Mechanics of superconducting magnetic bearings

In this dissertation, the static and dynamic characteristics of passive superconducting magnetic bearings using high-temperature Type-II superconducting ceramics are studied. Emphasis is on the magnetic-force interactions between permanent magnets and bulk high-temperature Type-II superconducting ceramics in the mixed state. The results derived from this study can be applied to electromechanical devices using high-temperature superconductors as force-generating or vibration-eliminating elements.; Levitation forces and lateral forces in relation to the gaps in superconducting bearings were measured using a beam-and-camera system. Dynamic magnetic stiffness derived from vibration tests were compared to static magnetic stiffness. The relaxation of magnetic forces as a function of time was measured as well. The behavior of levitation forces at temperatures form 4.2 K to 77 K were studied. A rotor equipped with two superconducting bearings was fabricated and was spun up to 120,000 RPM. The drag torques acting on the rotor were measured at bot atmospherical pressure and at a partial vacuum of a few mm Hg.; Many high-temperature superconductors of different compositions of fabricated through different processing techniques were investigated by measuring the magnetic force-gap relationships. The data indicated that YBa{dollar}sb2{dollar}Cu{dollar}sb3{dollar}O{dollar}sb7{dollar} specimens made of melt-quench process produced the largest magnetic forces obtained in the laboratory so far.; Models predicting the magnetic forces between superconductors and externally applied magnetic fields were studied. A numerical scheme based on the magnetization model was developed. The calculated levitation force-gap relationships showed a reasonable agreement with experimental results.