Abstract: Objectives:To address the issue of low magnetic induction intensity and insufficient renewal of magnetic abrasive particles in magnetic abrasive finishing (MAF) of pipes, which results in low inner surface machining efficiency.


Methods:This paper proposes a novel method to enhance the finishing process. This method utilizes an optimized Bilateral Halbach array magnetic pole structure to improve the magnetic induction intensity and gradient within a confined space. Firstly, finite element software was used to analyze the magnetic field distribution of various magnetic pole structures. The Bilateral Halbach array magnetic poles were found to produce a stronger single-peak magnetic field in the machining area compared to other magnetic pole structures. Secondly, theoretical and simulation models were employed to identify the auxiliary magnetic pole height and thickness as sensitive parameters affecting the magnetic induction intensity and gradient of the Halbach array magnetic poles. These parameters were then used as optimization variables. Neural networks were utilized to fit the predictive model, ensuring accurate representation of the relationship between these parameters and the resulting magnetic field characteristics. The Non-dominated Sorting Genetic Algorithm Ⅱ (NSGA-Ⅱ) was applied to the predictive model to seek the Pareto optimal solution set, thereby determining the optimal configuration of the Halbach array. The use of NSGA-Ⅱ allowed for the simultaneous optimization of multiple objectives, ensuring that the final design provided a balance between high magnetic induction intensity and gradient. This optimal configuration, combined with the radial reciprocating feed of the magnetic poles, aimed to increase grinding pressure while simultaneously enhancing the turnover and renewal of the magnetic abrasive particles. Finally, the performance of different magnetic pole structures at two different rotational speeds was validated through simulations and experimental tests. The magnetic abrasive particle dynamics were simulated to provide insights into their behavior under varying conditions, while experimental tests confirmed the practical applicability of the theoretical and simulation findings.


Results:Experimental validation demonstrated that the optimized Bilateral Halbach array magnetic poles effectively increased magnetic induction intensity and gradient. Compared to the traditional N-S pole structure, the maximum magnetic induction intensity increased by 60%, and the magnetic field gradient improved by -30 mT/mm. The magnetic brush within the pipe exhibited stronger agglomeration strength, leading to higher processing efficiency. After 30 minutes of processing, the inner surface roughness of the pipe decreased to Ra 0.068 μm. The inner surface's oxide layer and original defects were completely removed, leaving only uniform transverse machining marks. The efficiency of the MAF process was improved by 90%.


Conclusions:The MAF process efficiency was improved by 90%, demonstrating the substantial benefits of the optimized Halbach array. The higher grinding pressure and more frequent turnover of the magnetic abrasive particles led to faster and more effective material removal, enhancing the overall efficiency of the finishing process. The optimized Bilateral Halbach array magnetic pole structure effectively enhanced the magnetic induction intensity and gradient within the pipe, leading to significant improvements in the efficiency and quality of the MAF process. During the finishing process, the magnetic brush inside the pipe exhibited high agglomeration strength, reducing the loss of magnetic abrasive particles and increasing grinding pressure. The frequent turnover and renewal of the magnetic abrasive particles extended their lifespan, ensuring consistent grinding efficiency and achieving a high-quality surface finish.