Design, Fabrication, and Testing of an Apparatus for Mechanical Properties Characterization of Nb3Sn Superconducting Wires.
Multifilament Nb3Sn superconducting wires are of interest for building high-magnetic
field superconducting magnets. The superconducting A15 phase Nb3Sn is formed after
applying one or more heat treatments with a temperature above 650°C. This phase is
very brittle and failure of the filaments occurs. This results in degradation of the
performance characteristics of the wire and the ... read moresuperconducting magnet. Finite element
analysis (FEA) is used to predict the behavior of a full-size cable comprised of
thousands of individual wires. Due to the complex composite structure of a wire and the
varying stages of plasticity of each material, mechanical property estimations such as
the rule of mixtures (ROM) are not accurate. Experimental tensile testing is required
for accurate measurements of the mechanical properties of the composite. This thesis
discusses the design, fabrication, and testing of a tensile testing apparatus for
characterizing the mechanical properties of Nb3Sn strands and cables. Measurements were
performed on Nb3Sn strands from different manufacturers at room temperature, but the
device has the capability of measuring properties of multi-strand cables and can be used
at cryogenic temperatures. From the stress-strain curves of the tested wires, the
following mechanical properties were evaluated: modulus of elasticity, proof strength,
tensile strength, and elongation to fracture. The scatter of the measured values was
analyzed to measure the COV, the standard deviation divided by the average, and compared
against similar superconducting wire tensile testing machines from
Thesis (M.S.)--Tufts University, 2012.
Submitted to the Dept. of Mechanical Engineering.
Advisor: Luisa Chiesa.
Committee: Gary Leisk, and Makoto Takayasu.
Keywords: Materials Science, and Mechanical engineering.read less