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Free-form surface is widely applied in the manufacturing industries due to its excellent geometric characteristics. Surface finishing of free-form surface is a critical manufacturing process to meet the target quality requirement. In this work, a magnetorheological shear thickening finishing (MSTF) method was employed with the designed finishing tool and the developed MSTF media for the finishing of a typical free-form surface, i.e., Sine surface. The finishing tool was designed as a slotted cylindrical permanent magnetic pole with radial magnetization. The magnetic pole was fabricated to dominate MSTF performance of the finishing media. To obtain sufficiently large magnetic flux density and magnetic field gradients in the finishing zone, finite element analysis (FEA) was used to optimize the dimension of the finishing tool. The MSTF principle was illustrated in detail. The mathematical model of the material removal was established. Finishing experiments were conducted on the SUS304 Sine surface using the developed MSTF media. The effects of finishing parameters on surface roughness were evaluated quantitatively. The results showed that the material was uniformly removed across the entire Sine surface with over 87% improvement in surface roughness (Sa). It is quite potential for the surface finishing free-form surface in a wide manufacturing industrial applications.

Efficient and high-precision magnetic grinding technology has become a bottleneck technology for the manufacturing and repair of high-performance aircraft engines. Previous studies have mostly focused solely on quality control to determine the effectiveness and feasibility conditions for optimizing the design of magnetic pole grinding devices. This method is far from meeting the needs of precise and efficient magnetic grinding of the inner surface of aircraft engine bent pipes. This article introduced the method and mechanism of precision magnetic grinding of the inner surface of aircraft engine bent pipes. This article proposed the optimization theory of permanent magnetic pole taper structure based on auxiliary slotted magnetic pole structure and the finite element model of magnetic pole taper of slotted auxiliary magnetic pole structure. This article summarized the influence of the taper of permanent magnetic poles based on auxiliary slotted magnetic poles on magnetic grinding and summarized the evaluation method for the optimization effect of magnetic grinding devices. This article listed the application of magnetic pole device optimization in precision magnetic grinding of the inner surface of aircraft engine bent pipes. This article provided an outlook on the development trend in precision magnetic grinding magnetic pole devices for the inner surface of aircraft engine bent pipes. The conclusion was drawn that establishing a three-dimensional discrete finite element model based on slotted magnetic poles can improve the accuracy and efficiency of magnetic research.

— A new approach is proposed to calculate the instantaneous velocity of magnetic poles. The method uses the spatial distribution of the vector of the horizontal component H , calculated from analytical models of the main geomagnetic field for the current and the nearest epochs. The horizontal component was calculated using the coefficients of two models: IGRF 13 and COV - OBSx 2. The equation for the velocity of pole movement is obtained from the condition that the horizontal field component at the pole point is equal to zero at any moment in time, which allowed us to determine the directions of instantaneous velocity. To find the position of the pole and the velocity of its movement between epochs, it is proposed to use a hermitian spline, which describes a smooth curve, whose tangent coincides with the velocity vector in each epoch. It is shown that the velocity vector of the pole movement depends linearly on the derivative of the horizontal component with respect to time and is inversely proportional to the derivative of H with respect to coordinates. It has been established that higher harmonics are primarily responsible for the acceleration of the pole movement. This is due to their significant contribution to the horizontal component in the polar regions. The obtained instantaneous velocities were compared with the average or interval ones, which are determined from the position of the pole for neighboring epochs. When using the IGRF 13 model to calculate the coefficients, artifacts were found in the trajectory of the poles: large deviations in both the directions and magnitudes of the instantaneous velocity vectors compared to interval ones. For the COV - OBSx 2 model, no such artifacts were found. It has been assumed that the observed systematic differences in the vectors of instantaneous and interval velocities calculated using the IGRF 13 model are associated with the methodological features of constructing this model. In particular, the interval between generations of the IGRF 13 model is 5 years, while for the COV - OBSx 2 model it is 2 years and splines were used to construct the latter model. It is noted that the direction of interval velocities for these two models can differ by 40°. Limitations on the applicability of the method associated with sudden changes in the trajectory of the pole are determined. In this case, the method may be unstable, since when calculating the time derivatives of the field at a given epoch, models of the nearest epochs are used. In the case of sudden changes in the pole trajectory, the values of these derivatives strongly depend on the chosen method of numerical differentiation with respect to time. For the reliability of the proposed method, it is required to know the geomagnetic field in the vicinity of the pole at time intervals shorter than those in the IGRF 13 model.

