仿生石墨烯/陶瓷复合材料磨削去除机理与塑性域加工方法研究

Compared with traditional structural ceramics, bionic graphene/ceramic composite having higher impact toughness and flexural strength is an important new material for defense equipments. Grinding is the dominant processing method for such materials with high hardness and toughness. However, the mechanism of graphene and layered bionic structure as a toughening phase on material removal is unclear, which leads to the problems such as low grinding efficiency and poor surface integrity. This project intends to firstly establish a cross-scale simulation model conforming the real structural characteristics of the composite based on the bridge domain theory of molecular dynamics. Furthermore, the grinding removal mechanism and the mechanism of subsurface damage and the chip formation mechanism are explored through simulation and single-particle grinding experiments. Then the relationship between grinding parameters and grinding surface/subsurface quality is revealed through the grinding experiments and the indentation fracture mechanics theory on different structural directions of material. And the critical condition of plastic-domain grinding are explored. The optimized grinding scheme and the control measures for grinding surface/subsurface damage are given. Finally, the influence of special structure of composite material on the abrasion mechanism of grinding wheel is analyzed. And the influence of wear of grinding wheel on the removal form of material is analyzed, the control measures to reduce the wear of grinding wheel are given. The results of this project will provide theoretical basis for high quality, high efficiency grinding and wide application of bionic graphene/ceramic parts.

与传统结构陶瓷相比，仿生石墨烯/陶瓷材料具有更高的抗冲击韧性和抗弯强度，是重要的国防装备新材料。磨削是此类高硬度、强韧性难加工材料的主导加工方法。而作为增韧相存在的石墨烯及层状仿生结构对材料去除的作用机制不明晰，导致磨削效率低下、磨削表面完整性差等问题亟待解决。本项目拟首先基于分子动力学的桥域理论建立符合材料结构特征的跨尺度模型，进而通过数值模拟与单磨粒磨削实验揭示石墨烯增韧相及层状仿生结构对材料去除机理、亚表面损伤机理及成屑机理作用机制；然后，基于压痕断裂力学理论和磨削实验揭示材料不同结构方向上的塑性域磨削临界条件、工艺参数与表面/亚表面质量的关系，给出优化工艺方案和表面/亚表面损伤控制措施；最后，分析复合材料特殊结构对砂轮磨损机理的影响，探索砂轮磨损对材料去除形式的影响，给出减小砂轮磨损的控制措施。本项目研究成果将为仿生石墨烯/陶瓷零件的高质量、高效率加工及广泛应用提供理论基础。

本项目针对仿生石墨烯/陶瓷复合材料磨削去除机理不清、磨削表面完整性差等问题，开展了仿生石墨烯/陶瓷复合材料磨削机理和加工工艺理论基础研究。基于SPH法建立了单颗金刚石磨粒压入SiC陶瓷和仿生石墨烯/陶瓷的仿真模型，研究了压入速度和压入深度对SiC陶瓷和仿生石墨烯/陶瓷磨削过程中横向裂纹和中位裂纹扩展过程的影响，并分析了层状石墨烯增韧相排列角度对仿生石墨烯/陶瓷磨削过程中裂纹扩展的影响机制；通过单颗金刚石磨粒刻划试验，分析了仿生石墨烯/陶瓷材料的去除机理、石墨烯对单磨粒刻划过程中裂纹扩展的影响和脆-塑转变临界条件，并验证了仿真结果的准确性；通过单因素磨削试验分析了仿生石墨烯/陶瓷在不同加工参数下的表面去除机理，研究了磨削工艺参数（磨削速度、进给速度和磨削深度）对材料去除机理的影响；建立了考虑砂轮表面磨粒出刃高度服从瑞利分布的表面粗糙度理论预测模型，并引入了多磨粒重叠对粗糙度的影响；通过单因素试验分析了磨削工艺参数对表面粗糙度（Sa和Sz）、磨削表面凹坑数量和深度的影响规律；基于带有圆弧刃角的圆锥状磨粒和突出高度服从瑞利分布的假设，建立了单颗磨粒最大未变形磨削厚度、法向和切向磨削力理论模型；并从仿生石墨烯/陶瓷复合材料临界切削深度入手，分析了临界切削深度与单颗磨粒最大未变形切屑厚度之间的关系对材料去除模式的影响，建立了塑性去除和脆性去除下的二维超声辅助磨削力理论模型；通过单因素试验分析了磨削工艺参数对仿生石墨烯/陶瓷磨削过程法向磨削力和切向磨削力的影响规律；最后分析了砂轮磨损机理并通过仿真和实验研究了磨粒磨损对材料去除过程、裂纹扩展过程和磨削表面质量的影响，给出了减小砂轮磨损的工艺措施。研究成果可为仿生石墨烯/陶瓷复合材料零件的高效、低损伤加工提供重要的理论依据和技术支持。