Bolt 4 and Bolt 3 for both rails

Bolt 1 and Bolt 2 are most influenced by the Inside Rail Length

Inside Rail

Outside Rail

Bolt 1Bolt 2

Bolt 3Bolt 4

Local Sensitivity Chart is based on Outside Rail 60 mm & Inside Rail = 8 mm; Preload = 2.184e5 N


Foundation Stress Sensitivity for Rail Parameter

Changes

23

Out Equiv Stress Inside Equiv StressOutside Stress

IntensityInside Stress

Intensity

Inside Rail

Outside Rail

The Inside Rail Dimension has the Largest Impact on the Foundation Stresses

Reduce foundation stress by changing inside rail dimensions

Local Sensitivity Chart is based on Outside Rail 60 mm & Inside Rail = 8 mm; Preload = 2.184e5 N


Stress Minimum Value

24

The Rail Dimensions Required to Minimize the Foundation Stress

Outside Rail of 60 mm and inside Rail 10 mm

** Table assumes a bolt preload of 218,400 N (49,098 Lbf) and applied Lorentz load toward plasma


Bolt Load Minimum Value

25

The Rail Dimensions Required to Minimize the Max Working Load of Bolt

Outside Rail of 60 mm and inside Rail 10 mm

** Table assumes a bolt preload of 218,400 N (49,098 Lbf) and applied Lorentz load toward plasma


Bolt #1 Working Load - Response Envelope

Function of Rail Width Changes

26

Inside > 8mm

Outside = anything

Load =2.184 e5 N = 49,098 Lbf

Bolt Pre-Load 2.184 e5 N

Setting Outside Rail to anything if the inside railis greater than 8 mm

Results in all working bolt loads of about 49,098 Lbf (very low fatigue Load range)

Preload = 2.184e5 N = 49,098 Lbf




27

Inside > 10 mm

Outside > 58 mm

Load =2.189 e5 N = 49,210 Lbf


Setting Inside Rail Greater than 10 mm and the Outside Rail 58 mm or greater

Results in all working bolt loads of about 49,210 Lbf (fatigue Load range of 112 Lbf)

Preload = 2.184e5 N = 49,098 Lbf




28

If Inside = 8 mm then

Outside = 60

Load =2.196 e5 N = 49,368 Lbf

Setting Inside Rail Greater than 8 mm and the Outside Rail 60 mm or greater

Results in all working bolt loads of about 49,368 Lbf ( 270 lbf fatigue Load range)


Preload = 2.184e5 N = 49,098 Lbf




29

Inside = 8 mm

Outside = 60

Load =2.189 e5 N = 49,210 Lbf

Setting Inside Rail is 8 mm and the Outside Rail 60 mm or greater

Results in all working bolt loads of about 49,210 Lbf ( 112 lbs working fatigue load)

Preload = 2.184e5 N = 49,098 Lbf


Inside Foundation Face - Stress Intensity

30

Setting Inside Rail to 8 mm and the Outside Rail 60 mm

Results in a local minimum on the stress intensity of 101 Mpa which meets the criteria

If Inside = 8 mm then

Outside = 60 mm

Stress Intensity = 101 Mpa





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Outside Foundation Face - Stress Intensity

31

Setting Inside Rail Greater to 8 mm and the Outside Rail 60 mm

Results in a local minimum on the stress intensity 77 Mpa which meets the criteria

If Inside = 8 mm

Outside = 60 mm

Stress Intensity = 77 Mpa





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Stress Endurance Limit, Se (=30% Su)Current Design Approximated by this region 132 Mpa


Optimization Candidates

to Minimize Foundation Rail Stress

32

Rail Dimensions Outside

Foundation StressInside Foundation

Stress

Outside Stress

Intensity

Inside Stress

Intensity

Rail Dimensions Bolt Working Loads

(N)

Three Design Candidates Have Been Identified with the Optimizer


Optimized Poloidal / Foundation

Increased Preload = 2.184e5 N = 49,048 Lbf

Outside Rail = 60 mm Inside Rail = 10 mm

33



Thermal Stress + Lorentz Away from Plasma(Increased Pre-load)

34

The Average Poloidal Foundation Thermal +Lorentz Stresses are in excess of the stress

limits – primarily on the top section of the rails with Increased preloads

Addition of additional bolt should solve this concentration

290e6 Pa = 42,060 psi





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22e6 Pa = 3,190 psi


153e6 Pa = 22,190 psi

160e6 Pa = 23,206 psi



Thermal Stress + Lorentz Toward Plasma(Increased Pre-load)

35

The Average Poloidal Foundation Thermal +Lorentz Stresses are in excess of material limits –

primarily around the top section of the rail with increasing preload

Addition of an extra bolt should eliminate the bending issues

211e6 Pa = 30,603 psi





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88e6 Pa = 12,763 psi




Thermal Stress + Lorentz Toward Plasma(Increased Pre-load)

36

The Preload (49,098 lbf or100,828 psi ) is not sufficient to maintain clamp load

Additional bolt will be required for Poloidal Rail

Total DisplacementContact Stress

No Contact


Bolt Load vs. Load Step

37

Thermal + Lorentz

Away From Plasma

234,220 N = 52,654 Lbf

The Load on Bolts 3 and 4 has much lower load variation (3,556 lbf)

