| Sintered Nd-Fe-B is the third generation permanent magnetic material, and it has the most excellent magnetic properties in the existing permanent magnetic materials. It is hard to ensure the require shape and dimension precision of workpiece in the predicting process of sintered Nd-Fe-B magnet, so it should be shape machined after sintering. At present, the common machining methods for this material is grinding or WEDM. Sintered Nd-Fe-B magnet is a kind of typical difficult-to-machine material with high rigidity and brittleness, and the satisfying machining efficiency and machined surface quality cannot be obtained using the above processes. The compound machining method of Ultrasonic vibration-Electric discharge-Grinding (UEG) is put forward in this research work, and experiments were conducted based on the mechanics performance of sintered Nd-Fe-B to seek for the influence of ultrasonic vibration and electric discharge on the grinding process.Bending strength and fracture toughness of sintered Nd-Fe-B magnet were studied through experiments, and the results indicated there was none evidence of plastic deformation before the magnet fracture. Like the rupture of ceramic material, the fracture section was all brittleness rupture along crystal boundary. The critical dimension of native defect in sintered Nd-Fe-B magnet was calculated under the Palmqvist impressing load mode in fracture mechanics. The reason why the calculation result was higher than the grain dimension was given using the damage mechanics theory. According to the theory, sintered Nd-Fe-B magnet would momentarily rupture in the collective damage mode when the equivalent crack dimensions arrived at the critical value.The electric discharge profile machining experiment of sintered Nd-Fe-B magnet... |
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