干式车削不同淬硬状态高硬高强高耐磨钢的热力效应研究

This is an environment friendly, resource conservation，multidisciplinary and advanced project. In this project, experimental investigations in finish dry hard turning (FDHT) of the high hardness, strength and wear resistance steel Cr12MoV at different hardness levels are conducted with the PCBN cutting tool. The mechanical behavior, dynamic behavior in the primay deformation zone and damage mechanism within machined surface induced by the thermo-mechanical effects in dry cutting deformation zones, are investiged systematically by utilizing friction and wear and tension tests at different high temperature levels, macroscopic and microscopic analysis and finite element simulation. The problems solved in theory are as follows: (1) inflexnion hardness of sudden change of mechanical behavior and underlying mechanisms; sticking-sliding mixed friction mechanical behavior and model along chip-tool-workpiece two interfaces. (2) fracture mode and critical criterion of the material instability in the primary shear zone; microscopic model and transformation mechanism of microstructure evolution in the primary shear zone; relationship between the adiabatic shear behavior and workpiece hardness. (3) formation and expand law and mechanism of the crack within the machined surface along tool-workpece interface and rigid-elastic-viscoplastic mechanical model, control equation and boundary condition of the crack-tip field; dynamic strain behavior and microscopic models of microstructure evolution within machined surface. The study is of great significance and reference value in further developing the theory of "cutting instead of grinding" green cutting technology and accelerating generalization and application of the technology in the production.

本项目属于面向环境友好、资源节约、多学科交叉的前沿性课题。通过使用PCBN刀具对不同淬硬状态高硬高强高耐磨钢Cr12MoV的精密干式硬态车削试验，结合不同高温下的摩擦磨损与拉伸试验，采用宏观测试、微观分析及有限元仿真等方法，系统研究干式切削变形区热力效应下的力学行为、主剪切区的动态行为、已加工表面的损伤机制等内容。理论上解决：（1）力学突变行为的拐点硬度及内在机制；屑-刀-工双界面粘结-滑移混合摩擦力学行为及模型。（2）主剪切区材料失稳的断裂模式和临界判据；主剪切区变质层微观组织演变的微观模型及转变机制；工件淬硬状态与绝热剪切行为的关联机制。（3）刀-工界面已加工表面微裂纹产生、扩展的机理、规律，及裂纹尖端场的刚-弹黏塑性力学模型、控制方程和边界条件；已加工表层动态应变行为及微观组织演变的微观模型。 该研究对进一步推动"以切代磨"绿色切削技术理论的发展，促进其在生产中的应用具有重要意义。

干式硬态切削技术是20世纪80年代以来发展起来的具有高效率、低能耗、无污染、高精度、加工表面损伤小的绿色切削技术，是机械加工未来“绿色化”发展的主流方向。. 通过使用PCBN刀具对不同淬硬状态高硬高强高耐磨钢Cr12MoV的精密干式硬态车削试验，结合霍普金森压杆及摩擦磨损试验系统，采用宏观测试、微观分析及有限元仿真等方法，系统研究了干式硬态切削时变形区的热力效应问题，主要研究内容和贡献如下：. （1）探明了切削速度、走刀量、切削深度、工件硬度等参数对切削力的影响规律，揭示了工件淬硬状态对力学突变行为的作用机制；（2）构建了屑-刀-工双界面粘结-滑移混合摩擦力学行为及模型；（3）揭示了干式硬态切削不同淬硬状态淬硬钢时切屑成形机理及锯齿形切屑成形的临界条件，主变形区组织转变机制，建立了工件淬硬状态与绝热剪切行为的关联机制；（4）构建了切屑根部微裂纹产生、扩展的机理、规律，及裂纹尖端场的刚-弹黏塑性力学模型、控制方程和边界条件；（5）揭示了主剪切区材料失稳断裂的模式、热力效应、临界条件；（6）揭示了干式车削不同淬硬状态高强高硬高耐磨钢时，PCBN刀具的摩擦特性、磨损形貌及形式、磨损机理、刀具寿命；（7）探明了基于刀-工界面粘结-滑移混合摩擦条件下，刀-工界面热力效应对已加工表面（层）微观组织的影响规律及转变机制，分析了已加工表面（层）微裂纹的形成机理；. 该研究对进一步推动“以切代磨”绿色切削技术理论的发展，促进其在生产中的应用具有重要意义。