切削过程中剪切区微观组织演化的预测模型

Prediction Model of Microstructure Evolution in Shear Zone During Cutting Process

金属切削过程中强烈的热力载荷会引起切屑内微观组织的变化。为了反映材料微观组织对剪切区力学行为的影响,提出了一种基于位错密度的剪切区微观组织演化解析模型,对切屑形成过程中塑性变形引起的微观组织演化过程进行了建模。首先,使用非等距剪切区解析模型计算出剪切区应变和应变率的分布;然后,用基于位错密度的材料模型替换Johnson-Cook流动应力模型,迭代计算剪切区温度场;最后,模拟出直角切削无氧铜、铝合金的剪切区位错密度和晶粒尺寸的演化过程。结果表明,结合位错密度建立的剪切区微观演化解析模型可较好地反映切削过程中变形场和微观组织演化的基本特征,在不同切削参数下的切削力和切屑内晶粒尺寸预测值与实验数据具有较好的一致性。

During the metal cutting process,the intense thermo-mechanical load can cause changes in the microstructure of the chips.In order to reflect the influence of the material microstructure on the mechanical behavior of shear zone,an analytical model of microstructure evolution in shear zone based on dislocation density was proposed.And it was used to model the microstructure evolution process caused by plastic deformation during chip formation.Firstly,the distribution of strain and strain rate in shear zone was calculated through the analytical model of unequal shear zone.Secondly,the Johnson-Cook(J-C)flow stress model was replaced by the material model based on dislocation density to calculate the temperature field in the shear zone iteratively.Finally,the evolution process of dislocation density and grain size in shear zone of orthogonal cutting oxygen-free copper and aluminum alloy was simulated.The results show that the analytic model for the micro-evolution of the shear zone combined with the dislocation density can better reflect the basic characteristics of the deformation field and microstructure evolution during the cutting process.The predicted values of cutting force and grain size in chips under different cutting parameters are in good agreement with the experimental data.