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STRESS ANALYSIS OF THE EURATOM LCT CASE AND WINDING AS A CONTACT PROBLEM
A. Maurer
To cite this version:
A. Maurer. STRESS ANALYSIS OF THE EURATOM LCT CASE AND WINDING AS A CONTACT PROBLEM. Journal de Physique Colloques, 1984, 45 (C1), pp.C1-897-C1-900.
�10.1051/jphyscol:19841183�. �jpa-00223659�
JOURNAL DE PHYSIQUE
Colloque C1, supplement au no 1 , Tome 45, janvier 1984 page Cl-897
STRESS A N A L Y S I S OF THE EURATOM LCT CASE AND W I N D I N G AS A CONTACT PROBLEM
A. Maurer
Siemens AG, Research Laboratories, 0-8520 ErZangen, F.R.G.
R6sumk: Dans l e c a d r e du p r o j e t LCT (Large C o i l T a s k ) , l ' a n a l y s e d e s e f f o r t s d e l a b o b i n e s u p r a c o n d u c t r i c e 2 champ t o r o i d a l a h t 6 r k a l i s 6 e 2 l ' a i d e d e l a mCthode d e s 6lCments f i n i s ( M S C ~ N A S T R A N ) . L ' a n a l y s e p r g c g d e n t e a r e v e l & non s e u l e m e n t l e s do- maines f o r t e m e n t c h a r g e s mais a 6galement mis en Q v i d e n c e l a n 6 c e s s i t C d e p r o c 6 d e r 2 q u e l q u e s a m b l i o r a t i o n s n o t a b l e s d a n s l e mod$le e t l a procbdure.
Les p r i n c i p a u x r b s u l t a t s s o n t r h c a p i t u l 6 s s u r d e s t a b l e a u x e t r e p r b s e n t h s graphiquement.
A b s t r a c t : For t h e Large C o i l Task (LCT), t h e s t r e s s a n a l y s i s of t h e s u p e r c o n d u c t i n g t o r o i d a l f i e l d c o i l i s performed u s i n g t h e f i n i t e e l e m e n t computer program MSC/
NASTRAN. The p r e v i o u s a n a l y s i s n o t o n l y showed h i g h s t r e s s e d r e g i o n s , b u t a l s o made e v i d e n t t h a t t h e r e i s need f o r improvements i n modeling and p r o c e d u r e .
The most r e l e v a n t r e s u l t s a r e p r e s e n t e d i n t a b l e s o r g r a p h s .
1. I n t r o d u c t i o n I t i s a n t i c i ~ a t e d The customer (KfK)
t h a t t h e European LCT c o i l w i l l be completed i n e a r l y autumn 1983.
I and t h e m a n u f a c t u r e r (Siemens) i s s u e d a j o i n t r e p o r t on t h e ad- vanced s t a t e of m a n u f a c t u r e of winding and c a s i n g one y e a r ago / I / . A f t e r t h e planned a c c e p t a n c e t e s t s i n t h e K a r l s r u h e t e s t f a c i l i t y TOSKA / 2 / s c h e d u l e d f o r t h e end of 1 9 8 3 , a c t u a l t e s t o p e r a t i o n w i l l commence t o g e t h e r w i t h t h e c o i l s of t h e f i v e o t h e r m a n u f a c t u r e r s i n t h e Large C o i l T e s t F a c i l i t y (LCTF) i n Oak R i d g e , USA 131-
The m e c h a n i c a l s t r e s s a n a l y s i s of t h e European LCT c o i l i s completed. I t was p e r - formed on t h e f i n a l i z e d d e s i g n u s i n g t h e f i n i t e e l e m e n t method (FEM). I t c o m p r i s e s t h e g l o b a l s t r u c t u r a l a n a l y s i s and d e t a i l e d a n a l y s e s w i t h t h e aim o f o b t a i n i n g a n o v e r a l l p i c t u r e of t h e s t r e s s d i s t r i b u t i o n , a s w e l l a s i n f o r m a t i o n on d e f o r m a t i o n s and peak s t r e s s e s i n s u b s t r u c t u r e s .
