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Experiment research on grind-hardening of AISI5140 steel based on thermal compensation
Xiangming Huang,Yinghui Ren,Bo Zheng,Zhaohui Deng 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.8
The grind-hardening process utilizes the heat generated to induce martensitic phase transformation. However, the maximum achievable harden layer depth is limited due to high grinding forces, and the tensile residual stress appears on the ground surface in the grindhardening process. This paper proposes a new grind-hardening technology using thermal compensation. The workpiece of AISI5140 steel is preheated by electric resistance heating, and ground under the condition of the workpiece temperature 25°C, 120°C, 180°C and 240°C. The grinding force, harden layer depth and surface quality including residual stress on ground surface, surface roughness and micro-hardness are investigated. The experimental results show that a deep harden layer with a fine grain martensite can be obtained with the thermal compensation. The ground workpiece surface produces a certain compressive residual stress, and the residual compressive stress value increases with preheating temperature. As the preheating temperature increases, grinding force slightly decreases, while there is slightly increment of surface roughness. Compared with the conventional grind-hardening process, both the harden layer depth and residual stress distribution are significantly improved.
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Qian Li,Aihong Ji,Huan Shen,Renshu Li,Kun Liu,Xiangming Zheng,Lida Shen,Qingfei Han 한국항공우주학회 2022 International Journal of Aeronautical and Space Sc Vol.23 No.2
The design of a flapping-wing aircraft is mainly inspired by flying animals: to improve the lift and efficiency of flapping-wing aircraft, their wings, an essential part of the aircraft, mimic the configuration and geometric characteristics of flying animals. Herein, we conducted wing parameter optimization experiments by changing the wing-vein layout, aspect ratio (AR), surface area, and leading-edge-rod flexibility of a flapping-wing aircraft having four wings with double wing clap-and-fling effects. The AR and leading-edge-rod flexibility significantly influenced the lift through the aircraft’s clap-and-fling effects. Analyzing the wing deformation and lift fluctuation revealed that the leading-edge-rod flexibility delayed the trailing-edge separation during clapping, resulting in a large lift at the beginning of peeling. A pentagonal wing of 155-mm wing length, 5.0 AR, a 100-mm breaking point, and an 80-mm wing-vein convergence point at the leading-edge-rod near the wing root was deemed the optimal wing design. This optimal wing design was used to build a 30 g flapping-wing aircraft for an outdoor flight test, which could fly for 6.5 min with a 4.5-g load, thus demonstrating the developed prototype’s potential for autonomous flight.
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