Design of an Evaluation System for Mechanical Properties Under Cryogenic Conditions Using HTS Coils

This paper proposes an Evaluation System for Mechanical Properties (ESMP) that utilizes the repulsive force between two horizontally placed high temperature superconducting (HTS) coils. The ESMP is designed to evaluate the mechanical properties of materials at cryogenic temperatures, with a maximum applicable tensile force of 40 kN. The Finite Element Method-based electromagnetic simulations were performed for HTS coil gaps ranging from 240 mm to 280 mm to derive relationships between operating current and repulsive force. A model-based current control scheme was developed using feedback from strain gauges, Hall sensors, and current sensors. The current control logic was designed based on the interpolation of simulation data to compensate for the increasing coil distance caused by specimen elongation. The ESMP was validated through simulations at 77 K and 4.2 K. This system offers a viable alternative to conventional cryogenic testing methods that rely on liquid helium. It is expected to contribute to evaluating materials of cryogenic equipment for carrier ships.