Analysis of burr formation in finish machining of nickel-based superalloy with worn tools using micro-scale in-situ techniques
Analysis of burr formation in finish machining of nickel-based superalloy with worn tools using micro-scale in-situ techniques
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DOI：
10.1016/j.ijmachtools.2023.104030
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发表时间：
2023-05
影响因子：
14
通讯作者：
H. Zannoun;J. Schoop
中科院分区：
文献类型：
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作者：
H. Zannoun;J. Schoop
毛刺的形成是影响机械加工质量和生产率的重要因素之一。毛刺是加工过程中的一种负面副产品，由于对与切割条件有关的复杂毛刺形成机理的了解有限，因此难以避免。因此，这项工作的目的是通过高速、高分辨率的现场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，如高度、厚度和初始负剪切角。结果表明，改变未加工切屑厚度、刀具磨损和切割速度都对毛刺的形成有显著影响，尽管某些毛刺指标对不同的工艺条件不敏感，因为差异在统计学上不显著。这项研究为研究毛刺形成过程中裂纹形成与扩展/塑性之间的关系提供了新的见解。利用数字图像相关(DIC)和以前未用于毛刺形成分析的物理过程模型，计算了出口毛刺根部位置的位移和相应的流动应力。这种新的半解析方法表明，在各种不同的条件下，毛刺出口根部的归一化应力与流动应力近似相等，这表明基于模型的毛刺形成机制的预测是有潜力的。最后，研究了出口毛刺形成过程中影响裂缝演化的因素。研究发现，负出口毛刺是高应变率和高未加工切屑厚度的直接结果，但也是组织尺寸效应和刀具磨损效应的结果，这两种效应以前都没有报道过。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，包括对材料在颗粒尺度上对锋利和磨损的工具施加的载荷做出反应的新见解。
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.