The formation of burrs is among the most significant factors affecting quality and productivity in machining. Burrs are a negative byproduct of machining processes that are difficult to avoid because of a limited understanding of the complex burr formation mechanisms in relation to cutting conditions, including both process parameters and tool condition. Thus, the objective of this work was to characterize burr formation under finish machining conditions via a high-speed, high-resolution in-situ experimental method. Various parameters pertaining to burr geometry such as height, thickness, and initial negative shear angle were measured both during and after cutting. Results showed that varying the conditions of uncut chip thickness, tool-wear, and cutting speed all have a significant effect on burr formation, although certain burr metrics were found to be insensitive with respect to different process conditions because the difference was statistically insignificant. This study provides new insights into the relationships between the workpiece material's microstructure, machining parameters, and tool condition on both crack formation and propagation/plasticity during burr formation. Using digital image correlation (DIC) and a physics-based process model not previously utilized for burr formation analysis, the displacement and corresponding flow stress were calculated at the exit burr root location. This novel semi-analytical approach revealed that the normalized stress at the exit burr root was approximately equal to the flow stress for a variety of different conditions, indicating the potential for model-based prediction of burr formation mechanics. Finally, this study investigates factors that influence fracture evolution during exit burr formation. It was found that negative exit burrs are a direct result of high strain rate and high uncut chip thickness, which was expected, but also a microstructural size effect and a tool-wear effect, neither of which have been previously reported. By harnessing ultra-high-speed imaging and advanced optical microscopy techniques, this manuscript deals with the fundamentals of burr formation, including new insights into material response at the grain-scale to the loads imposed with both sharp and worn tools.

毛刺的形成是影响加工质量和生产率的最重要因素之一。毛刺是机加工过程的负面副产品，由于对与切削条件（包括工艺参数和刀具条件）相关的复杂毛刺形成机制的了解有限，因此很难避免。因此，这项工作的目的是通过高速、高分辨率的原位实验方法来表征精加工条件下的毛刺形成。在切割过程中和切割后测量了与毛刺几何形状有关的各种参数，例如高度、厚度和初始负剪切角。结果表明，改变未切削切屑厚度、刀具磨损和切削速度的条件都会对毛刺形成产生显着影响，尽管发现某些毛刺指标对不同的工艺条件不敏感，因为差异在统计上不显着。这项研究为工件材料的微观结构、加工参数和刀具条件对毛刺形成过程中裂纹形成和传播/塑性之间的关系提供了新的见解。使用数字图像相关 (DIC) 和以前未用于毛刺形成分析的基于物理的过程模型，计算出毛刺出口根部位置的位移和相应的流动应力。这种新颖的半解析方法表明，在各种不同条件下，出口毛刺根部的归一化应力大约等于流变应力，表明基于模型的毛刺形成力学预测的潜力。最后，本研究调查了影响出口毛刺形成过程中断裂演化的因素。结果发现，负出口毛刺是高应变率和高未切削切屑厚度的直接结果，这是预期的，也是微观结构尺寸效应和刀具磨损效应的直接结果，这两种情况以前都没有报道过。通过利用超高速成像和先进的光学显微镜技术，这份手稿涉及毛刺形成的基本原理，包括对材料在晶粒尺度上对锋利和磨损工具施加的载荷的响应的新见解。结果发现，负出口毛刺是高应变率和高未切削切屑厚度的直接结果，这是预期的，也是微观结构尺寸效应和刀具磨损效应的直接结果，这两种情况以前都没有报道过。通过利用超高速成像和先进的光学显微镜技术，这份手稿涉及毛刺形成的基本原理，包括对材料在晶粒尺度上对锋利和磨损工具施加的载荷的响应的新见解。结果发现，负出口毛刺是高应变率和高未切削切屑厚度的直接结果，这是预期的，也是微观结构尺寸效应和刀具磨损效应的直接结果，这两种情况以前都没有报道过。通过利用超高速成像和先进的光学显微镜技术，这份手稿涉及毛刺形成的基本原理，包括对材料在晶粒尺度上对锋利和磨损工具施加的载荷的响应的新见解。