基于有限元模拟的钛合金锯齿状切屑形成机理

Mechanism of saw-tooth chip formation of titanium alloy based on finite element simulation

为了研究钛合金切削加工中的锯齿状切屑形成机理,通过对材料本构模型、刀-屑接触摩擦、切屑分离和绝热剪切等关键物理环节建模,建立了切削加工有限元模型,并经试验验证了该模型的正确性.利用该有限元模型模拟了钛合金Ti6Al4V锯齿状切屑形成的全过程,通过分析一个锯齿节块的形成过程,以及该过程中的切削力同步发展变化规律和第一变形区中不同部位的三点应力、温度曲线,揭示了钛合金锯齿状切屑的形成机理是靠近切削尖处的材料发生热塑性失稳,继而在整个第一变形区诱发集中滑移,造成绝热剪切,从而形成节块状的锯齿状切屑.

To study the saw-tooth chip formation mechanism of titanium alloy during a cutting process, a finite element model was developed. Several key finite element techniques, such as the material constitutive model, contact between tool and chip, chip separation and adiabatic shearing, were implemented to improve the accuracy of the finite element simulation. Saw-tooth chip was simulated using this model, and the chip morphology and cutting force agreed well with the experimental results, which showing the finite element model is reasonable. The saw-tooth chip formation process was studied through describing the formation process of a chip segment and analyzing the variation law of cutting force. Furthermore, the stress and temperature curves of three points in the primary shear zone were analyzed. The simulation shows that the material is softened firstly ahead of tool tip because of high temperature, which induces thermoplastic instability, and then the structure of chip goes instability, which causes the shear localization and adiabatic shear bands, finally leading to the formation of saw-tooth chip.