The tensile property of commercial Bi2223 tapes: a report on the international round-robin test

Abstract

In order to establish the test method of mechanical properties of oxide composite superconductors, an international round-robin test (RRT) has been carried out under the programme of VAMAS activity, for which eight research groups participated. The present RRT made the following guideline clear for assessing the mechanical property of Ag/Bi2223 multifilamentary tapes. Owing to the constitution of the brittle superconductive oxide layer embedded in the ductile metal matrix, the stress–percentage extension (R–A) curve shows a three-stage behaviour, that is, the true elastic region is very narrow and is followed by the quasi-elastic region before reaching the macroscopic plastic region. For assessing the elastic constant, it is recommended to look for the maximum slope carefully by enlarging the initial part of the R–A curve. The following three quantities, elastic constant, yield strength and tensile strength, can be reasonably determined with good accuracy by the procedure reported in this paper. The percentage extension after fracture is, however, excluded from the standard procedure, because it scatters to a great extent owing to the nature of the test sample as well as the experimental limitation.