International round robin test for mechanical properties of Nb 3 Sn superconductive wires at room temperature

Self Cite

An international round robin test was promoted to establish a test method for room temperature mechanical properties of commercial REBCO superconductive tapes. Seven laboratories practiced a tensile test under the direction of guideline REBCO13 for four different kinds of REBCO tape. From the stress versus strain curve, the modulus of elasticity and the 0.2% proof strength were measured. The scatter of measured values was analyzed by evaluating the RSU (relative standard uncertainty). To judge the major contribution to scattering, an F test was applied. The major source of RSUs was estimated to be the influence of inter-laboratory scattering. In order to reduce the overall scattering, it is suggested that the REBCO13 guideline should be modified with respect to the following three experimental factors. The window determining acceptable data should be narrowed, and the initial strain rate should be suppressed to less than 1 × 10 −4 (s −1 ). Repeated thickness measurement is recommended to reduce the standard uncertainty.

Section: Qualification Testmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

International round robin test for mechanical properties of REBCO superconductive tapes at room temperature

Osamura¹,

Shin²,

Weiss³

et al. 2014

Self Cite

“…The results indicate that the residual strain of the Bi2223 in HIc sample is relatively small because of the small difference between d 0 and d. The difference between d 0 and d in HS is comparatively large, so that the compressive residual strain is probably present. Osamura et al performed an analysis based on the rule of mixture [10], and the same tendency was obtained by both HIc and HS.…”

Section: Diffraction Elastic Constantsmentioning

confidence: 67%

“…Using the Bi phase residual strain obtained by neutron diffraction, the thermally induced residual strain of Ag phase was estimated by the law of mixture model [10], because an accurate d for strain-free Ag was not obtained. The calculation was performed assuming that the yielding had not occurred in the Ag phase.…”

Section: Diffraction Elastic Constantsmentioning

confidence: 99%

In situstrain measurements by neutron diffraction and residual stress estimation in Ag-sheathed Bi2223 superconducting composite tapes

Machiya

Osamura

Suzuki

et al. 2008

Heretofore, an accurate residual stress in Ag-sheathed superconducting composite tape could not be obtained from a measurement using conventional low energy x-rays due to the large x-ray absorption in Ag phase. Therefore, we developed a method for evaluating the residual strain in the filaments using neutron diffraction and finite element method (FEM) analysis, measuring the mechanical curvature. As for the residual strain of the Ag phase and Bi phase in a high strength type specimen, the Bi phase has a compressive longitudinal strain, and the Ag phase has a tensile strain; these are thermally balanced residual stresses at room temperature that depend on the mismatch of the coefficient of thermal expansion (CTE). On the other hand, there was very little thermally induced stress at the room temperature in the high Ic specimen. The numerical residual strain obtained by the FEM analysis agrees with experimental neutron method results. In a high critical current (Ic) type specimen, the existence of a stress relaxation mechanism during the heat treatment is suggested.

“…A number of RRTs for tensile testing at room temperature have been already successfully completed for Nb 3 Sn [8], BiSCCO [9], and REBCO [10] wires. Following this experience, an international RRT for tensile testing HTS wires at cryogenic temperatures was promoted by the Versailles Project on Advanced Materials and Standards and supported by the International Electrotechnical Commission.…”

Section: Introductionmentioning

confidence: 99%

International round robin test for tensile testing HTS wires at cryogenic temperatures

Bagrets

Anvar

Chiesa

et al. 2019

Self Cite

Within the framework for establishing standards of test methods for superconducting technical wires, various standards have been issued by the International Electrotechnical Commission (IEC) (standard documents IEC 61788-1 to -20). Following the successful round robin test (RRT) for tensile testing REBCO wires at room temperature (Osamura K et al 2014 Supercond. Sci. Technol. 27 085009), this effort is extended to tensile test HTS wires at cryogenic temperatures and is coordinated by the CryoMaK lab at Karlsruhe Institute of Technology. Five different commercially available REBCO wires from five different manufacturers and one BiSCCO wire from another supplier were provided by the Versailles Project on Advanced Materials and Standards (http://vamas.org) for testing. Samples were distributed between eight participating labs from five different countries for testing according to the specified guidelines. After the test results were delivered by all participants, the data were evaluated with statistical tools to investigate the main source of scatter and its magnitude in the test results. The final goal of the RRT is issuing an ISO/ IEC standard for a cryogenic temperature tensile test for REBCO wires. In this report the results of the RRT for tensile testing REBCO wires at cryogenic temperatures are presented and discussed.