Compared w i t h t h e p r e v i o u s s t r u c t u r a l a n a l y s i s / 4 / i m p o r t a n t i n n o v a t i o n s were nec- e s s a r y which made it p o s s i b l e t o b e t t e r d e s c r i b e t h e a c t u a l m e c h a n i c a l b e h a v i o u r of t h e c o i l . P a r t i c u l a r emphasis was l a i d on t h e s o l u t i o n of t h e c o n t a c t problem between winding and c a s i n g on t h e one hand and between c a s i n g and LCTF on t h e o t h e r . The s t a n d a r d s t a t i c a n a l y s i s i n t h e computer program MSC/NASTRAN was m o d i f i e d by t h e u s e r 1 5 1 .
2. G l o b a l s t r u c t u r a l a n a l y s i s 2.1 F i n i t e e l e m e n t model
The model of t h e e n t i r e s t r u c t u r e , e x c l u d i n g t h e s u p p l y t o w e r , i s shown i n F i g s . 1 and 2. The m a g n e t i c a l l y a c t i v e winding i s b u i l t up from 8-node s o l i d e l e m e n t s
(HEXA). F o r modeling of t h e c a s i n g , i n g e n e r a l , 4-node p l a t e e l e m e n t s w i t h mem- b r a n e , bending and s h e a r s t i f f n e s s e s were used. For t h e f o r g i n g w i t h i n t h e c o r n e r r e g i o n , 8-node s o l i d e l e m e n t s a r e more s u i t a b l e .
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19841183
Cl-898 JOURNAL DE PHYSIQUE
FE-model LC1 6401 mechanical structural snalys~r
Y
4 outer '("9 5 Front part (forging) 6 Side wall (back) 7 Inner suppan plate 8 Outer support plate
Fig. 1: Finite element model LCT6401 for structural analysis Fig,Z: Finite element model'of casing and fo4ging part of coil and casing, final design
2.2 M a t e r i a l p r o p e r t i e s
The complete s e t of m a t e r i a l d a t a c o m p r i s e s Young's m o d u l i , P o i s s o n r a t i o s , s h e a r moduli a t 4 K and mean t h e r m a l c o e f f i c i e n t s of e x p a n s i o n f o r t h e r a n g e between room
t e m p e r a t u r e (293 K ) and o p e r a t i n g t e m p e r a t u r e ( 4 K ) . The winding i s t r e g a r d e d a s a composite m a t e r i a l w i t h o r t h o t r o p i c m a t e r i a l b e h a v i o u r . The o v e r a l l m a t e r i a l prop- e r t i e s of t h e winding were n u m e r i c a l l y d e t e r m i n e d w i t h t h e a i d of a d e t a i l e d FE a n a l y s i s . For t h e g l a s s - f i b r e r e i n f o r c e d epoxy l a y e r s between winding and c a s i n g , t r a n s v e r s e - i s o t r o p i c m a t e r i a l b e h a v i o u r i s assumed.
2.3 F o r c e t r a n s m i s s i o n
T r e a t m e n t of t h e f o r c e t r a n s m i s s i o n r e s u l t s i n a 2-body c o n t a c t problem between winding and c a s i n g ( F i g . 3 ) . The s o l u t i o n of t h e c o n t a c t problem i s l i m i t e d t o t h e normal components.of d i s p l a c e m e n t and c o n t a c t f o r c e .
It i s assumed t h a t t h e c o n t a c t s u r f a c e s s l i d e a g a i n s t each o t h e r w i t h o u t f r i c t i o n . At t h e p o s s i b l e c o n t a c t p o i n t s , e i t h e r t h e c o n t a c t f o r c e o r t h e gap w i d t h normal t o t h e c o n t a c t s u r f a c e i s c a l c u l a t e d , t h i s depending on whether c o n t a c t i s c l o s e d o r open. The n o n - l i n e a r c o n t a c t problem i s s o l v e d n u m e r i c a l l y a s a s e q u e n c e of l i n e a r s t a t i c problems. The i t e r a t i v e p r o c e s s r e q u i r e d f o r t h i s p u r p o s e i s e x e c u t e d a u t o m a t i c a l l y d u r i n g t h e FE-program MSCINASTRAN.
