超声振动辅助磨削脆性材料去除机理

Brittle material removal mechanism of ultrasonic vibration assisted grinding

脆性材料塑性去除有利于提高加工表面质量。采用切向、轴向和径向超声振动辅助磨削加工方法,对烧结钕铁硼NdFeB永磁材料去除机理进行了试验研究,结合脆性材料去除脆-塑性转变临界条件,分析了不同超声振动辅助方式对材料去除机理的影响。分析得出以下结论:轴向超声振动辅助磨削加工过程中,材料主要以塑性剪切的方式去除;切向超声振动辅助磨削加工过程中,材料主要以塑性方式去除,同时伴有少量沿晶断裂;径向超声振动辅助磨削加工过程中,工件材料主要以断裂破碎的方式去除,而且加工表面残留裂纹。因而,轴向超声振动辅助磨削最有利于实现脆性材料塑性去除。

To remove the brittle material in ductile state can help to improve the machined surface quality. Experiments of material removal mechanism for NdFeB are conducted by using tangential ultrasonic vibration assisted grinding,axial ultrasonic vibration assisted grinding and normal ultrasonic vibration assisted grinding. Based on the critical condition of brittle-ductile transition,the effects of different ultrasonic vibration modes on material removal mechanism are analyzed. Results indicate that the material is mainly removed in the form of plastic shear in axial ultrasonic vibration assisted grinding. The material is mainly removed in the form of transgranular fracture,plastic shear and little intergranular fracture in tangential ultrasonic vibration assisted grinding. While in normal ultrasonic vibration assisted grinding,the material is mainly removed in the form of fracture crash and the cracks remain in the machined surface. So axial ultrasonic vibration assisted grinding is the best machining method to realize the ductile grinding on brittle materials.