CFM 2019

Mechanical characterization of OFE-Cu at low and high strain-rates for SRF cavity fabrication by electrohydraulic forming
Jean-François Croteau  1, *@  , Elisa Cantergiani  1@  , Nicolas Jacques  2@  , Aboulghit El Malki  3@  , Gilles Mazars  4@  , Gilles Avrillaud  5@  
1 : I-Cube Research
I-Cube Research
2 : ENSTA Bretagne
ENSTA Bretagne, CNRS UMR 6027, IRDL, 2 rue François Verny, 29806 Brest Cedex 9, France
3 : MSN/LBMS  -  Site web
ENSTA Bretagne
2 rue François Verny 29806 Brest, France -  France
4 : Bmax  -  Site web
Bmax
30 Boulevard de Thibaud 31104 - Toulouse -  France
5 : Bmax
Bmax
30 Boulevard de Thibaud 31104 - Toulouse -  France
* : Auteur correspondant

In the framework of CERN's Future Circular Collider (FCC), fabrication of high-performance superconducting radiofrequency (SRF) cavities is crucial to attain energy levels relevant for breakthrough research in particle physics. SRF cavities, the components responsible for beam acceleration, are made of bulk niobium or of a copper substrate with a niobium coating. Damage of the inner surface of copper cavities must then be minimized to ensure proper growth of the niobium superconducting film and prevent quenching during operation. An alternative technique to traditional forming methods, such as deep-drawing and spinning, is electrohydraulic forming (EHF). In EHF, half-cells are formed through high-speed deformation of blank sheets, using shockwaves induced in water by a pulsed electrical discharge. The design of EHF processes requires the development of accurate, multi-physics numerical models. During an EHF operation, the material is subjected to high strain-rates. The proposed communication deals with the mechanical characterization of annealed oxygen-free electronic (OFE) copper at different strain-rates. The constitutive response in tension and compression of OFE copper has been investigated, for strain-rates ranging between 1x10^-3 and 4x10^3 s^-1. From the obtained experimental results, parameters for the Johnson-Cook constitutive model have been identified using the finite element software LS-Dyna, coupled with the optimization software LS-OPT.


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