From increasing preload as expected

Preload = 218,400 N = 49,098Lbf

Thermal + Lorentz

Toward Plasma

Bolt Load Result is based on Outside Rail 60 mm & Inside Rail = 8 mm; Preload = 2.184e5 N


Corner Bolt / Foundation

38


Rigid Foundation


Boundary Conditions


Hex Dominant Mesh is complete on the corner Bracket


Mesh



Thermal Stress

41

The Average Poloidal Foundation Thermal Stresses are in excess of the material Limits

On the top section of the Rail - See next Slide

106e6 Pa = 15,374 psi Temperature 100C 200C 100C 200C




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Thermal Stress

42

The Average Poloidal Foundation Thermal Stresses exceed the material limits

for Stress Intensity and Fatigue Limits

164e6 Pa = 23,786 psi





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-144e6 Pa = 20,885psi




Thermal Stress + Lorentz Away From Plasma





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The Corner Foundation has Stress Intensity that is not within the Material Limits

A thicker width rail or gusset will be required

-95e6 Pa = -13,778 psi196e6 Pa = -28,427 psi

STRESS INTENSITYNORMAL STRESS



Thermal Stress + Lorentz Toward Plasma





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100e6 Pa = 14,503 psi

The Corner Foundation has Stresses that are not within the Material Limits

A thicker width rail or gusset will be required

84e6 Pa = 12,183 psi

STRESS INTENSITYNORMAL STRESS


Corner Bracket Bolt Load Vs Load Step

45

Thermal + Lorentz

Toward Plasma

Thermal + Lorentz

Away From Plasma

195,000 N = 43,837 Lbf

The Corner Foundation Bolt3 has significant load variation each cycle

Higher Stiffness Pad Similar to Others is Recommended

Preload 182,000 N = 40,915 Lbf


Corner Bracket Max Bolt Stress Vs Load Step

The Corner Foundation Bolt3 has significant Stress variation each cycle

Higher Stiffness Pad and Preload is Recommended


Contact Status

Demonstrates Insufficient Preloading

47

Thermal + Lorentz Away From Plasma Thermal + Lorentz Toward Plasma

The Corner Foundation Contact Status Has Separation at the Contact Interface

Preload of 182,000 N ( 40,915 Lbf) is not sufficient

Clamp Load Separation


Recommended Bolting Materials

48

The recommended preload is 2.184e5 N (49,048 Lbs)

For a bolt with minimum stress area of 0.4869 in^2 this is a 100,828 preload stress 718-Inconel is adequate and provides some margin for localized bolt bending due to eccentricities


Conclusions

• The reactions loads and moments are provided based on the PDR update applied loads and

assumptions.

• The loads on both Corner Bracket and Poloidal Bracket sub-models were provided.

• Hand Calculations with Complex Bending on the Poloidal Rail (48.6 Mpa) do not predict stress

issues on the foundation interface. This result supports the FE findings (53 Mpa).

• A Poloidal and Corner Bracket with Bolt Model was completed and stresses were shown to be

within limits at the foundation interface, however, the upper section on the rails have excessive

stresses.

• A design optimization was completed and several cases were identified that would minimize the

stresses on the Poloidal rail.

• The rail stresses with these optimized dimensions were completed to show that the Poloidal rail

will still need an additional bolt to minimize the bending.

• The magnitude of the bolt preload to assure fatigue loads are small was determined to be

49,048 Lbf.


Conclusions - Continued

• The sensitivity charts on the Poloidal Rail show that the Inner rail is the most critical dimension

to influence stress intensity and working bolt load. – The inner radius should not align with the bracket as was used in the PDR since stress intensity and bolt working loads

are increased .

• The Corner bracket rail width is also to small to support the current loads.

The initial preload (40,915 lbf) was not sufficient to maintain contact for Lorentz Load toward

the Plasma.

• The rail on the corner bracket should be optimized, however, it would be conservative to apply

the Poloidal Foundation results to this design as well.

• The isolated single bolt on the outside pad does not have adequate stiffness in comparison to

the other bolts on this bracket. This will likely be a fatigue problem is this is not extended to

provide a similar stiffness with two bolts.


Recommendations

• The foundation attachment design does not have sufficient (E/D) edge to diameter ratio. This should be

2.0 and at a minimum of 1.5 to have sufficient reliability.

• The Poloidal Foundation Rails should be increased to a width of 60 mm and positioned based on an Inner

Rail of 10 mm and the Outer Rail of 60 mm. This provide a Edge / Diameter (29.726/20=1.486).

• The bolting material should be Inconel 718 AMS-5662 with minimum strengths as specified in Military

Handbook could be used if shear strength is not critical.

• Add an addition bolt on the Poloidal Bracket to minimize bending and provide improved bolt fatigue life.

• Increase the Corner support stiffness and preload to control variation in Bolt Stress.

• These results are based on uniform temperatures and reference temperatures of 100 C. Any temperature

variations at the foundation would warrant additional study to include a thermal gradient through this sub-

model and possibly the reactor wall.

– The actual foundation temperature could be determined by applying the heat flux on the foundation

from the PDR model to a separate model of the reactor wall. Assume 100 C on one side of the

reactor wall model and apply a heat flux to the opposite end of the reactor wall to determine

accurate foundation temperatures for the sub-model analysis provided in this study.

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Documents

MID-ELM-BOLT-FOUNDATION--LOADS-REVA-2-24-11