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Kyung-Shin Choi(최경신),Sang-Hoon Lee(이상훈),JeongJu Choi(최정주) 한국기계가공학회 2021 한국기계가공학회지 Vol.20 No.3
The size of container ships is increasing to increase the cargo loading capacity. However, container ships are limited in terms of the hull longitudinal strength. To overcome this limitation, brittle crack arrest steel can be used. This study was aimed at examining the influence of the heat input on the welding procedures of flux cored arc welding and submerged arc welding. In the experiment, the crack tip opening displacement test, which pertains to a parameter of fracture mechanics, was performed, and a 3-point bending tester was adopted. Based on the results, the crack measurement method was presented, and the stress expansion coefficient value for the pre-fatigue crack length was derived according to the heat input after the pre-cracking length was measured. It was noted that the heat input affected the crack tip opening displacement of brittle crack arrest steel.
Study of Brittle Crack Propagation Welding for EH40 Steel Plate in Shipbuilding Steel
Kyung-Shin Choi(최경신),Sang-Hoon Lee(이상훈),Won-Jee Chung(정원지),Hui-Geon Hwang(황희건),Seok-Han Hong(홍석한),Ji-Ung Hong(홍지웅) 한국기계가공학회 2019 한국기계가공학회지 Vol.18 No.5
Recent economic trends are worsening and becoming longer, and Korean shipbuilding is focused on high value added and high technology, especially for LNG carriers and large container ships. Both ship types increased in size in the 2010s but have requirements such as high strength, toughness at low temperatures and continuous weldability for preventing brittle fractures at service temperatures. In particular, as container ships become larger, the International Classification Society (IACS) has established a provision (IACS UR S33) that mandates the use of BCA (Brittle Crack Arrest) certified vessels for large container vessels contracted after 2014 to ensure safety. Therefore, studies on BCA 47Y.P are currently being undertaken, but BCA 40Y.P has not been actively studied yet. We will test BCA 40Y.P to verify why it can be applied to a large container ship and measure fatigue cracking.
Kyung-Shin Choi(최경신),Ji-Han Lee(이지한),Ji-Ung Hong(홍지웅),Won-Jee Chung(정원지) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.7
Container vessels continue to grow in size, led by global shipowner. Large ships can be loaded more cargo at a time, reducing the cost of transportation per teu. this eventually leads to economies of sale, in which the production cost per unit decreases with increasing output. in accordance with the 70th Convention of the Marine Environment Protection Committee of the International Maritime Organization, as of January 1, 2020, MARPOL Annex Ⅵ Regulation 14.1.3 will be effective. All vessels must be meet these criteria to reduce Sox emissions and reduce NOx emissions by reducing the content of manned sulfur oxides from 3.5% to less than 0.5%, otherwise IACS Member States Entry to the port is denied. in order to do that need to LNG storage tank. in this study characteristic of the material after line heating (600℃,700℃,800℃,900℃) of 9% Ni steel used in the manufacture of LNG fuel tank of ship were verified using by mechanical test. In the heating method by line heating. The initial properties of steel are changed by variables such as temperature, time, speed. The experimental data of line heating presented in this paper confirmed that the initial change of 9% Ni steel could be minimized.
Lifting Lug by the Change of form Using Multivariate Functions: An Optimal Design Study
Kyung-Shin Choi(최경신),Ji-Jun Kim(김지준),Ji-Han Lee(이지한),Gwang-Woo Chan(천광우) 한국기계가공학회 2021 한국기계가공학회지 Vol.20 No.4
In this paper, we proposed an optimal design for determining the shape of a lifting lug freely by applying a multivariate function to the D-type lug, which is commonly used in shipyards. We derived the optimal aspect ratio of the lug through structural analysis and analyzed the safety and behavior of the lug aspect ratio. As a result, two types of final candidates, both lighter than the existing lug weight, were suitable for the ratio. They were found to have the greatest force at an angle of 45 degrees when a load of 100 tons was imposed. When the horizontal and vertical feature ratio of the lug was 1:3, it showed excellent results in terms of safety rates while maintaining weight reduction and functional aspects.
A Study on the Structural Integrity of Lifting Lug without Appendage
Kyung-Shin Choi(최경신),Ji-Jun Kim(김지준),JeongJu Choi(최정주) 한국기계가공학회 2021 한국기계가공학회지 Vol.20 No.11
In this study, a multivariate function was applied to the genetic algorithm for D-type lugs currently used in shipyards to closely analyze the behavioral form of weight loss without double plates. An optimal lifting lug structure design without attachments is proposed. MATLAB R2016a was used to design features by applying multivariate functions to genetic algorithms. Furthermore, the design was achieved by deriving the optimal shapes of lugs using genetic algorithms. The shapes of the designed lugs were validated for structural bonding using the structural analysis program ANSYS 2020 R2, and a robust design of lugs with no appendages was developed.
1993 토레몰리노스 의정서의 시행을 위한 IMO의 동향
유영종,최기중,최경신,Yoo, Young-Jong,Choi, Kee-Jung,Choi, Kyung-Shin 선박안전기술공단 2010 선박안전 Vol.29 No.-
어선 안전에 관한 국제 협약인 1977 어선안전을 위한 토레몰리노스 국제협약 및 1993 토레몰리노스 의정서는 현재 그 발효요건이 충족되지 못하여 전 세계적으로 발효되지 못하고 있는 실정이다. 이에 국제해사기구(IMO)는 의정서 요건을 완화하는 "1993 토레몰리노스 의정서 시행에 관한 협정서 개발"을 해당 전문위원회인 복원성, 만재흘수선, 어선안전 전문위원회에서 제53차 회의('11. 01)까지 그 초안 작업을 완료하고 제27차 총회에서 이를 채택할 계획으로 논의를 진행하고 있다. 따라서 이러한 국제적인 움직임에 대응하고 동 의정서 시행에 대비하여 우리나라에 미치는 파급효과를 최소화하기 위한 활동의 일환으로써 본 연구는 그 동안 IMO에서 추진하여 왔던 활동과 그 내용을 담고 있다.
A Study on the Development of Hall Effect Sensor for Hydraulic Locking Alarm in Ship’s Steering Gear
Jung-Min Lee(이정민),Won-Jee Chung(정원지),Dong-Jae Lim(임동재),Kyung-Shin Choi(최경신) 한국기계가공학회 2019 한국기계가공학회지 Vol.18 No.1
The LVDT (Linear Variable Displacement Transducer) type sensor used for the existing ship"s steering gear is simple on / off that does not perform proportional control operation to the control & unloading device. When the main spool is located at both extremes, It is reflected in the price by using an expensive sensor for import. In this paper, the Hall Effect Sensor is applied to Hydraulic Locking Alarm to analyze classification rules, structure, characteristics and operation principle of valves, and research on localization development in terms of cost reduction. The comparative analysis of the existing prototypes and the cause analysis of the problems were carried out, and the structural analysis showed satisfactory results within the allowable stress range. In addition, it was verified through experiments that the actual operation is realized by applying the actual developed product, and it was confirmed that the load on the maximum value exceeds the allowable maximum load even in the case of the universal tensile test in preparation for the departure of the rod casing.