• The FEM model foresees the AU-BU gap to reduce uniformly with time of ~5mm along the radial (X in the TGCS reference frame) direction, and a global misalignment between the two sub-components of 1.4mm along the vertical direction. No out of horizontal plane (Y axis) displacementsare predicted.

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

BU

_16

BU

_18

BU

_20

BU

_21

BU

_23

BU

_24

BU

_25

BU

_27

BU

_28

BU

_29

BU

_32

BU

_33

BU

_34

BU

_35

BU

_38

BU

_39

BU

_41

BU

_43

BU

_45

BU

_46

BU

_47

BU

_49

BU

_51

BU

_53

BU

_55

BU

_57

BU

_58

BU

_59

BU

_60

BU

_62

BU

_63

BU

_64

BU

_65

BU

_67

BU

_68

BU

_69

BU

_70

BU

_73

BU

_74

BU

_75

BU

_76

BU

_78

BU

_79

BU

_80

BU

_81

BU

_82

BU

_83

All fiducials Z-displacements [mm]

FEM Root pass

FEM 25mm

FEM 90mm

DI Root pass

DI 25mm

DI 90mm

Comparison of FEM Predicted and Measured values of the TF coil closure welding distortion

Edoardo Pompa, SETIS & University of Rome Tor Vergata; Marc Jimenez, Gabriele D'Amico, Boris Bellesia, Alessandro Bonito-Oliva, Fusion for Energy

26th International Conference on Magnet Technology , September 22 - 27 , 2019 - Level 2 Posters 2I.D. number: Mon-Af-Po1.17-03 [55]

• Toroidal Field Coils Cases (TFCC) areSS316LN structures, which have towithstand strong magnetic fields (around12 T) in order to confine the hightemperature plasma (150M C°)

• Welding distortions can compromise thefinal shape of the assembly, generatingout-of-tolerances in the interface areasthat cannot be recovered by the extra-material foreseen.

• A Finite Elements Model has beendeveloped by Enginsoft S.p.A incollaboration with SIMIC and F4E.

• In July 2019 the welding phase of TFC09has been completed, monitoring thecase deformation by fiducial points alongthe whole process.

1. Introduction 2. FEM model definition and survey setup• Theoretical and technical methods applied to the model:

• Quasi-steady state analytical solution (Rosenthal) to de-couple the thermo-mechanicalanalysis.

• ‘Birth’ and ‘death’ technique to simulate material deposition during weld.• Clustering technique of the weld passes to achieve mesh reduction maintaining as much

as possible the real sequence in the material deposition.• Tuning of the model through experimental campaign:

• First stage: welding of six qualification coupons. Measured displacements andtemperatures have been used as calibration parameters (cut-off temperatures and coolinglaw, chord mesh size and coefficient of thermal expansion (CTE) of chord material). A blindtest on a coupon has been carried out to final validate the model.

• Second stage: more refined tuning of the parameters on three TFCC full scale mockups,reproducing three zones of the case.

• Deformation of the TFCC structure has been monitored approximately every 25mm of deposited materialby laser tracking survey. The system accuracy depends on the distance from the target, the number offiducials and the number of position of the LT used. The uncertainty of the measurement evaluated isabout 0.2 mm. Quick surveys on 45 accessible fiducial points on the case with high repeatability.

Globally, the model reproduces the with good fidelity the TFCC deformation, in terms of behavior of deformations and order of magnitude of the displacements. Further work is foreseen in order to improve the prediction of deformation in specific areas (IOIS), while maintaining the global coherence. Increasingthe structure stiffness, fine-tuning of material properties are foreseen as possible solutions to improve the model prediction capabilities.

3. Results comparison• The TFCC full model (190k elements)

includes all the steps of the realwelding sequence, tack weld, buttweld, poloidal weld and splice platesweld.

• FEM boundary conditions allows all theDOF of the support with minimumreaction forces. The real supportconfiguration only allows BU case tomove, while AU remains fixed along theprocess. FEM deformations have beenfiltered with the average values of thedisplacements of the AU fiducialspoints in order to achieve the sameconfiguration of the DI.

4. Conclusions and future activities

3a. Butt weld phase

3b. Poloidal weld phaseAnalysis step Bevel fill [mm]

Tack Weld 1 -

Butt Weld Root Pass 8 6

25% 12 25

50% 15 50

75% 18 70

End 21 90

Poloidal Weld Root Pass 31 6

50% 73 55

End 54 110

Splice Plates Weld Root Pass 57 6

25% 58 25

50% 59 50

End 61 90

FE

M t

ech

niq

ue

s

Su

rvey s

etu

p

Ste

ps c

om

pari

so

n

Fid

ucia

l

po

int

-9.00

-8.00

-7.00

-6.00

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

1.00

TackWeld

Root pass 25mm 50mm 70mm 90mm

BU_70 X-displacements [mm]

FEM

DI

• The DI reported ~6mm of average closureafter the first 25mm of material deposition inthe chamfer, achieving at the end of the weldan average 7mm closure between parts.

• The cases misalignment along the verticaldirection has been verified by the DI data.The measurements show the same order ofmagnitude, but the real component present ahigher degree of misalignment localized inthe termination area.

• Only AP and BP plates have been foreseen to deform under the welding loads. The FEM model predicts negligible deformations on the rest of the case. • The FEM prediction is localized in the bevel zone, while the DI demonstrated to be extended to the case sides. This caused

the fiducials on the IOIS interfaces to rotate according to the cases sides angular deformation.• By taking into account only the fiducials not affected by the angular deformation, the average X displacements reported

from the DI are in line with the model.

FEM DI

IOIS

fid

ucia

ls

XY

-pla

ne

dis

pla

cem

en

ts

[mm

]

Z

XY

-9.00

-8.00

-7.00

-6.00

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

Root pass 55mm 110mm

Average X-displacements [mm]

FEM

DI

-8.00

-7.00

-6.00

-5.00

-4.00

-3.00

-2.00

-1.00

0.00Tack Weld Root pass 25mm 50mm 70mm 90mm

Average X-displacements [mm]

FEM

DI