Johnson-Cook(J-C)本构模型不适用于Ti-6Al-4V合金高速切削有限元模拟,因为它在重冲击和高温下没有响应的动态再结晶软化作用。在本文中,建立了考虑再结晶效应的改进本构模型,并将参数与分离式霍普金森压杆(SHPB)试验的流动应力应变数据进行拟合。研究了切削有限元模拟的相关理论,如非线性本构弹塑性变形,应变状态,和材料产量。包括Recht剪切破坏不稳定性准则和改进模型的子程序在Fortran中编码并嵌入有限元仿真软件AdvantEdgeFEM中,以及返回映射应力积分算法。当温度从950°C升高到1000°C时,改进模型的模拟应力从460MPa急剧下降到220MPa,下降了46.7%,而J-C模型仅下降了10%。对比研究表明,改进本构模拟的应力变化比J-C本构模拟更接近SHPB试验结果,当表示高速铣削中的高温和大冲击时,新的更合适。
The Johnson-Cook (J-C) constitutive model is not suitable for Ti-6Al-4V alloy in the high-speed cutting finite element simulation, as it has no response dynamic recrystallization softening effect under heavy impact and high temperature. In this paper, an improved constitutive model considering the recrystallization effect was established, and the parameters were fitted with the data of flow stress-strain of the Split Hopkinson Pressure Bar (SHPB) test. The relevant theories of cutting finite element simulation were studied, such as nonlinear constitutive elastic-plastic deformation, strain state, and material yield. A
subroutine that included the Recht shear failure instability criterion and the improved model was coded in Fortran and embedded in the finite element simulation software AdvantEdge FEM, along with the return mapping stress integration algorithm. The simulated stress of the improved model dropped dramatically from 460 MPa to 220 MPa when the temperature rises from 950 °C to 1000 °C, and its decline reached 46.7%, while the J-C model only decreased by 10%. Comparative studies indicate that the stress change of the improved constitutive simulation is closer to the SHPB test results than the J-C constitutive, and the new one is more suitable when it expresses the high temperature and heavy impact in the high-speed milling.