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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.
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.
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.
급곡선 급경사 선로를 주행하는 산악트램의 차체 상호 거동에 대한 이론적 해석 및 연결기 설계에 관한 연구
서승일,김정국,연제훈 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.12
Mountain trams are an all-weather public transportation system that can operate on roads in mountainous regions. Manufacturing a mountain tram that can run safely on sharp curves and steep slopes requires an understanding of the characteristic behaviors of the carbodies and the design of a coupler that can sufficiently absorb the relative deformations between the carbodies. This paper presents the theoretical equations for carbodies on a curve or a spiral track to analyze the pitching, yawing, and rolling displacements caused by the relative rotational deformation of the carbodies. Numerical analysis was performed using a CAD to verify the accuracy and validity of the presented theoretical equations. Simple theoretical equations can quickly identify the effects of various changes in design variables on the behaviors of the carbodies. For a mountain tram under development, a coupler absorbing the relative behaviors of the carbodies was designed based on the results of carbody behavior analysis. The coupler can absorb pitching, yawing, and rolling displacements between the carbodies into in-plane and out-of-plane rotational deformations. Applying the designed coupler will allow mountain trams to run safely and smoothly on sharp curves and steep slopes.
서승일,장창두 대한용접접합학회 1990 대한용접·접합학회지 Vol.8 No.2
Analytic solutions of heat conduction during welding which were first found by Resenthal have some restrictions. One of these is that models to which analytic solutions can be applied must have simple geometric shape, and another is that quasi-stationary state must be created. On the other hand, computational methods developed recently with the aid of the computer can overcome these shortcomings, but the methods raise problems from economic point of view when they are applied to 3 dimensional problems. Taking account of these problems, a new method combinig the analytic method with the computational one is proposed. This method can be ued in weldments with complicated geometric shape in non-stationary state, but with the aid of the analytic method can reduce the computing time.