小孔内表面磁力研磨加工技术研究进展

磁力研磨加工是提高小孔内表面质量的一种重要光整技术，利用该技术能高效提升小孔类零部件在极端环境下的使役性能。针对小孔内表面的磁力研磨光整加工，按其发展历程对磁力研磨加工技术进行总结，归纳了磁性磨粒研磨、磁针磁力研磨、液体磁性磨具研磨、超声辅助磁力研磨和电解磁力复合研磨等加工方法的技术特点，并分析评述了其局限性。对磁力研磨加工过程中材料去除机理进行了研究，材料主要以微量切削与挤压、塑性变形磨损、腐蚀磨损、电化学磨损等方式去除，材料种类不同，去除机理也不同。其中，硬脆性材料主要以脆性断裂、塑性变形和粉末化的形式去除;塑性材料在经历滑擦阶段、耕犁阶段和材料去除阶段后主要以切屑的形式去除。此外，还对磁力研磨加工过程中的材料去除模型进行了研究，对单颗磁性磨粒材料去除模型和“磁力刷”材料去除模型进行了分析讨论。最后，对磁力研磨加工技术今后的研究发展给出了建议并进行了展望。

Advances in Magnetic Abrasive Machining Technique for the Inner Surface of the Small Holes

Inner surface finishing of the small holes has become an enormous technical problem in the field of advanced manufacturing. Magnetic abrasive machining (MAM) as an important finishing technique can improve the surface quality of the small holes due to its significant advantages of flexible contact, good adaptability, and no temperature compensation. In this work, the basic principle, material removal mechanism, and material removal model of MAM are summarized. MAM can be divided into traditional magnetic abrasive machining techniques and composite magnetic abrasive machining techniques according to the development process. Traditional magnetic abrasive machining techniques mainly include magnetic abrasive grinding (MAG) technique, magnetic needle abrasive grinding (MNAG) technique, and fluid magnetic abrasive (FMA) technique. Composite magnetic grinding techniques include ultrasonic-assisted magnetic grinding (UAMG) technique and electrolytic magnetic composite grinding (EMCG) technique. MAG is the most basic technique for finishing the inner surface of the small holes. It uses the interaction between the magnetic field and magnetic abrasive particles to achieve the finishing of the workpiece surface. Due to the different positions of magnetic poles, MAG has two forms of external magnetic pole grinding (EMPG) and built-in magnetic pole grinding (BMPG). In the process of MAG, processing efficiency can be improved by increasing the grinding pressure. MNAG drives the magnetic needle to collide, scratch, and roll to remove the edges, burrs, and recast layers on the inner surface of the small holes. However, due to the effect of the magnetic needle shape, there will be a processing blind area. FMA is a novel type of precision finishing technique based on the theory of magnetic phase transition. Under the action of the magnetic field, the liquid abrasive composed of magnetic particles and abrasive particles changes from free-flowing Newtonian liquid to consolidated Bingham body. As the liquid abrasive contacts with the workpiece and generates relative motion, the finishing of the workpiece surface is realized. UAMG has high processing efficiency, but it has the limitation of being impossible to predict the motion trajectory and grinding path of abrasive particles. EMCG has the advantage of not being limited by the hardness of the material, low abrasive wear, high controllability, and high machining efficiency. However, it is only used for conductive materials. When MAM is used to finish the inner surface of the small holes, the material types are different, so the removal mechanism is also different. The removal mechanism of hard and brittle materials can be divided into brittle fracture removal, plastic deformation removal, and powdered removal. The removal mechanism of plastic materials can be divided into three stages:sliding friction stage, ploughing stage, and material removal stage. The material removal model in MAM can be divided into single magnetic abrasive material removal model and ''magnetic brush'' material removal model. However, these models have certain limitations. A perfect material removal model should be further constructed and the mechanism of MAM should be further studied. Finally, suggestions and prospects for future research and development of MAM are given.