基于时序分析与损伤力学的高速断续切削刀具时变损伤机理研究

Due to the harsh cutting conditions, the cutting tools tend to wear rapidly in high/ultra-high speed intermittent cutting of difficult to machine materials. Researches on tool failure mechanisms are crucial for proper utilization of cutting tools and acquisition of relatively long tool life. However, most of the previous researches were conducted without consideration of both the time variation of external loads and the damage within the tool material. In the present project, research on time-dependent damage mechanisms of cutting tools based on time series analysis and damage mechanics is proposed for high/ultra-high speed intermittent cutting of typical difficult to machine materials. Thermo-mechanical coupling models will be constructed for different stages of tool life cycle. Time series analysis methods will be applied to evaluate the time-domain and frequency-domain characteristics of quantities such as tool stress and specific cutting energy. The variation mechanisms of thermo-mechanical coupling behavior in cutting time will be identified based on the analysis results. A damage model linking microstructure parameters and macroscopic physical properties will be built for the cutting tools on the basis of micromechanics and continuum damage mechanics. The initial and critical damage values of the tool material will be distinguished based on the damage model. Mechanisms of tool damage evolution from microscale to macroscale will be elaborated according to the analysis results. The time-varying thermo-mechanical coupling behavior and the tool damage evolution from microscale to macroscale will be integrated using the concept of damage equivalent stress. The time-dependent damage mechanisms of cutting tools will be revealed based on the analysis of damage equivalent stress. For the purpose of enhancing tool life, an optimization method of cutting parameters will be proposed according to the time-dependent damage mechanisms of cutting tools. This project is of great significance for the development of high/ultra-high speed cutting theory and rational use of cutting tools.

在高速/超高速断续切削难加工材料条件下，恶劣的切削环境易致刀具失效。刀具失效机理研究对于合理利用刀具、获取较高刀具寿命十分重要。以往研究多未同时考虑作用于刀具的热、机械载荷的时变规律以及刀具内部损伤状态。本项目针对典型难加工材料，提出基于时序分析与损伤力学的高速断续切削刀具时变损伤机理研究。构建刀具寿命周期不同阶段的热－力耦合强场模型，采用时序分析方法确定刀具应力、切削比能等特征量的时域、频域特性，明确热－力耦合强场的时变规律；基于微观力学和连续介质损伤力学，建立关联刀具微观结构参数与宏观物理力学性能参数的损伤模型，确定损伤初始值、阈值，阐明刀具微－宏观破坏演变机制；引入损伤当量应力概念，将时变热－力耦合强场与刀具微－宏观破坏演变相结合，揭示刀具时变损伤机理；以刀具时变损伤机理为切入点，提出以高刀具寿命为目标的切削参数优化方法。本研究对深化高速/超高速切削理论、合理应用刀具有重要意义。

在高速/超高速断续切削难加工材料条件下，恶劣的切削环境导致刀具易失效。为合理利用刀具，获取较高刀具寿命，应对刀具失效机理有深刻理解。本项目基于时序分析方法与损伤力学理论，针对高速断续切削难加工材料条件下的刀具时变损伤机理进行了研究。1. 考虑锯齿状切屑的成形，提出了断续车削条件下刀具温度预测的理论方法，揭示了切削参数对刀具温度的影响。2. 针对高速断续切削条件，研究了切屑成形特点并对刀具损伤当量应力进行分析。分析结果表明，刀具损伤当量应力与切屑成形过程间具有很强的相互关系。3. 对连续以及断续硬车削条件下的陶瓷刀具的可靠性进行了研究。当断续车削条件下的空切比相对较小时，刀具性能指标的形状参数可用于刀具可靠性的计算。4. 为改善陶瓷切削刀具在断续硬车削条件下的寿命，对刀具几何参数的优化进行了研究。5. 为提高高速铣削淬硬条件下的硬质合金刀具寿命，考虑刀具材料初始微观结构，对切削参数的优化进行了研究。6. 进行了理论以及实验分析，以揭示刀具前角和切削速度对连续和断续车削淬硬钢条件下的陶瓷刀具失效机理的影响。7. 对切削比能、损伤当量应力以及加工表面粗糙度进行了研究，以确定断续硬切削条件下的最优切削参数。当进给量在0.2到0.25mm/r范围内，且切削速度在110到125m/min的范围内时，可以同时获取相对较低的能量消耗、相对较高的刀具寿命以及相对较好的加工表面质量。8. 研究了材料微观结构以及表面微观几何对氧化铝基复合陶瓷刀具断续切削性能的综合影响。本研究对深化高速/超高速切削理论、合理应用刀具有重要意义。在该项目的支持下，项目负责人以第一作者发表SCI期刊论文12篇，授权发明专利1项，申请发明专利2项，培养硕士研究生2名。