Theory analysis of critical-current degeneration in bended superconducting tapes of multifilament composite Bi2223/Ag

We investigated the stress–strain relation and the applied strain dependence of critical current I c(ε app) of high-strength Bi2Sr2Ca2Cu3O10+δ (Bi2223) R&D tapes reinforced by ~100-μm-thick Ni-based alloy sheets with various pre- tensions F pre applied during a lamination process. We confirmed that the thickening of Ni-alloy laminations is useful to enhance Young’s modulus compared with commercial tapes (≈30-μm-thick laminations). I c(ε app) decreases gradually and reversibly with applied strains ε app and then degrades irreversibly with larger tensile and compressive strains. The reversible strain regime tends to shift towards the tensile side with larger F pre, indicating that application of large F pre is effective to improve the reversible tensile strain limit. Observed I c(ε app) can be reproduced well by the model considering an ε app-linear critical current density, a cross-sectional strain distribution, and a Weibull-type distribution of filament damages. We clarified that different irreversible I c(ε app) degradations with large tensile and compressive strains can be understood by differences in the dimension and number of cracks and ruptures (tensile strains) and bucklings (compressive strains).

Section: Discussion On Gradual εApp-linear Ic Decrease In Reversible ...mentioning

confidence: 99%

Mechanical and critical current characteristics of high-strength Bi 2 Sr 2 Ca 2 Cu 3 O 10+δ multi-filamentary tapes reinforced with thicker Ni-alloy laminations with various pre-tensions

Okada

Kobayashi

Sakai

et al. 2022

“…The high intensity heavy ion accelerator facility being constructed at the Institute of Modern Physics of the Chinese Academy of Sciences will use a series of low-temperature superconducting (LTS) and high-temperature superconducting (HTS) magnets to guide heavy ions adiabatically [10]. However, because (i) both LTS and HTS materials are sensitive to stress and strain and (ii) excessive stress and/or strain can degrade the superconducting properties [11][12][13][14][15][16][17][18][19][20][21][22][23][24] and even cause a failure of superconducting magnet [25][26][27][28][29][30][31], it is important to limit deformation of a superconducting magnet so that it can withstand the large and/or variable electromagnetic forces and thermal stresses that arise at low temperatures and in strong electromagnetic fields [32][33][34][35][36][37][38][39][40]. Thus, the efficient operation and protection of superconducting magnets benefit from intelligent methods of strain detection.…”

Section: Introductionmentioning

confidence: 99%

A dynamic strain-based quench-detection method in an LTS sextupole magnet during excitation and quench

Gao

Guan

Xin

2020

Self Cite

The dynamic strain characteristics and responses of a low-temperature superconducting (LTS) magnet during excitation and a quench are investigated in the present work. For the strain measurements, strain gauges in the form of a half-bridge circuit comprising cryogenic strain gauges and their dummy resistances are embedded directly within the superconducting magnet structure. A wireless high-speed data acquisition system with a resolution of 1 ms is also used to obtain the strain history of the LTS magnet during operation. The dynamic strain induced by thermal or mechanical disturbances is detected promptly and compared with the transport current and temperature signals recorded during a quench. This indicates that the dynamic strain measured in the LTS magnet can capture a quench feature in a timely manner. For a better understanding of the dynamic strain histories in the magnet, the dynamic strain signals are subjected to spectral analysis during the excitation and pre- and post-quench processes. It is shown originally that several spectral peaks on strain measured are always observed at the onset of a quench. Thus, the dynamic strain characteristics and responses provide a evaluation means of superconducting magnet.

“…In the past decade, some empirical formulae and analytical solutions have been proposed to characterize the strain dependence of the electromechanical properties of Bi-2223/ Ag multi-filamentary HTS tapes [22][23][24][25][26][27][28][29][30][31]. The reversible degradation of I c in deformed Bi-2223/Ag multi-filament HTS tapes is likely to be related to the gliding of Bi-2223 grains [32] and grain boundary weak links [33,34].…”

Section: Introductionmentioning

confidence: 99%

“…Linear strain dependence of I c was widely adopted to characterize the reversible strain dependence of I c [22][23][24]. Some modeling approaches based on the Weibull distribution probability function have been reported to evaluate the irreversible degradation properties of I c [25][26][27][28][29][30][31]. Norris' formula [35] is usually used to evaluate the AC loss in superconductors for a certain operating current.…”

Section: Introductionmentioning

confidence: 99%

Strain dependence of critical current and self-field AC loss in Bi-2223/Ag multi-filamentary HTS tapes: a general predictive model

Gao

Wang

Zhou

2019

Self Cite

It is well known that mechanical deformations have a strong impact on the critical current (I c ) of Bi-2223/Ag multi-filamentary high-temperature superconducting (HTS) tapes, and a remarkable I c degradation is induced, which results in a significant AC loss. In this paper, a general predictive model based on the strain dependence of the Weibull distribution function of statistical damage of superconducting filaments and the Norris formula is developed to explore the influence of the uniaxial, bending and torsional deformation on I c degradation and self-field AC loss of Bi-2223/Ag HTS composite tapes. A unified strain dependence of the I c formula is suggested, which is extended in view of the I c degradation mechanism of Bi-2223/Ag HTS tapes under a uniaxial deformation with an introduction of longitudinal strain to unify the strain in uniaxial, bending and torsional deformation modes. Then, a modified Norris formula is deduced in light of the unified strain dependence of the I c model to predict AC loss of Bi-2223/Ag HTS tapes. With a set of appropriate model parameters determined by the tested data of I c under uniaxial deformation, the presented model can well predict both I c degradation and AC loss behaviors under not only a uniaxial deformation mode, but the bending and torsional ones. The proposed model indicates that the significant increase of AC loss for a deformed tape is presented due to the notable degradation of I .