Tool path selection for high-speed ball-end milling process of hardened AISI D2 steel based on fatigue resistance
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ORIGINAL ARTICLE
Tool path selection for high-speed ball-end milling process of hardened AISI D2 steel based on fatigue resistance Weimin Huang 1 & Peirong Zhang 2 & Tong Yang 1 & Jun Zhao 3 & Chunjian Su 1 Received: 20 April 2020 / Accepted: 28 August 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract This paper aims at revealing how tool paths influence the fatigue resistance of high-speed ball-end hard milled surfaces and proposing corresponding tool path selection methods. Three kinds of tool paths (tool paths A, B, and C with angles relative to the length direction of cuboid workpiece 0°, 90°, and 45°, respectively) were utilized during high-speed milling process of hardened AISI D2 steel. The fatigue resistance of samples for different tool paths was evaluated through three-point bending fatigue tests. Results shows that tool paths have significant effect on fatigue resistance, and the maximum discrepancy in fatigue life can reach about 37.6% for different tool paths. Samples for tool path C shows the longest fatigue life when radial depth of cut ae = 0.1 mm. However, with the further increase of ae, samples for tool path A have the best fatigue resistance, followed by tool path C and B. Microscopic stress concentration and effective residual stress are the main ways by which tool paths influence the fatigue resistance. Changing tool paths leads to the difference in surface topography orientation and then in degree of microscopic stress concentration. Moreover, the effective residual stress (residual stress component in direction parallel to cyclic tensile stress) is also directly determined by tool paths. Tool path selection methods are put forward based on the aforementioned influence mechanisms. This study indicates that improving the fatigue resistance of high-speed ball-end hard milled surfaces suffering given cyclic tensile stress is feasible by choosing appropriate tool paths. Keywords High-speed hard milling . Tool path . Fatigue resistance . Microscopic stress concentration . Effective residual stress
1 Introduction Cold working steel AISI D2 is widely used to manufacture cold forming dies in virtue of high strength, high toughness, and excellent wear resistance. However, these advantages make hardened AISI D2 steel a typical difficult-to-machine material. In the
* Tong Yang [email protected] * Jun Zhao [email protected] 1
College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Qingdao 266590, People’s Republic Of China
2
School of Mechanical and Automotive Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, People’s Republic Of China
3
Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE, School of Mechanical Engineering, Shandong University, Jinan 250061, People’s Republic Of China
traditional die manufacturing process, AISI D2 steel is usually high-speed ball-end milled in annealed state. This makes subsequent heat treatment, electrical discharge machining (
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