低温石墨烯/离子液纳米流体微量润滑磨削界面换热及摩擦学机理研究

This project proposes a new cooling and lubricating technique, which is cryogenic minimum quantity lubrication with graphene/ionic liquid nanofluid, in an effort to address the bottleneck that the minimum quantity lubrication technique cannot meet the cooling requirements in conventional grinding. The new technique takes advantage of the excellent heat transfer performance of graphene nanoparticles to increase the convective heat transfer coefficient. The ionic liquid with low pour point and extremely low vapour pressure is utilized to break through the restrictions on the heat transfer capacity, which are caused by the high pour point and film boiling of grinding fluids. The graphene nanoparticles possess extremely thin thickness, lamellar structure with low shear strength, and superhigh mechanical strength. The excellent properties above make graphene nanoparticles easier to enter into the grinding interface and to form lubricating film. Through studying the nanofluid properties, to synthesize the nanofluid with the optimal performance considering the thermo-physical and tribological properties. Through investigating the fluid field in the grinding zone, to reveal the influence mechanism of processing parameters on the wetted area, and to provide the optimal matching of the processing parameters. On this basis, through studying the heat transfer mechanism of the cryogenic aerosol jet on the grinding interface, to establish the quantitative relation between the convective heat transfer coefficient and spray parameters. Through researching the formation mechanism of the lubricating film on the grinding interface, to reveal the tribological mechanism of the graphene/ionic liquid nanofluid to reduce friction and to resist wear. Through carrying out grinding experiments for difficult-to-cut materials based on the new technique, to establish the grinding theory of cryogenic minimum quantity lubrication with graphene/ionic liquid nanofluid. This new technique will furthest promote the heat transfer ability of the minimum quantity lubrication technique, and will be hopeful to replace the traditional flood cooling and lubricating technique in conventional grinding. Therefore, this research has great theoretical significance, broad application prospect and practical economic value.

针对普通磨削加工中微量润滑换热能力不足的瓶颈，提出一种新方法—低温石墨烯/离子液纳米流体微量润滑。利用石墨烯的突出传热性能增加对流换热系数，利用离子液的低倾点与极低蒸汽压，突破磨削液的高倾点及成膜沸腾对换热能力的限制。石墨烯的极薄厚度、低剪切强度层状结构和超高机械强度，更易进入磨削界面润滑成膜。通过纳米流体性能研究，综合考虑热物性与摩擦学性能，制备最优纳米流体。研究磨削区流场，揭示工艺参数对浸润面积的影响机制，给出最优匹配。在此基础上，研究低温气雾射流在磨削界面换热机理，建立对流换热系数与雾化参数的定量关系；研究石墨烯/离子液纳米流体在磨削界面润滑成膜机理，揭示减摩抗磨的摩擦学机理；开展基于该方法的难加工材料磨削实验，建立低温石墨烯/离子液纳米流体微量润滑磨削加工理论。该方法最大限度地提升了微量润滑的换热能力，有望取代浇注式冷却润滑的地位，因此具有重大理论意义、广阔应用前景和实际经济价值。

针对普通磨削加工中微量润滑技术换热能力不足的瓶颈，本项目提出一种新的冷却润滑方法——低温石墨烯/离子液纳米流体微量润滑。利用石墨烯的突出传热性能增加对流换热系数，利用离子液的低倾点与极低蒸汽压，突破磨削液的高倾点及成膜沸腾对换热能力的限制。石墨烯具有极薄的厚度、低剪切强度的层状结构和超高的机械强度，使其更易进入磨削界面润滑成膜。本项目围绕低温石墨烯/离子液纳米流体微量润滑磨削界面的换热及摩擦学机理，开展了系统的理论分析、仿真模拟和实验研究。.1）建立了石墨烯/离子液纳米流体的双步制备方法，给出了最优的纳米流体制备工艺参数。研究了石墨烯/离子液纳米流体的热物性，揭示了石墨烯纳米片的质量分数、层数和横向尺寸对热物性的影响规律。.2）设计了低温微量冷却润滑系统，搭建了低温石墨烯/离子液纳米流体微量润滑磨削加工实验平台。研究了低温石墨烯/离子液纳米流体微量润滑磨削加工区域的流场，揭示了供液参数、喷嘴的布置以及磨削工艺参数对磨削区雾滴浸润面积的影响机制。.3）建立了磨削区已加工表面热源分布形状的计算方法，提出了直角三角形和抛物线两种已加工表面热源分布形状，并以已加工表面最大无量纲温度的误差小于15%作为工程许可的误差范围，给出了直角三角形热源和抛物线热源适用的磨削工艺参数范围。.4）研究了低温石墨烯/离子液纳米流体微量润滑磨削界面的换热机理，以及减摩抗磨的摩擦学机理，揭示了磨削界面热量的产生与传散机制，阐明了纳米流体改善微量润滑磨削界面润滑特性的摩擦学机理。.5）开展了基于低温石墨烯/离子液纳米流体微量润滑的镍基合金磨削加工实验研究，以磨削力、磨削力比、表面粗糙度、磨削温度和热量分配比为评价指标，证明了低温石墨烯/离子液纳米流体微量润滑技术具有良好的冷却润滑性能，具有取代浇注式冷却润滑的巨大潜力。.通过本项目研究，形成了低温石墨烯/离子液纳米流体微量润滑磨削加工理论与技术体系，研究成果在普通磨削加工领域具有广阔的应用前景。