高速正交切削SiC_p/Al复合材料的切屑形成及边界损伤仿真研究

Simulation Study of Chip Forming and Boundary Damage on High Speed Orthogonal Cutting SiC_p/Al Composites

针对SiCp/Al复合材料颗粒增强相与基体相不同的机械力学性能,对照SiCp/Al复合材料金相照片中的SiC颗粒形状与分布状态建立仿真模型,并对SiCp/Al复合材料的颗粒和基体进行分别定义。使用ABAQUS有限元软件仿真研究了高速切削复合材料切屑的形成、工件已加工表面的缺陷特征、边界损伤的形成机理及切削用量对边界损伤程度的影响规律。结果表明:在第1变形区切削变形主体表现为沿剪切角方向Al合金基体的剪切滑移,滑移主要发生在SiC颗粒与Al合金基体的边界邻近区域;对刀刃直接作用的SiC颗粒,由于其压力较大,会发生破碎现象;SiCp/Al复合材料的切屑形态以单元状切屑和由几个单元构成的节状切屑为主;SiC颗粒的破碎和整体剥落是造成已加工表面缺陷的重要因素;负剪切角是产生边界损伤的标志;切削速度对边界缺损几何尺寸大小的影响较小,切削深度对边界缺损几何尺寸大小的影响较大;随着切削深度的增大,边界缺损长度呈直线上升趋势,边界缺损高度先显著增加后缓慢增加。

According to the different mechanical properties of particle reinforced phase and matrix phase,the finite element was established,which was compared with the shape and the distribution of SiC particle in the metallograph. The finite element software ABAQUS was used to define both the particles and matrix during high speed cutting SiCp/Al composites and the high speed cutting process was studied in details.The chip forming in the cutting process,the defects in the workpiece surface and the boundary damage formation mechanism were analyzed. Simultaneously,the influence of cutting parameter on the degree of boundary damage was also studied. The results indicated that the deformation in the primary deformation zone was almost the shear ship of Al matrix along the shear angle,and the shear ship was mainly found in the boundary adjacent region between SiC particles and Al matrix. Owing to the press,the SiC particleswhich were directly affected by the cutting edge were easily destroyed. Unit chips and segmental chip composed with several units chips are the main chip morphology of SiCp/Al composites. The fracture and the whole spalling of SiC particles were the important reasons that caused the defects of machined surface.The negative shear angle was the sign of boundary damage. The cutting speed has little influence on the geometry size of boundary defect; otherwise the influence of the cutting depth on the geometry size of boundary defect is large. With the increasing of cutting depth,the length of boundary damage increased in straight line. Meanwhile the height of boundary damage increased significantly at the first and then increased slowly.