Mechanical behavior of Nb-Ti superconducting composites with copper matrices have
been studied experimentally and theoretically.
Experimental work includes extensive measurements of Cu/Nb-Ti composite system.
Techniques for fine fiber testing and composite wire measurement have been developed.
Experimental parameters examined in this research include geometry, hardness, Young's
modulus, Poisson's ratio, yield strength and ultimate strength. Three theoretical models
have been developed to study the mechanics of the Cu/Nb-Ti composite system. The
influence of several design parameters on the mechanics of the Nb-Ti composites was
studied and provides some insight on superconducting composite design for improvements
in processing and performance.
The mechanical behavior of the Cu/Nb-Ti composite system are found to be functions
of geometry, composition and processing.
Geometry of Nb-Ti superconducting composites is different from most engineering
composites and there are two factors affecting sample geometry: the variability of fiber
geometry and the placement of fibers within the composite. The strength distribution of
Nb-Ti fibers is closely related to the distribution of fiber geometry and the composite
strength increases as the scatter of fiber strength decreases.
Heat treatment reduces the hardness of the bulk copper dramatically. The first heat
treatment increases the strength and hardness of the Nb-Ti fibers, further heat treatments
reduce the strength and hardness while increasing Young's modulus of the fibers. As the
extent of cold work increases, the strength of Nb-Ti fibers and that of the composite wires
increases. Cold work effects on the Young's modulus of the composites and the Nb-Ti
fibers are not significant.
For a constant global Cu/SC ratio, the lower the local Cu/SC ratio, the lower the micro-in-plane stresses. From this point of view, the fibers should be packed as close as possible
to one another. For a constant local Cu/SC ratio, when the inner radius of the Nb-Ti
assembly increases (the fibers are packed further from center), the macro-in-plane stresses
increase. From this point of view, the fibers should be packed as close to the center of the
wire as possible.
For a constant geometry, the higher the difference between E[subscript f] and E[subscript m], the lower the in-plane
stresses, and the higher the difference of the Poisson's ratio between the
components, the higher the in-plane stresses. / Graduation date: 1995
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35007 |
| Date | 23 June 1994 |
| Creators | Guo, Zhiqiang |
| Contributors | Warnes, William H. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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