Preliminary tests for determining the procedure of round robin test on tens
ile testing methods of Cu/Nb3Sn composite wires at room temperature have be
en conducted. Two kinds of bronze processed wires were used. The following
results were obtained.
(1) The initial part of the stress-strain curve was liable to be varied. Be
yond the stress level of about 80 MPa, stress-strain behaviors were basical
ly identical regardless of the gripping method and the inter-grip distance
although shifts in strain axis were inevitable. Pre-loading of about 40 MPa
was fairly effective for obtaining a consistent stress-strain behavior for
a wire.
(2) A reliable modulus of elasticity could be determined using unloading cu
rve regardless of the unloading stress level.
(3) The stress-strain curves could be expressed as a simple exponential fun
ction, which fitted the experimental data fairly well excepting initial par
t and was useful to determine the zero strain position of the curves.
(4) The 0.2% proof stresses with a coefficient of variance of less than 5%
could be obtained using the zero strain position and the modulus of elastic
ity. (C) 2001 Elsevier Science B.V. All rights reserved.