Evaluation of mechanical properties of high-temperature superconducting bulks fabricated by a melt-processing

High-temperature superconducting bulks with highly oriented crystallographic structures are expected to be applied for high field quasi-permanent magnets, current leads and so on. However, the bulks sometimes fracture due to the thermal stress on the cooling process or the electromagnetic force during the magnetization. Thus, it has been recognized that improvement and understanding of the mechanical properties of bulks are indispensable for practical application. In this review, we summarize the present status of evaluation process of the mechanical properties for various bulks. The Young's modulus, Poisson's ratio, fracture strength, fracture toughness and hardness are evaluated by tensile, bending, compression and hardness tests. The mechanical properties are anisotropic, mainly due to the crystallographic structure and pre-existing micro-cracks associated with it. Data obtained are summarized and the influential parameters associated with the microstructure and testing condition for the mechanical properties are explained.