PBX切屑的细观特征及形成机理研究

Microstructure and Formation Mechanism of PBX Chips

采用激光粒度仪测试高聚物粘结炸药(PBX)切屑的粒径,表明相同工艺参数下加切削液的切屑平均粒径大于干车削的,同时粒径随进给量增大而增大,随机床主轴转数提高而减小,未体现出与车削深度相关的明显关系。利用SEM观测发现PBX切屑主要有针状、块状和鳞片状三种细观形态,切屑的形成体现为裂纹的成核扩展导致的宏观断裂,并主要表现为炸药颗粒的穿晶断裂。使用工业CT探测试样亚表面表明裂纹的扩展路径和刀具工件相对运动状态以及工件结构边界条件有关,方向指向较为薄弱的工件表面。建立的切屑形成过程唯象模型有助于理解切屑的形成机理。

Studying on microstructure of PBX chips and its formation mechanism is helpful to understand the forming process of machined surface. It＇s of a great significance to guarantee and improve machining surface quality. The laser particle size analyzer was employed to detect PBX chips samples. It shows that the average size of chips which prepared by turning with cutting fluid is larger than that prepared by dry turning, the size increases with feed and decreases with the elevation of machine spindle revolutions, and has no obvious relationship to turning depth. Through the observation via scanning electron microscope, we can discover that chips mainly have three types of micro-shapes like aeicular,massive and squamose,its formation corresponds to PBX macro-fracture which caused by the nucleation and growth of crack and mainly embodied as transgranular fracture of explosive particles. The detection of PBX sampler sub-surface through industrial CT suggests that the crack propagation path points to workpiece surface generally, it relates to relative movement state between cutting tool and workpiece, and relates to structural boundary conditions of workpiece too. The phenomenologieal chip formation model can help to master its formation mechanism.