This paper outlines materials testing at cryogenic temperatures. The evaluation of standard mechanical properties of domestic materials is essential for designing cryogenic devices which are necessary for the development of fusion reactors, magnetic suspension trains, superconducting generators and so on. Typical examples of equipment and techniques used by various researchers in the field of cryogenic testing are described.
Superconducting magnets for fusion device are greatly influenced by the radiation environment and the principal radiation-induced trouble is to arise from the change of mechanical fracture behavior in organic materials used as insulating and/or potting materials. Small compression test specimens of epoxy resin are tested after gamma and pile irradiations at low temperatures. Three kinds of mechanical properties i.e. (a) breaking stress, (b) breaking strain and (c) elastic modulus are investigated. A statistical analysis of the data from a large number of small specimens revealed the followings: (i) The effects of gamma and neutron irradiations on the fracture behaviors are observed to be different. This fact suggests that the simulation study by gamma is not safe for neutron irradiation. (ii) In the case of reactor irradiation overall softening are induced accompanied by local hardening and embrittlement. A qualitative explanation to the above results is presented and their effect on the performance of the magnets is stated.