Magnetic abrasive finishing (MAF) is an effective surface finishing method. At present, most of the research on plane MAF focuses on finishing characteristics. However, due to the “edge effect” of the magnetic field and the rotational movement of the magnetic brush, the uniformity and flatness of the finished surface are poor. In order to further improve the accuracy of the finished surface, the surface uniformity and flatness are improved by changing the shape of the magnetic pole and the trajectory of the magnetic brush. At the same time, the surface flatness is evaluated not only by the maximum height difference of the cross section but also by the standard deviation to evaluate the surface uniformity and flatness. Through magnetic field simulation and experiments, it is proved that the bottom groove of the magnetic pole helps to make the magnetic particle distribution more uniform in the processing area, which can effectively improve the surface quality. In addition, through experiments, changing the trajectory of the magnetic brush can also effectively improve the surface flatness of the finished surface.

Purpose The purpose of this study is to propose an optimized magnetic pole design for AFPM motors to address the issues of low permanent magnet utilization, non-sinusoidal air gap flux density and inefficient use of axial space, thereby enhancing power density under the constraint of a constant permanent magnet volume. Design/methodology/approach In this paper, a semiinserted three-segment double-layer magnetic pole structure is proposed for the dual-rotor single-stator AFPM motor. First, the effects of rotor core reduction and permanent magnet insertion on the performance of the motor are compared. Considering the output torque, magnetic field distribution, manufacturing process and other factors, the optimal permanent magnet insertion thickness is selected and the utilization rate of the axial space of the motor is optimized. Second, the semiinserted permanent magnet is divided into three sections with equal ring width along the radial direction, and then each section is divided into an insertion layer and a surface-mounted layer. The spatial distribution of the permanent magnet and the shape of the rotor surface core are optimized by changing the pole arc coefficient of each section and each layer of the permanent magnet. Finally, the advanced Latin hypercube sample method is used to analyze the sensitivity of the magnetic pole parameters that need to be optimized, and the adaptive metamodel of optimal prognosis method is used to optimize the magnetic pole parameters. Findings Compared with the original motor, the volume is reduced by 6.2%, the average output torque is increased by 7.4%, the torque ripple is decreased by 73.9% and the power density is increased by 14.5%. Originality/value The proposed pole structure can reduce the axial length of the motor, improve the utilization rate of the permanent magnet and suppress the torque ripple. It has important engineering value in reducing the cost and volume of the motor.

Axial flux permanent magnet motors (AFPM) are optimal for hub drives in electric vehicles due to their compact size and high power and torque density. However, the surface-mounted pole structure of the AFPM is susceptible to significant eddy current losses, which can result in irreversible demagnetization of the poles. Furthermore, hub motors for electric vehicles require superior electromagnetic performance. In order to comprehensively consider the eddy current losses and the electromagnetic performance of the motors, this paper proposes a novel topology of an unequal thickness segmented magnetic pole axial flux permanent magnet hub motor (UTSMP-AFPM). Firstly, a mathematical model of eddy current loss in the permanent magnet of an axial flux permanent magnet motor is derived theoretically. The mechanism of pole segmentation to reduce eddy current loss in the permanent magnet is analyzed, and an analytical formula for the electromagnetic characteristics of the motor is established. The performance of the motor is further optimized. Subsequently, finite element simulations are conducted to assess the permanent magnet eddy current loss, rotor temperature rise and electromagnetic performance of the proposed motor in comparison to that of the traditional YASA motor. Finally, a prototype is constructed and the proposed structure is validated through experimentation.

