DESY Experiences in Hydroforming of Elliptical RF Cavities W. Singer • Introduction • Hydroforming technique (necking, expansion) • Nb tubes for hydroforming • Examples of RF performance W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Introduction Advantages of seamless cavity fabrication • no RRR degradation in the welding seam, in the heat affected zone HAZ and in the weld overlapping • no risk of equator weld contamination due to not sufficiently clean preparation for welding • no problem with pits in the HAZ, that are intensively in discussion last time • lower cost of fabrication can be expected, especially for large series. • less scattering in performance statistic of seamless cavity compare to welded cavities is to expect . W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Hydroforming technique Hydroforming consists of two steps: a) reduction of diameters at ends of tubes and iris areas (necking) b) tube expansion at the equator W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Step 1: necking Several necking methods were check out before the current necking procedure was established • spinning • necking by profile ring • hydraulic necking • electromagnetic strike necking, • verjungen (diameter reduction by push the tube end through the set of rings of smaller diameter) • rotary swaging (rundkneten) Principle of rotary swaging W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Step 1: necking • necking by spinning Not uniform necking at the iris area of tube end done at company HTI by spinning ( hole appeared during centrifugal barrel polishing). KEK necking machine (successful on Cu-tubes) In principle it works W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Step 1: necking (by profile ring) Improvement of the necking procedure and development of DESY necking equipment provided the success (combination of radial and axial movement ) Principle of diameter reduction in the tube end and iris area Principle of DESY necking equipment W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Step 1: necking (by profile ring) Seamless technique by hydroforming: step 1- necking DESY developed necking equipment (by profile ring) DESY Necking machine: new PC controlled necking procedure Reduction mechanism. Tubes after reduction in the iris areas W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Conclusion to necking: • spinning: works (essential wall thickness reduction close to iris, probably this can be improved by parameter optimization) • necking by profile ring: works (best results) • hydraulic necking: does not work (not round shape) • electromagnetic strike necking: works for Cu, can work on Nb only for bimetallic NbCu tubes (resistance of Nb is to high ), the shape is not sufficiently under control due to single strike • verjungen: works only for single cells (time consuming due to many rings, not optimal shape of the necking) • rotary swaging (rundkneten): works (damaging of the surface, significant work hardening) W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Step 2: Expansion (Hydroforming) First question. Hydroforming conditions ,parameters? Is the room temperature appropriate for hydroforming? Yes DESY data Dependence of the elongation on temperature. It make sense to perform hydroforming of niobium at room temperatures W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
How fast to perform the deformation (hydroforming)? Dependence of ∂ ε • maximum elongation of ε = − Strain rate 1 , sec ∂ niobium versus strain t rate (H, M, S different literature data). Correct strain rate should be chosen for hydroforming Chosen strain rate is between 0.01 sec-1 and 0.001 sec-1 Compilations of C. Antoine W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
