Superconducting magnets experience very high forces as a result of the high magnetic fields involved. Design engineers need to know the strength of individual magnet components as well as assemblies comprising superconducting wires and the insulation systems involved.
The temperature range, from a peak during manufacturing down to operational temperature in liquid helium, is over 350 degrees Celsius. The different materials involved in the magnet expand and contract at different rates, polymers contract at higher rates than the metallic materials involved.
The magnet structure is typically impregnated with a polymer such as epoxy resin, chosen for low viscosity, long pot life and high toughness. The polymer exhibits both contraction as it hardens, as well as contraction when it cools. In addition, the stiffness drops by a factor of up to one hundred times above its glass transition temperature when compared to below.
Miniature tensile samples are used to test tensile propertes of a material
A reverse-cage rig is used for its compressive properties
A Dynamic Mechanical Analyser can be used to measure thermal contraction and stiffness against temperature
Written by Simon Canfer,
Composites and Materials Testing Group Leader.
