A two-dimensional (2D) axisymmetric finite-element model was proposed to simulate the levitation characteristics of a radial-type high-temperature superconducting (HTS) bearing. The E-J power law together with an H-formulation was used to consider the superconducting state. The numerical model was successfully implemented using a FORTRAN program. A comparison of the experimental results with the simulation was given to validate the model. It shows that they have good agreement. The electromagnetic behavior inside the HTS bulks was also analyzed. The model presented in this paper can be used to optimize the design of a radial-type HTS bearing.

We established a 3D coupled model to study the electromagnetic-thermal behaviors of a levitation system containing a bulk high-temperature superconductor (HTS) with a cuboid slot under the nonuniform magnetic field due to the movement of a permanent magnet (PM), analysing the influences of the geometrical parameters of the slot and inclination angle on the electromagnetic-thermal behaviors, giving the dynamic distribution of the global electromagnetic force density in the HTS. The results show that the longer the length of the slot, the smaller the levitation force, and the greater the loss. As its length takes up 7/10 of the HTS diameter, the loss is 4 times that of the HTS without damage. Due to the homodromous induced current appearing near the slot, the maximum guidance force increases with the length. The levitation force decreases with the increase of the slot depth. Its curve near the maximum becomes blunt and the loss increases significantly. As the depth is 3/5-4/5 of the HTS height, the loss is 300–400 times of that without damage. The guidance force and loss increase with the depth. As the inclination angle rises, the levitation and guidance force both drop. At 30 °, their maximums decrease by 70 % and 90 %, respectively. The lateral stability of the system thus becomes poorer, indicating the inclination angle is one of the important factors for instability. As the PM moves vertically, the guidance force density symmetrically distributes near the both wide sides of the slot. Its side faces with the wide sides will bear the shear force, resulting in that the slot has the tendency to tear along these faces. As the PM reciprocates laterally, the slot is subjected to the lateral shear force, proportional to the displacement.

The surface micro-dimple arrays can effectively improve the friction and lubrication performance of moving parts and are widely used in cutting tools and mechanical transmissions. Through-mask electrochemical machining (TMECM) is a process that uses the anodic dissolution principle to remove materials at low temperatures. It is suitable for efficiently processing large-area micro-dimple arrays on metal surfaces. However, the previous TMECM method still suffers from the problem of low processing adaptability. In this paper, a new method for scanning-cathode TMECM by utilizing the fluid dynamic pressure effect was proposed, and the flow field and electric field models of various inner-jet cathodes were developed as well. Through numerical simulations of the flow field and electric field, the flow velocity, electrolyte pressure, and current density distributions for different inner-jet cathodes were investigated to determine an appropriate cathode. Contrasting experiments were conducted to investigate the variations in electrolyte flow states and machining currents for different inner-jet cathodes. Additionally, the changes in micro-dimple dimensions under different machining parameters were investigated. Moreover, the micro-dimple arrays of 385.7 μm in diameter and 111.8 μm in depth, 288.8 μm in diameter and 40.3 μm in depth, and micro-dimple arrays with an etching factor of 1.69 were fabricated, and the results demonstrated the good processing adaptability of the scanning-cathode TMECM.

Currently, copper-oxygen high-temperature superconducting materials have strongly anisotropic electromagnetic properties, which are difficult to describe in the equations. And in the rotating machine containing the permanent magnet (PM) rotor and bulk high-temperature superconductor (HTS) stator, when the HTSs have defects, their electromagnetic-stress behaviours may affect the mechanical stability of the equipment and even cause it to not work properly. In this paper, we proposed an anisotropic electromagnetic equation based on the H-formulation and established a three-dimensional coupled model with the magnetic, thermal and stress fields to study the electromagnetic-stress behaviours of a HTS with a slot defect during the swing of a PM, discussing the effects of the interior angle and inclination angle of the defect on the behaviours. The results show that the interior and inclination angles of the defect have a large influence on the electromagnetic-stress behaviours. For the electromagnetic characteristics, the main influence is on the rotational losses. Especially the losses at an inclination angle of 60° are 16.5 times those without damage. This is related to the ‘thin wall’ structure near the upper surface of the HTS. The stress concentration point appears on the defect boundary. The novelty of this paper is the proposal of the anisotropic electromagnetic equations based on the H-formulation and the study of the electromagnetic-stress behaviours of a superconducting swing system containing a PM and HTS with a slot defect from a three-dimensional perspective. The research results of this paper can be the references for the design and structural protection of superconducting rotating machines.