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급곡선 주행 산악트램의 거동 특성 및 설계에 관한 연구
서승일 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.12
A mountain tram is an eco-friendly public transportation system that runs on steep and sharp mountain roads regardless of geographic and climatic conditions. It provides transportation for residents and comport mobility for tourists. In this study, the characteristic behaviors of the cars in a mountain tram on a sharp curve with 10m radius were analyzed using a theoretical method. The method's accuracy was verified with numerical results by CAD. It was also confirmed by a 1/20-scale model test. Based on this confirmation, the performance of a tram that had 3 cars and 3 bogies was reviewed, and problems with the initial design were found so that the alternatives could be presented. It was concluded that the tram passes through the sharp curve smoothly, but relative angular displacements occurred between carbodies and between a carbody and bogie. The displacements between carbodies could be absorbed by the couper's rotation, but those between the carbody and bogie generated excessive expansion of the shaft connecting the traction motor on the carbody and the reduction gear on the bogie. This caused safety issues. To solve these problems, the initial design was changed to a tram with 3 cars and 2 bogies. After the change, the displacements did not occur, and the problems were fixed. 산악 트램은 급경사와 급곡선의 산악지역 도로 위를 지형과 기후 조건에도 구애됨 없이 운행할 수 있는 친환경 대중 교통수단이다. 지역 주민에게는 교통 기본권을 보장하고, 관광객에게는 이동 편의성을 제공해 줄 수 있다. 본 연구에서는 반경10m의 급곡선을 주행하는 산악 트램 차량의 거동 특성을 이론적 방법을 이용하여 해석하고 CAD를 이용한 수치 결과를 도출한 후, 이론적 해석의 정확성을 입증하였고, 1/20 축소 모형 시험을 통해서 확인하였다. 이를 기초로 하여 3차체-3대차 구조의 산악 트램 차량 초기 설계안에 대한 성능을 확인하고 문제점을 검토하여 대안을 제시하였다. 3차체-3대차 구조의 산악 트램 차량은 급곡선을 원활하게 주행할 수 있는 차량 시스템임을 확인하였으나, 차체와 차체 사이, 차체와 대차 사이에서 상대 각변위가 발생하였다. 차체와 차체 사이의 상대 각변위는 연결기의 회전 성능으로 흡수가 가능하나, 차체와 대차 간의 상대 각변위는 차체에 붙은 견인 전동기와 대차에 붙은 감속기 사이를 연결해 주는 추진축의 과도한 신축을 발생시켜 추진축의 안전성 문제를 초래하였다. 이 문제를 해결하기 위해 3차체-2대차 구조의 차량으로 설계를 변경한 결과, 차체와 대차 사이에 상대 각변위가 발생하지 않아 문제 해결을 확인할 수 있었다.
서승일,장창두 대한용접접합학회 1997 대한용접·접합학회지 Vol.15 No.5
Deformations of structures due to welding appear much complicated and deformated modes are also complex. As parameters governing deformations are various and effect of parameters on deformations is not well known, precise prediction of deformation due to welding has been a difficult problem. Until now, many research papers as to welding deformation have been published, but the research results can explain only one aspect of welding deformation have been published, but the research results can explain only one aspect of welding deformation and are hard to be used in reasonable prediction of welding deformations in complicated structures. In this study, based on the accumulated results concerning to welding deformations, a practical method to predict complicated welding deformations of large structure is proposed. A simplified model to estimate residual plastic strains is suggested and main parameters affecting residual plastic strains are shown to be heat input and joint restaints. Inherent strain theory and experimental data are combined with the finite element method and welding deformations of large structures are calculated by elastic analysis. Comparison of calculated results with experimental data shows the accuracy and validity of the proposed method.
서승일 대한용접접합학회 2000 대한용접·접합학회지 Vol.18 No.4
Residual stresses and deformations due to welding have effects on the strength of structures. In this paper, the compressive strength of basic welded structures is studied and the effects of the residual stresses and deformations on the compressive strength of beams, plates and shells are investigated,. Theoretical analysis for the basic structures is carried out and simplified methods to calculate the compressive strength are proposed. The proposed methods yield simple formulas to calculate the compressive strength, of which results are much helpful. The accuracy of the proposed method is revealed by comparison with experimental results.
점용접 시 압흔 깊이 감소를 위한 최적 용접조건 선정에 관한 연구
서승일,이재근,장상길,차병우 대한용접접합학회 1996 대한용접·접합학회지 Vol.14 No.2
In this paper, authors are trying to find optimum spot weldig conditions to minimize indentation of the plate surface which is crucial to quality of stainless rolling stocks. At first, to derive a simple equation to estimate the depth of indentation, a simplified one-dimensional bar model is proposed and validity of the model is confirmed by experiments. And also, to find proper welding conditions giving satisfied tensile strength of the welded joint, a simple formula is derived referring to the standard spot welding conditions by AWS. Optimization problem is formulated to find welding conditions such as welding current, time and applied force which give minimum indentation and proper tensile strength of joint, and solutions are found out. According to the results, the depth of indentation can be expressed by applied electrode froces and it can be shown that an optimum applied force exists.