1. Modeling of LTS and HTS superconductors at the University of Twente
K. ILIN1, K.A. YAGOTINTSEV1, M. DIJKSTRA1, C. ZHOU2, V.A. ANVAR1, W.A.J. WESSEL1, J. KOSSE1, S. OTTEN1, T.J. HAUGAN3, D.C. VAN DER LAAN4, A. NIJHUIS1
1 University of Twente, Faculty of Science & Technology, 7522 NB Enschede, The Netherlands; 2 ITER Organization, France; 3 US Air Force Research Laboratory, Wright Patterson AFB, OH 45433, USA; 4 Advanced Conductor Technologies and University of Colorado, Boulder CO 80301, USA
3-A3LS-O1.4
Intra-strand resistance simulation and measurements
Stress-Strain FE modeling of REBCO tapes
Cabled conductor optimization
Single tape modeling steps
Simulation and results: Intra-strand resistance
Tensile
Torsion
Transverse
Experiments
Parametric studies on cabled conductors are time consuming and expensive
Cable model
For optimization of manufacture and operating conditions (ABAQUS and COMSOL)
Validation
Of electro-mechanical REBCO model by experimental data
Optimization
Optimal choices for tape and cable geometry - materials
Tape Superpower SCS4050:
- Substrate (Hastelloy C-276)
- Copper (Electroplating)
- REBCO
We use elasto-plastic material properties depending on temperature to model the production process.
Model: residual strain in REBCO layer at room temperature –0.17 %.
Cooling down to 77 K increases compressive strain further to ~ –0.24 %.
Overview of the filament-to-matrix contact resistivity R (m2 ):
NbTi: ~ 5×10-15; Nb3Sn: 1×10-15 ~10-14 ; MgB2 : ~ 1-6×10-12 ;
BSCCO: ~ 3× ×10-13 ; ReBCO: ~ 1×10-14
Single tape modeling results a b
Tensile load
Combined
torsional-tensile load
Transverse load
Good agreement with transverse resistivity obtained from AC coupling loss
Tape. Experiment (77K)
Tape. FEM (77K)
Tape. Experiment (RT)
Tape. FEM (RT)
FEM simulation: Tensile – Torsion at 77 K, with longitudinal strain in REBCO layer
Simulations and results of current transfer length
Comparison of the tensile experiments with modeling results for the tape at RT and 77 K.
The FE mesh of the tape, anvil and pushing head, and boundary condition.
Longitudinal strain in ReBCO layer calculated using 100 µm copper thickness.
Critical stress and strain under tensile load at 77K (FEM, experiment).
Thickness profiles of 2G Superpower® 4050 tape with different copper layers.
FEM computation: instant of critical strain in ReBCO layer as a function of applied external tensile strain and applied torsion strain at 77K.
Experimental results based on Ic measurement with 10 μV/m criterion (less sensitive with increasing torsion).
Critial stress (MPa)
Critical strain (%)
Experiment
864
0.67
FEM (ABAQUS)
883
0.70
FEM (COMSOL)
874
0.69
Critical force as a function of copper layer thickness at 77K. FEM model and experimental results.
CORC cable modeling
CORC cable FE modeling: Bending
CORC cable FE modeling: Winding and cooling
Cable bending radius
R = 200 mm
εirr = 0.45%
Critical strain level
Residual strain after the production process of the tape(RT)
Strain after the winding (RT)
Longitudinal strain in the YBCO layer along the transverse path after the cool-down to 77K with varied thermal expansion coefficient of the core tube (α)
α = 0.25· /K
α = 0.50· /K
α = 0.75· /K
α = 1.00· /K
α = 1.25· /K
α = 1.50· /K
α = /K
α = 1.75· /K
α = 2.00· /K
Cool-down to 77 K. Longitudinal strain in the YBCO layers.
Transverse path
Step 1
Tape production (var Tproc)
Step 2
Tape winding to CORC at RT
Step 3
CORC bending to coil at RT
Step 4
Cooling to operating Top (77 K)
Step 5
Electromagnetic load at Top
Strain along the tapes direction in the REBCO layers at the moment the cable radius R = 200 mm and friction coefficient μ = 1.
With the analytical formulae and the extracted intra-strand resistance, the calculated λ amounts to 0.26 mm (x=0.5 mm) and 2.3 mm (x=15.9 mm), in good agreement with the experiments.
UT strand model: 2012 Supercond. Sci. Technol
Bending R for ε = 0.45% versus friction coefficient.
For μ = 0.2 and 0.3 no convergence reached in computation.