高速切削Ti-6Al-4V绝热剪切带应变、应变率有限元模拟研究

Strain and strain rate analyses of adiabatic shear band with finite element simulation for Ti-6Al-4V high speed machining

塑性金属材料高速切削过程中存在绝热剪切行为,绝热剪切带内的应变、应变率分布规律是研究高速切削绝热剪切带特性的基础。首先,应用有限元软件ABAQUS/Explicit建立Ti-6Al-4V热-位移耦合平面应变二维切削模型,工件材料采用Johnson-Cook（J-C）本构模型,基于J-C失效判据设置切屑和工件分离准则,实现对Ti-6Al-4V的切削过程仿真。其次,对比分析有限元仿真与切削实验获取的切屑形貌,验证有限元模型的准确性。最后,分析Ti-6Al-4V高速切削绝热剪切带处应变、应变率变化规律。结果表明：切削速度在180-3000m/min范围内,随切削速度提高,切屑绝热剪切带内的应变、应变率先增大后趋于稳定,绝热剪切带变形程度增加直至韧性断裂。研究结果有助于准确预测绝热剪切带的断裂并揭示其演化机制,通过利用材料的绝热剪切行为,可控制高速切削过程中的切屑形态,改善Ti-6Al-4V的切削加工性。

Adiabatic shear behavior widely exists in high speed machining process of plastic metal material. The distributions of strain and strain rate in adiabatic shear band are foundamental for the research of the property of adiabatic shear band in high speed machining. Numerical 2D plane-strain coupled temperature-displacement simulation model for high speed machining of Ti- 6Al-4V is firstly presented with finite element software ABAQUS/Explicit. The workpiece material deformation behaviour is de- scribed by Johnson-Cook（J-C） model. The chip-workpiece separation criterion is set up with J-C damage law. The finite element model is then verified by comparing the chip morphology obtained by simulation with experimental results. The distributions of strain and strain rate in adiabatic shear band are lastly analysed. The results show that within the simulation cutting speed ranged from 180m/min to 3 000m/min,both strain and strain rate in adiabatic shear band increase initially and then tends to be stable. The deformation degree in adiabatic shear band increases with increasing the cutting speed till the deformed material seperates with ductile fracture. The research results can be helpful for the accurate prediction of the materials fracture deformation in adiabatic shear band and understand of deformation evolutionary mechanism. Appropriate chip shape may be obtained and the machinability of titanium alloy is improved with the research of material adiabatic shear property in high speed machining process.