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CP-Ti 및 Ti-6Al-4V 합금의 전기화학적 특성에 미치는 제조공정의 영향
김기태 ( K. T. Kim ),조현우 ( H. W. Cho ),장현영 ( H. Y. Chang ),김영식 ( Y. S. Kim ) 한국부식방식학회 2018 Corrosion Science and Technology Vol.17 No.1
Ti and its alloys show the excellent corrosion resistance to chloride environments, but they show less corrosion resistance in HCl, H<sub>2</sub>SO<sub>4</sub>, NaOH, H<sub>3</sub>PO<sub>4</sub>, and especially HF environments at high temperature and concentration. In this study, we used the commercially pure titanium and Ti-6Al-4V alloy, and evaluated the effect of the manufacturing process on the electrochemical properties. We used commercial products of rolled and forged materials, and made additive manufactured materials by DMT (Directed Metal Tooling) method. We annealed each specimen at 760℃ for one hour and then air cooled. We performed anodic polarization test, AC impedance measurement, and Mott-Schottky plot to evaluate the electrochemical properties. Despite of the difference of its microstructure of CP-Ti and Ti-6Al-4V alloys by the manufacturing process, the anodic polarization behavior was similar in 20% sulfuric acid. However, the addition of 0.1% hydrofluoric acid degraded the electrochemical properties. Among three kinds of the manufacturing process, the electrochemical properties of additive manufactured CP-Ti, and Ti-6Al-4V alloys were the lowest. It is noted that the test materials showed a Warburg impedance in HF acid environments.
해수배관 내부 에폭시 코팅재의 캐비테이션 및 침지 열화에 따른 압입인장특성
정민재 ( M. J. Jung ),김수현 ( S. H. Kim ),전종모 ( J. M. Jeon ),김영식 ( Y. S. Kim ),김영천 ( Y. C. Kim ) 한국부식방식학회 2023 Corrosion Science and Technology Vol.22 No.6
Seawater has been used to cool devices in nuclear power plants. However, the pipes used to transport seawater are vulnerable to corrosion; hence, the inner side of pipelines is coated with an epoxy layer as prevention. Upon coating damage, the pipe becomes exposed, and corrosion progresses. The major cause is widely known as cavitation corrosion, causing the degradation of mechanical properties. In this study, corroded specimens were prepared using cavitation and immersion methods to clarify the degradation trend of mechanical properties with corrosion. Three different types of epoxy coatings were used, and accelerated cavitation procedures were composed of amplitudes of 15 μm, 50 μm, and 85 μm for 2 h, 4 h, and 6 h. The immersion periods were 3 and 6 weeks. We conducted instrumented indentation tests on all degradation samples to measure mechanical properties. The results showed that higher cavitation amplitudes and longer cavitation or immersion times led to more degradation in the samples, which, in turn, decreased the yield strength. Of the three samples, the C coating had the highest resistance to cavitation and immersion degradation.
축계용 단조강재 보수 용접부의 피로 파괴 특성에 관한 연구
김영식(Y. S. Kim),김종호(J. H. Kim),한명수(M. S. Han),손병영(B. Y. Son) 한국해양공학회 1991 韓國海洋工學會誌 Vol.5 No.1
In this paper, the fatigue strength and the fatigue crack propagation behaviors of the round bar specimens which were spirally built up by welding and subsequently hardened by quenching were investigated. The material used was SF60 which was widely employed in mechanical components, especially shafts. Fatigue tests were conducted at the fully reversed condition(R=-1) and axial and load control in the room temperature and air environment. The experimental results were expressed by both the range of stress intensity factor(ΔK) and the effective range of stress intensity factor(ΔK<SUB>eff</SUB>). It was clarified that applying of quenching after the building up welding process improved the fatigue strength and the fatigue crack propagation property in the low range of ΔK of the built up round bar specimen.
김영식(Y. S. Kim),전대원(D. W. Jun),최형식(H. S. Choi) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.10
We developed a human-sized BWR(biped walking robot) named KUBIRI driven by a new actuator based on the ball screw which has high strength and high gear ratio. KUBIRI was developed to walk autonomously such that it is actuated by small torque motors and is boarded with DC battery and controllers. To utilize informations on the human walking motion and to analyze the walking mode of robot, a motion capture system was developed. The system is composed of the mechanical and electronic devices to obtain the joint angle data. By using the obtained data, a 3-D graphic interfacer was developed based on the open inventor tool. Through the graphic interfacer, the control input of KUBIRI is performed.
김영식(Y.S.Kim),오정민(J.M.Oh),백창열(C.Y.Baik),우정재(J.J.Woo),최형식(H.S.Choi) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
We developed a human-sized BWR(biped walking robot) named KUBIR1 driven by a new<br/> actuator based on the ball screw which has high strength and high gear ratio. KUBIR1 was<br/> developed to walk autonomously such that it is actuated by small torque motors and is<br/> boarded with DC battery and controllers. To utilize the information on the human walking<br/> motion and to analyze the walking mode of robot, a motion capture system was developed.<br/> The system is composed of the mechanical and electronic devices to obtain the joint angle<br/> data. By using the obtained data, a 3-D graphic interface was developed based on the<br/> OpenGL tool. Through the graphic interface, the control input of KUBIR1 is performed.