One of the most challenging problems in the field of machining is to determine the onset of shear localization. The consequences of the emergence of shear localized chips are fluctuations in the machining forces, tool wear, deterioration of the surface quality and out-of-tolerance machined components. Several constitutive material models are developed for the simulation of shear localization during machining, especially for Ti6Al4V. However, the accuracy and capability of the proposed models for the prediction of shear localization onset have not been investigated yet. In this study, the effect of different constitutive material models in the prediction of shear localization onset has been investigated. Different material models are studied including the Johnson-Cook (J-C) material model with Cockcroft-Latham damage model, J-C material model with a J-C damage model, models based on modified J-C material models (MJ-C) with strain softening terms, and material model with power-law type strain hardening and strain rate sensitivity, with polynomial thermal softening and polynomial temperature-dependent damage. The results of the finite element models are verified using orthogonal cutting experiments in terms of chip morphology and machining forces. Metallography techniques are used along with SEM observations to elucidate the distinction between continuous and shear localized chips. The results of this study indicate that three models are capable of predicting shear localization onset. However, when compared to the experiments, where a critical cutting speed of 2.8 m/min is obtained for shear localization onset, the results revealed that the model proposed by Sima and Ozel (2016) which is a model based on MJ-C model with temperature-dependent overarching modifier and temperature-dependent material model parameters is more accurate for the prediction of shear localization onset during machining Ti6Al4V. This model is shown to reveal a good prediction for the machining forces as well.

在机械加工领域最具挑战性的问题之一是确定剪切局部化的开始。局部剪切切屑的出现会导致加工力波动，刀具磨损，表面质量下降以及加工零件的公差超出公差。开发了几种本构材料模型来模拟加工过程中的剪切局部化，特别是对于Ti6Al4V。但是，尚未对所提出的模型预测剪切局部化开始的准确性和能力进行研究。在这项研究中，研究了不同本构材料模型对剪切定位开始的影响。研究了各种材料模型，包括Johnson-Cook（JC）材料模型和Cockcroft-Latham损伤模型，具有JC损伤模型的JC材料模型，基于具有应变软化项的改进JC材料模型（MJ-C）的模型以及具有多项式热软化和多项式温度相关性的具有幂律型应变硬化和应变率敏感性的材料模型损伤。有限元模型的结果通过正交切削实验在切屑形态和加工力方面得到了验证。金相学技术与SEM观察一起使用，以阐明连续和剪切局部切屑之间的区别。这项研究的结果表明，三个模型能够预测剪切定位的开始。但是，与实验相比，对于剪切定位开始而言，临界切削速度为2.8 m / min，结果表明，由Sima和Ozel（2016）提出的模型是基于MJ-C模型的模型，该模型具有温度依赖的总体修正量和温度依赖的材料模型参数，对于预测Ti6Al4V加工过程中的剪切局部化开始更为准确。该模型也显示出对加工力的良好预测。