The deformation states within the primary shear zone (PSZ) significantly affect material removal during machining. Uncut chip thickness (UCT) is an important factor that influences the material deformation states. However, the specific mechanism by which UCT influences the deformation states within PSZ remains unknown. This study aims to investigate the relationship between the deformation states in PSZ and UCTs via in-situ measurement and microscopic characterization techniques. Using the digital image correlation (DIC) technique, strain and strain rate distributions were derived to reveal the discrepant deformation in PSZ with increasing UCT. Furthermore, velocity vector fields and Electron Back-Scattered Diffraction (EBSD) characterizations were employed to examine the heterogeneity of deformation modes. To determine the specific deformation information, a deformation extraction framework based on the deformation gradient tensor theory was developed. Thus, strong and weak shear modes within PSZ were revealed based on the full-field deformation information of compression and extension. As the UCT increased, the transition of deformation states from a strong shear state to a hybrid shear state was determined. This work presents a new understanding of the deformation mechanism within PSZ in a ductile material of pure iron. A critical UCT was proposed to guide the cutting process to avoid inefficient weak shear mode.

中文翻译：

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金属切削过程中，未切屑厚度如何影响主剪切区内的变形状态？

主剪切区 (PSZ) 内的变形状态显着影响加工过程中的材料去除。未切屑厚度（UCT）是影响材料变形状态的重要因素。然而，UCT影响PSZ内变形状态的具体机制仍不清楚。本研究旨在通过原位测量和微观表征技术研究 PSZ 和 UCT 变形状态之间的关系。使用数字图像相关 (DIC) 技术，导出应变和应变率分布，以揭示 PSZ 随 UCT 增加而出现的差异变形。此外，采用速度矢量场和电子背散射衍射（EBSD）表征来检查变形模式的异质性。为了确定具体的变形信息，开发了基于变形梯度张量理论的变形提取框架。因此，基于压缩和拉伸的全场变形信息揭示了 PSZ 内的强剪切模式和弱剪切模式。随着 UCT 的增加，变形状态从强剪切状态到混合剪切状态的转变被确定。这项工作提出了对纯铁延性材料 PSZ 内变形机制的新认识。提出了关键 UCT 来指导切割过程，以避免低效的弱剪切模式。