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2024-T3 및 황동의 작은 표면결함재의 피로균열 성장특성에 관한 연구
서창민(Chang-Min Suh),오명석(Myung-Suck Oh) 한국해양공학회 1996 韓國海洋工學會誌 Vol.10 No.1
In this paper, rotating bending fatigue tests have been carried out to investigate the growth behaviors of surface fatigue crack initiated from a small artificial surface defect, that might exist in real structures, on 2024-T3 and 6:4 brass. The test results are analysed in the viewpoints of both strength of materials and fracture mechanics, it can be concluded as follows.<br/> The effect of a small artificial surface defect upon the fatigue strength is very large. The sensitivity of 2024-T3 on the defect is higher than that of 6:4 brass.<br/> The growth behavior of the surface fatigue crack of 2024-T3 is different from that of 6:4 brass. The growth rate of the surface fatigue crack of 2024-T3 is considerably rapid in the early stage of the fatigue life and apt to decrease in the later stage.<br/> It was impossible to establish a unifying approach in the analysis of crack growth behavior of 2024-T3 and 6:4 brass using the maximum stress intensity factor because of their dependence on stress level. But if the elastic strain and cyclic total strain intensity factor range were applied to obtain the growth rate of surface fatigue cracks of the materials, the data were found to be nearly coincided.
Control of Mobile Manipulator for Tracking Vertical Smooth Welding Trajectory
트란디엔푹(Thien Phuc Tran),충탄람(Tan Lam Chung),김학경(Hak Kyeong Kim),김상봉(Sang Bong Kim),오명석(Myung-Suck Oh) 한국동력기계공학회 2004 한국동력기계공학회 학술대회 논문집 Vol.- No.-
This paper proposed an adaptive controller based on the back stepping concept for a two-wheel welding mobile manipulator to track a smooth curved welding path in vertical. To design a tracking controller, the tracking errors are defined between the welding point of torch and the reference point moving at a specified constant welding speed on a vertical welding path. The error for auxiliary velocity is also concerned in controller design. Both kinematic and dynamic modelings of the mobile manipulator are introduced. It is assumed for tracking controller design that the platform moves on the path paralleled for y-z plane. So, the velocity component on x-direction of the welding point equals to zero in spite of the rotation of the manipulator links. The simulations are performed to show the effectiveness of the proposed controller.
超急冷 Ni_60B_40 合金의 構造 및 熱的 安定性에 관한 硏究(Ⅰ)
具滋洛,吳明錫,林榮彦,조성석 충남대학교 공업교육연구소 1981 論文集 Vol.4 No.2
The phase transformation and structure of rapidly quenched Ni_60B_40 alloy has been studied by x-ray diffraction and electrical resistivity measurements. The first step in the transformation of rapidly quenched Ni_60B_40 alloy was found to be Am+O-Ni_4B_3+m-Ni_4B_3 → O-Ni_4B_3+m-Ni_4B_3. The mechanism of transformation has been determined by the initially present microcrystallites in the amorphous matrix. The diffusional growth has three steps of growth of a disc with constant thickness, thickening of a disc and growth in axial direction only. The activation energy for crystallization is 43㎉/mole in the first step, 57㎉/mole in the second step and 55㎉/mole in the third step.