Problems associated with the use of high purity aluminum in the design of composite conductors in the elasto-plastic region

High purity aluminum can apparently be used at high strain levels due to an anomalously low resistivity. However, the mechanical properties of aluminum strained to 0.003, which is unavoidable in large magnets, lead to extensive conductor confinement and support problems. High purity aluminum yields at 800 to 1200 psi which corresponds to a strain level of 0.0001 to 0.00017 at which point it becomes elasto-plastic with a small tangent modulus of approximately 0.2 × 10⁶psi. In this region excessive plastic flow is opposed only by slight amounts of work hardening. New annular finite elements are reported for the stress analysis and strain limiting designs are given which may allow for the use of high purity aluminum in large magnets. Conceptual designs for large energy storage magnets are proposed. Experimental work is in progress; preliminary data are reported.