直角切削6061-T6铝合金剪切区力学行为及微观结构演化预测

力学行为是塑性变形微观过程的宏观表现，早期的金属切削理论模型没有考虑微观结构对切削力的影响。在考虑热力耦合效应的基础上建立了基于位错密度材料模型的6061-T6铝合金直角切削力预测模型，分析了不同切削参数下基于位错运动的塑性变形机制对切削力的影响。结合等分剪切区和非等分剪切区模型，构建了第一变形区多物理场计算方法，提出一种切屑形成过程中由塑性变形引起的微观结构演化解析模型。通过测量切削力和切屑内晶粒尺寸对模型的可行性进行了初步验证。结果表明：剪切区长度变长引起参与位错滑移的材料增多是切削深度增大导致切削力增大的主要原因。增大切削速度导致切削力的降低不是单一变量影响的结果，而是应变降低引起位错增殖数量减少和温度升高引起位错湮灭作用增加的共同作用结果。非等分剪切区模型正确反映了第一变形区温度和应力的分布特征，且与二维有限元模型分布相一致，建立的第一变形区微观结构演化解析模型能够预测切屑内位错密度和晶粒尺寸。

Prediction of mechanical behavior and microstructure evolution of shear zone in orthogonal cutting 6061-T6 aluminum alloy

Mechanical behavior is the macroscopic expression of the microscopic process of plastic deformation. Early metal cutting theoretical models did not consider the effect of microstructure on the cutting force. Based on the dislocation density material model, a 6061-T6 aluminum alloy orthogonal cutting force prediction model is established, and the influence of dislocation motion based plastic deformation mechanism on the cutting force with different cutting parameters is analyzed. By combining the model of equal division shear zones and unequal division shear zones, we construct a multi-physics field calculation method for the first deformation zone, and propose an analytical model of microstructure evolution caused by plastic deformation during chip formation. The feasibility of the model is preliminarily verified by measuring the cutting force and the size of grain in the chip. The results show that the material increase involved in the dislocation slip caused by the length of the shear zone is the main reason for the increase of the feed rate, which further leads to the increase of the cutting force. The decrease in the cutting force caused by the increasing cutting speed is not the result of a single variable, but the joint effect of the number reduction of dislocations induced by the strain reduction and the annihilation increase resulted from temperature increase. The non-divided shear zone model correctly reflects the temperature and stress distribution characteristics of the first deformation zone, and is consistent with the two-dimensional finite element model. The analytical model of the microstructure evolution of the first deformation zone can predict the dislocation density and grain size in the chip.