基于流-固耦合力学原理的金属切削机理研究

本项目针对金属和合金材料高速切削过程的材料失稳行为和去除机理开展研究。通过材料高温高应变率动态力学性能实验研究获得材料热粘塑性本构模型。通过材料正交切削模拟实验测定不同切削速度下切削力和工件温度的变化规律。获得连续切屑、锯齿切屑和碎屑的实验样品,通过扫描电镜微观观察对切屑形成的微结构演化机制进行定性分析，确定不同切削条件对切屑形成机制和微结构特征的影响规律。理论上开展一般加载条件下材料塑性失稳行为的分析，建立判断不同形貌切屑材料失稳行为的判据。应用流-固耦合力学原理描述材料切削过程。基于这两方面的分析和考虑提出描述材料正交切削过程的流-固耦合动力学模型。重点研究切屑材料塑性流动过程中的失稳行为和能量耗散机制。考察非线性效应、惯性和尺度效应、应变梯度以及热和质量对流现象对切屑形成机制产生的影响。研究方法采用以实验观察、理论分析和数值模拟相结合的综合方法。

This project involves the studies of plastic instability behaviors and the removed mechanisms of chip materials from workpiece surface of mild steel and Ni or Ti alloys in high speed machaining process. In the experiments of material under the loading conditions with high temperature and high strain rate, dynamic mechanical properties of the material are measured to obtain the thermo-viscoplastic constitutive equation. In the experimental studies modeling the orthogonal cutting process, the transient temperature fields and the cutting forces of tool applying on workpiece materials are measured. By the mircoscopic experimental observations, the microstructural changes of chip materials are determined qualitatively and the influence of cutting processing conditions on the microstructures of chips are studied. Following the modeling experimental observations, the theoretical analysis and numerical investigation on the high speed cutting process and removed mechnisms of chip materials are carried out. By employing the analytic results on the material plastic instability behaviors and describing the cutting process of material by the coupling fluid-solid mechanical principle, a new analytical model is proposed for studying the physical essences of the orthogonal cutting process and the removed mechanisms of chip material.This model focuses on the consideration of the mechnisms of chip separation from the workpiece surface and the energy dissipation in wrokpiece material. Furthermore, it considers the nonlinear effect, ineraia and size effects, strain gradient and the convection of heat and mass as well as microstructural changes on the cutting process.In this study, the advanced experimental measuring and observing technologies, theoretical analysis methods and numerical simulation means are used.