250 Sigma, N/mm2 200 Pulsing of the 150 pressure 100 during 50 hydroforming 0 helps 0,00 0,20 0,40 0,60 0,80 Epsilon Heraeus Tube7. Paralel to axis, contin. Heraeus Tube7. Circum ferential, contin. Heraeus Tube7. Paralel to axis, stepw ise Heraeus Tube7. Circum ferential, stepw ise Comparison of the tensile test in continues and pulse regime The strain before necking can be increased by using a periodic stress fluctuation (pulse regime). Probably the pull-release regime of the deformation artificially increases the work-hardening of Nb in low-yield strength regions and therefore shift the break to higher elongations. W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Principle of hydroforming DESY hydroforming machine Tube Movable Matrix Fixed Matrix • Designed and build in Ptube sensor Russia (INR, Troitsk) Water Hydr. • Equipped with system Oil Hydr hydraulic systems and Pcyl system Lsensor Rsensor sensor software at DESY • From dimension is in position to produce only units of 3 cells DESY hydroforming machine W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Path D :\ 1 c e ll h yd ro fo rm in g \ D a ta \ N io b iu m D 8 3 m m P r1 .sto m e a s Load Dcalc. Show Init. Load Reset x3 y3 Stop Length P in tube C u r 1 8 .9 2 9 7 .5 0 data c a lc u Save Cut Zero Save Dcalc. 1 0 7 .8 1 0 0 .0 8Feb2000 Date PROCESS START 8 0 .0 2:20 Time Pscale 0.80 6 0 .0 P tu b e m a x 170 P in tube K Pstart 0 .9 4 0.5 P ze ro 1 4 .9 K P sta b 0 .9 9 4 0 .0 Pressure-axial displacement d P c o r.% 0 .0 Pstab 93.6 2 0 .0 Length, mm 0.10 dL L ze ro 7 2 .1 6 25.76 0 .0 gr3 -0 .1 2 .0 4 .0 6 .0 8 .0 1 0 .0 1 2 .0 1 4 .0 1 6 .0 1 8 .0 2 0 .0 2 2 .0 2 4 .0 2 5 .8 L teor 25.66 6 5 .0 m e a s Pcylinder D c a lc 6 2 .5 c a lc u P c yl m a x 130 0 4.4 0 .0 0 2 5 .7 5 6 0 .0 0 P c ylze ro -1 9 .6 4 2 .0 0 2 5 .2 2 5 7 .5 5 6 .5 0 2 4 .7 0 5 5 .0 41.70 41.70 R 1 R 2 6 5 .0 0 2 4 .1 7 5 2 .5 Radius, mm 7 0 .5 0 2 3 .6 5 0.00 d R 5 0 .0 41.70 7 5 .5 0 2 3 .1 2 4 7 .5 R te o r 4 1 .7 5 8 3 .5 0 2 2 .0 7 Radius-axial displacement 4 5 .0 9 0 .0 0 2 1 .0 2 Data T im e P tu b e L , m m R ,m m P c yl 4 1 .7 0 9 7 .5 0 1 8 .9 2 0 .8 4 .3 2 5 .8 4 1 .7 3 .1 gr2 -0 .1 2 .0 4 .0 6 .0 8 .0 1 0 .0 1 2 .0 1 4 .0 1 6 .0 1 8 .0 2 0 .0 2 2 .0 2 4 .0 2 5 .8 0 0 1 .5 0 1 6 .8 2 2 .8 4 .6 2 5 .8 4 1 .7 3 .1 x2 y2 Length Radius C u r 1 1 .6 9 5 0 .5 4 FEM Simulation 0 4 .0 0 1 4 .7 1 t0 5 2 2 6 6 8 5 0 0 0 b e g 3 9 9 .3 7 1 8 .2 7 T p a u se , m se c C o m m e n ta ry 0 6 .5 0 1 2 .6 1 0 . y1 P in cylinder Niobium 137*83.0*2.6mm. L0=51.6. e n d 1 0 0 0 .5 0 2 8 .5 7 0 7 .0 0 1 0 .5 1 of the 1 0 0 .0 0 Drossel=300, kran on -8, kran off 135. 0 6 .0 0 8 .4 1 Niobium tube Pr1. During of 8 0 .0 0 0 5 .0 0 6 .3 1 hydroforming (18-6mm of length) the hydroforming 6 0 .0 0 shape was conical, dD=5mm). Smooth 0 3 .0 0 4 .2 0 surface, inside and outside. Calibrated 0 1 .0 0 2 .1 0 4 0 .0 0 at 560bar. Thickness at equator 9 9 .0 0 0 .0 0 =2.2mm. 2 0 .0 0 0 .0 0 0 .0 0 0 .0 0 0 .0 0 0 .0 0 gr1 1 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 0 1 8 0 0 2 0 0 0 2 2 0 0 2 4 0 0 2 5 3 6 Front panel of the software for hydroforming - machine PC control allows reproducibly repeat the forming parameters W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
All steps of hydroforming optimized and checked on the Cu dummies Hydroforming of cells can be done or as three cells simultaneously or cell by cell (hydroforming of the 9-cells from one tube piece can be done on the same way) W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Some ideas contributed to hydroforming success Tube Movable Matrix Fixed Matrix Ptube sensor Water Hydr. system Oil Hydr Pcyl system Lsensor Rsensor sensor Synchronization mechanism for multi cell fabrication by hydroforming Developed ideas summarized in the patent. W.Singer, I.Jelezov; No. 10 2007 Nonsymmetrical mould 037 835 ; 18 September 2008 for hydroforming W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Fabrication steps of 9 cell cavity by hydroforming as option 3x3 W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
Z145: 9-cell as 3x3 cell cavity hydroformed at DESY, completed at E.ZANON (reached ca. 30 MV/m). Two new 9-cell cavities are currently in completing at E.ZANON W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA
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