-+---I
at outer ring - - -
Epoxy layer at Inner ilng
Epoxy
Palr of Load Care
Grid paint of FE-model
@ Grid po~nt of two palrr of contact potnta
Cornbmauon of
7 bar lnlemal pressure load thermal load due to cool down lo 4K magnetic load (Normal) + L C 2 magnetic load (Ail A) + LC 2 magnet. load (All. 0) +LC 2 rnagnetc load (AILC) +LC 2 LC 3 + 1 0 * pulse field base load (PF) LC4+1.1 * PF
L C 5 + 1 0 PF LC6 + 1.4 * PF
contact polnt~ Outer carlng contour LC
% deslgn operatlog current
rnllnn 1 7 Z d 5 fi
Fig. 3: Modeling of force transmission Table 1: Catalogue of load cases
2.4 Boundary c o n d i t i o n s
I n t e r f a c e s between c o i l and t e s t f a c i l i t y (LCTF) a r e t h e c o n t a c t s u r f a c e s a t t h e f r o n t of t h e f o r g i n g , i n t h e e x t e r n a l c o r n e r a r e a of t h e s i d e , w a l l s and a l o n g t h e b r a c k e t keyway i n t h e two h o r i z o n t a l s u p p o r t p l a t e s . I t i s assumed t h a t t h e m a t i n g p i e c e s of t h e LCTF - t h a t i s , t h e c e n t r a l bucking p o s t , t o r q u e r i n g s and b r a c k e t s -
a r e r i g i d . Only p r e s s u r e f o r c e s can be t r a n s m i t t e d a t any of t h e i n t e r f a c e s . Under t h e s e c o n d i t i o n s , t h e problem of t h e load-dependent boundary c o n d i t i o n s r e d u c e s t o a one-body c o n t a c t problem.
2.5 Load c a s e s
The f o l l o w i n g b a s i c l o a d c a s e s a r e t o be t a k e n i n t o a c c o u n t :
- h y d r o s t a t i c i n t e r n a l p r e s s u r e of 7 b a r between winding and c a s i n g
- t h e r m a l load due t o cool-down from room t e m p e r a t u r e t o 4 K
- magnetic l o a d s i n t h e t o r o i d a l and t h e p o l o i d a l f i e l d s . The load c a s e combinations a r e ' l i s t e d i n Table 1.
The l o a d s a r i s i n g d u r i n g winding were t a k e n i n t o a c c o u n t i n a s e p a r a t e s t r e s s a n a l y s i s 161.
2.6 R e s u l t s
Due t o l o a d symmetry, t h e s t r e s s a n a l y s i s can be l i m i t e d t o t h e upper h a l f of t h e s t r u c t u r e , e x c e p t f o r Load Case 9. I n t h e magnetic o u t - o f - p l a n e l o a d c a s e ( L C ~ , L C ~ ) t h e maximum d i s p l a c e m e n t of 4 mm o c c u r s i n t h e a x i a l d i r e c t i o n . The maximum expansion of t h e minor d i a m e t e r of t h e D c o n t o u r i s 3 nun ( s i n g l e c o i l l o a d c a s e , Fig. 4 , t h e r m a l c o n t r a c t i o n e l i m i n a t e d ) .
The maximum Hencky-von Mises e q u i v a l e n t s t r e s s e s a r e compiled i n Table 2 f o r s e - l e c t e d load c a s e s .
COII dome entrance
Back side wall (Sb)
outer ring I side wall edge N 1 side wall / bracket support /I 2
10
Table 2: Equivalent stresses q in the casing Fig. 4: Resulting deformations of side wall, coil, and cross sections
The d e s i g n l i m i t s p e r m i t e q u i v a l e n t s t r e s s e s up t o 700 N/mm2 i n t h e b a s e m a t e r i a l and 500 N/mm2 i n t h e welded m a t e r i a l . Out-of-plane (LC5, LC91 and s i n g l e c o i l load c a s e s (LC6, LC10) e x h i b i t h i g h e q u i v a l e n t s t r e s s e s up t o 508 N/mm2 i n t h e e x t e r n a l c o r n e r r e g i o n , b u t w i t h a s u f f i c i e n t s a f e t y margin. The maximum v a l u e s of t h e normal and s h e a r s t r e s s components i n t h e winding a r e compiled i n T a b l e 3 .
Caring stde wall Outel lace
Symbol Value
7 144
V-MIN -360 A-MAX-921
axla1
normal S~ASIBI shear rtrerrer
I value I load I Co114 I value, 1 load I cO'l
component Nimm care Pe"meter component N I ~care ~ p e y l e r
Fig.5: Equivalent stress contour lines in case and winding Table3: Maximum values of normal and shear stress in the coil winding
CI-900 J O U R N A L D E PHYSIQUE
Fig. 5 shows t h e c o n t o u r l i n e s of t h e e q u i v a l e n t s t r e s s i n c a s i n g and winding f o r t h e normal o p e r a t i n g c o n d i t i o n (LC3).
