Article
Fatigue degradation of the current-carrying capacity of HTS-2 tapes during cyclic perpendicular compression
A. V. Krivykh
NRC «Kurchatov Institute», Pl. Akademika Kurchatova, 1, 123182, Moscow, Russia
e-mail: krivykh99@gmail.com
V. V. Guryev
NRC «Kurchatov Institute», Pl. Akademika Kurchatova, 1, 123182, Moscow, Russia
e-mail: guryevvv@mail.ru
K. V. Moseev
NRC «Kurchatov Institute», Pl. Akademika Kurchatova, 1, 123182, Moscow, Russia
Abstract
The effect of cyclic perpendicular compression on the current-carrying capacity of second-generation composite HTSC tapes (HTSC-2G) under conditions simulating the resource loads of conductors of the electromagnetic system tokamak is investigated. The main attention is paid to the fatigue degradation of the critical current after 50000 loading cycles, a mode that reproduces the long-term operation of the inductor winding. Samples of four types of HTSC-2G tapes with different architectures were tested in a liquid nitrogen medium at pressure of 100 and 150 MPa. It is shown that in three tape stacks without copper gaskets, the degradation of the critical current reaches 50% after 100 compression cycles 150 MPa. The use of additional copper tapes in the package decline degradation. The key result is the detection of significant (15–35%) degradation of the critical current of all tested architectures after 50000 cycles at a relatively low pressure of 100 MPa, relevant for the central solenoid. A counter-intuitive effect has been established: HTSC-2G tapes with additional tinning, demonstrating maximum degradation under single compression, exhibit the greatest tolerance to cyclic loading — their degradation does not exceed 20% over the entire studied cycle range (100 MPa), which is presumably due to the damping effect of the solder layer. The data obtained indicate that it is unacceptable to focus the design of superconducting magnets
solely on the critical current of a short sample without taking into account the cyclic resource.
Keywords: electromechanical properties; composite HTSC-2G tapes; nitrogen temperature (77 K); perpendicular cyclic compression.
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