A new configuration of permanent magnet as a source of external magnetic field has been established to an autogenous tungsten inert gas (TIG) welding. The external magnetic field is generated by rectangle shape NdFeB permanent magnets of 260 mT and arranged in cups-type magnetic field (CMF). A charge-coupled device (CCD) is applied to monitor the phenomenon of the arc shape. The material used in this experiment is SS304 with a thickness of 2 mm. This study aims at investigating the effect of external magnetic field towards the arc shape and finding the configuration, which can reduce the power consumption and improve penetration. A significant effect on the improvement of welding efficiency can be achieved by using PR-NNSS-SD (50 or 70 mm), PP-NNSS-SD (70 or 90 mm), or PP-NSNS-Pull (50 mm). These configurations can reduce the power consumption up to 11%.

The dual-pole magnetic abrasive finishing (DMAF) method was proposed to achieve a smooth surface on TC4 titanium alloy. Firstly, both the distribution of the magnetic field and the intensity of magnetic induction produced by nine combinations of magnetic poles of different shapes were simulated using Ansys Maxwell software (2024R2). According to the results of the simulation, the optimal combination of magnetic poles was determined. Then, the machining parameters of multi-stage DMAF were optimized through comparative experiments on major single factors. Finally, combinations of the mixed magnetic abrasive in three polishing stages were obtained as follows: #100 electrolytic iron powder (Fe3O4) + #2000 white abrasive (WA), #200 Fe3O4 + #8000 WA, and #450Fe3O4 + #w1 diamond (DMD). The gap between the upper and lower magnetic poles was set to 5 mm, the rotational speed of the magnetic pole was set to 300 rpm, and the quality ratio of the abrasive was 2:1. The experiments indicated that the average surface roughness Ra was reduced from an initial value of 0.433 μm to 8 nm after 30 min of multi-stage DMAF, and a nano-level mirror polishing effect was essentially achieved in the polishing zone.

This work focuses on the small Bearingless Brushless DC Motor (BL-BLDCM), to solve the problems, such as larger commutation torque ripple and difficult solution of air-gap magnetic field, a novel BL-BLDCM structure with like-tangential parallel-magnetization interpolar magnetic poles (LTPMIMPs) is proposed, which is abbreviated as BL-BLDCM-LTPMIMP in this work, and the analytical calculation model of its air-gap magnetic field has been investigated. First, inserting a like-tangential parallel magnetizing auxiliary magnetic pole between every two adjacent single-radial-magnetizing main poles, and forming several combination magnetic poles, each of which is composed of a radial-magnetizing main magnetic pole and two semi-auxiliary-magnetic-poles (with different magnetization directions) located on both sides. Then, by solving the Laplace equation and Poisson equation in every subdomain, and combining the relative permeability function, the analytical expressions of the air-gap magnetic fields for the BL-BLDCM-LTPMIMP was obtained. The armature reaction magnetic fields of the torque windings and suspension windings are also analyzed. Finally, through the finite element method (FEM), the correctness and computational accuracy of the analytical calculation model for the air-gap magnetic field is proven. Additionally, the comparison of electromagnetic characteristics with ordinary BL-BLDCM shows that the BL-BLDCM-LTPMIMP can not only effectively improve the amplitude and stability of electromagnetic torque on the basis of obtaining a shoulder-shrugged trapezoidal wave air-gap magnetic field but also has stable radial magnetic levitation force control characteristics.

To reduce the iron loss and torque ripple of an external rotor consequent pole (ERCP) motor used in an electric vehicle air-conditioning compressor, the magnetic pole structure of the motor was improved, and an unequal piecewise consequent pole (CP) structure was designed. The performance of the motor is optimized by reducing the harmonic content in the air gap flux density and reducing the iron saturation degree of the motor. The designed CP structure can significantly reduce the iron loss and torque ripple of the motor. Based on the Taguchi method, the optimal size parameters of the unequal piecewise CP structure are determined, and the final optimization design scheme is obtained. The results of finite element simulation and high-precision iron loss model show the following: compared with the original motor, the iron loss and torque ripple of the motor with the final optimized design scheme are significantly reduced.