The s o l u t i o n of t h e c o n t a c t problem between winding and c a s i n g a s w e l l a s between magnet c a s i n g and t e s t f a c i l i t y (LCTF) r e s u l t s i n t h e p a r a m e t e r s : gap w i d t h , t a n g e n t i a l r e l a t i v e d i s p l a c e m e n t and c o n t a c t f o r c e o r b e a r i n g p r e s s u r e . The maxi- mum gap w i d t h a t v a r i o u s c o n t a c t a r e a s f o r t h e most i m p o r t a n t load c a s e s a r e com- p i l e d i n Table 4.
Contour lhnes Contour lhnes Contour llnes V-MIN. - 0 2 4 V = M I N =-049 V-MIN. - 0
~ = M A x - 1 3 3 A = M A X - 0.18 A=MAXm50.8 Gap width at Az8muthal Contact farces ,nner ring sliding movement at outer rlng
~n mm a! outer rlng ,n mm I" Nlmm'
Fig. 6: Results from contact problem:
Gap, sliding movement, contact force
Cornour llnes Symbol Value
1 0.01
2 0.02
3 0.03
4 0.04
5 0.05
Gap wldlh at stde wall
~n rnm
maximum value ol gap width in mm at
1
Wll Il9O0 Wll ,loo WISI LCTWFI
3 1 1.3 0.8 <0.1 0.1 I I -Inner ring
1.4 0.9 0.8
region
10 2.1 1.1 0.5 0.9
1.4 0.8 0.5 0.8
6 2.0 1.0 0.1 0.7
Table 4: Maximum gap widths at contact surfaces Sl - Side wall
(front)
For a l l l o a d c a s e s , t h e winding i s r a i s e d away from t h e e n t i r e i n n e r r i n g . Trans- m i s s i o n of f o r c e between winding and i n n e r r i n g i s g u a r a n t e e d around a l m o s t t h e e n t i r e p e r i m e t e r . Only i n one s m a l l r e g i o n i n f r o n t of t h e s u p p l y tower opening (70" p o s i t i o n ) does t h e winding d e t a c h from t h e o u t e r r i n g (max. 0.35 mm, LClO), a s i t i s p r e s s e d i n t o 'the tower opening. A t t h e b o u n d a r i e s of t h e gap i n t h e o u t e r r i n g , t h e b e a r i n g p r e s s u r e i n t h e nominal load c a s e (LC3) a t t a i n s 51 N/mrn2 ( F i g . 6 ) . 2.7 S i z e of problem
The s i z e of t h e problem i s c h a r a c t e r i z e d by t h e f o l l o w i n g d a t a (LC 1 - 8 , 1 0 /LC 9 ) :
Grid p o i n t s (2000/3800) Elements (1550/3100)
Degrees of freedom (6300/12700) C o n t a c t p o i n t s ( 6 0 0 / 7 0 0 ) .
A l l computations were performed on a CDC-Cyber 176 computer.
3. Conclusions
The FE s t r u c t u r a l a n a l y s i s was performed t a k i n g i n t o a c c o u n t t h e c o n t a c t problem between winding and c a s i n g , a s w e l l a s between c a s i n g and LCTF. The maximum s t r e s s e s i n t h e c a s i n g (be= 508 N / d ) and i n t h e winding (by = 1 2 1 N/mm2,
rrcp = 20 N/mm2) a r e h i g h , b u t n o t c r i t i c a l . However, i t i s known t h a t d e t a i l a n a l y s i s i n h i g h l y - s t r e s s e d c a s i n g c o r n e r s r e s u l t s i n much h i g h e r s t r e s s e s t h a n t h e g l o b a l s t r u c t u r a l a n a l y s i s . For t h i s r e a s o n , a r e f i n e d model of a c a s i n g c r o s s - s e c t i o n i n t h e m i d d l e f r o n t a r e a was p r e p a r e d and a n a l y s e d . The peak s t r e s s was 680 N/mm2. A f u r t h e r d e t a i l e d a n a l y s i s was performed f o r t h e s u p p l y tower.
References
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/ 2 / KRAUTH H., e t a l . ; Proc. 9 t h Symp. Eng. P r o b l . Fus. R e s e a r c h , Chicago (1981).
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/ 4 / MAURER A . , IEEE Trans. M a g n e t i c s , MAG-17, No. 5 , (1981) pp. 2093-2096.
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