双尺度SiCp/Al基复合材料精密切削加工机理的多尺度研究

Aluminum matrix composites are increasingly being used in the aeronautic, aerospace, electronic packaging, automotive industries, because of their improved strength, stiffness, high thermal conductivity and low coefficient of thermal expansion. Based on machining experiments and multiscale (MS) simulation technique which connects microstructure-based finite element (FE) modeling and molecular dynamics (MD) methods, hybrid multiscale and hierarchical multiscale cutting simulation models for micro- and nanosized silicon carbide particles (SiCp) reinforced aluminium-based matrix composite materials which spans micro-scale to macro-scale are established respectively. Through this simulation model, materials deformation and breakage, the cutting heat generation and pervasion, the interaction between tool and workpiece are explored. Combining to the experimental results, the influence of volume fractions and sizes of SiCp, adhesive strength, defect structures and tool geometric parameters on the chip generation, the generation and evolvement of defects and dislocations at machined surface and sub surface, residual stress and the micro-wear and macro-wear of tool is investigated. The cutting performance of aluminum-based matrix composite is exhibited by the microstructure of composite materials and the interaction mechanism between workpiece material and polycrystalline diamond cutting tool (PCD). Further, several significant machining mechanisms of this material are interpreted. All these pursuits will provide theoretical evidences for the desigh, preparation and machining of novel aluminium-based matrix composites reinforced by nano- and microsized SiCp and make this materials apply to the engineering field effectively.

本项目针对工业领域对具有优异力学性能与良好切削加工性的双尺度颗粒增强Al基复合材料的需求，采用切削加工实验和多尺度建模方法，利用多尺度仿真理论，结合复合材料微观结构模型，建立多场耦合条件下双尺度SiCp/Al基复合材料切削加工多尺度仿真模型，探索颗粒增强Al基复合材料切削过程材料变形与破坏机制、切削热产生与扩散机制；结合实验结果，研究颗粒尺度、颗粒含量、界面结合强度、缺陷结构，以及刀具几何参数对切屑形成、表面及亚表面缺陷、位错产生及扩展、残余应力、刀具宏—微观磨损等的影响规律。根据SiCp/Al基复合材料微观结构以及与金刚石刀具相互作用机制来揭示其加工特性，进一步阐释SiCp/Al基复合材料若干加工机理，掌握其加工特性。为新型双尺度Al基复合材料的优化设计、制备、加工及其在航空航天等领域的应用提供理论依据和指导。

本文主要研究内容包括切削过程高应变率条件下纳米颗粒SiCp/Al基复合材料力学性能表征、精密车削纳米尺寸SiCp/Al基复合材料的递阶多尺度仿真模型的建立和微米及纳米SiCp/Al基复合材料的不同尺度切削加工实验研究。.主要结果：基体沿着颗粒脱粘处发生韧性撕裂，在切屑的内表面形成锯齿状。刀具的摩擦作用使得颗粒从已加工表面拔出，颗粒的脱粘和拔出使得已加工表面较不平整。在精密加工纳米颗粒铝基复合材料过程中，SiC颗粒承受主要的切削抗力，SiC颗粒上的应力明显高于铝基体。由于切削过程中温度主要来源于材料的塑性变形和刀具、工件间的摩擦作用，切削温度主要集中在刀具-切屑接触区和第一剪切区。SiC颗粒分布不均匀，导致切削过程中切削力波动没有明显的规律。