• 한국공간구조학회논문집
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• 제12권1호
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• pp.77-85
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• 2012

막 구조물은 연성의 막에 초기 장력을 주고 외관의 강성을 늘림으로써 외부하중에 안정된 형태를 유지하는 구조물로 두께를 얇게 하여 대공간 구조에 많이 채택된다. 이러한 막 구조는 자유로운 곡선을 표현할 수 있는 특성이 있어, 구조적 형태의 선정은 매우 중요하다. 이에 본 논문에서는 넙스를 기저함수로 하는 비정형 곡면으로 형상을 표현하고, 최적의 곡면 형상 탐색을 위한 대변형 결과값 도출을 위해 기하학적 비선형을 고려한 유한요소해석법을 제안하였다. 또한, 형상 탐색 결과로 나타난 곡면의 형상 근사화의 최소화를 위해 유한 요소망으로 표현된 최종 형상을 다시 넙스로 구현하는 인터페이스 기법을 제안하여, 비정형 막 구조물의 최적 곡면을 표현하였다.

• 대한기계학회논문집
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• 제17권9호
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• pp.2223-2233
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• 1993

An engineering method is suggested to calculate the applied load versus crack extension in the elastic-plastic fracture. The condition for an increment of crack extension is set by a critical increment of crack-up opening displacement(CTOD). The ratio of the CTOD increment to the incremental crack extention is a critical crack-tip opening angle(CTOA), assumed to be constant for a material of a given thickness. The Dugdale model of crack-tip deformation in an infinite plate is applied to the method, and a complete solution for crack extension and crack instability is obtained. For finite-size specimens of arbitrary geometry in general yielding, an approximate generalization of the Dugdale model is suggested so that the approximation approaches the small-scale yielding solution in a low applied load and the finite-element solution in a large applied load. Maximum load is calculated so that an applied load attains either a limit load on an unbroken ligament or a peak load during crack extension. The proposed method was applied to three-point bend specimens of a carbon steel SM45C in various sizes. Reasonable agreements are found between calculated maximum loads and experimental failure loads. Therefore, the method can be a viable alternative to the J-R curve approach in the elastic-plastic fracture analysis.

• Journal of Welding and Joining
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• 제21권3호
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• pp.68-77
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• 2003

It is important to understand the characteristics of material strength and fracture under the dynamic loading like as earthquakes to assure the integrity of welded structures. The characteristics of dynamic strength and fracture in structural steels and their welded joints should be evaluated based on the effects of the strain rate and the service temperature. It is difficult to predict or measure temperature rise history with the corresponding stress-strain behavior. In particular, material behaviors beyond the uniform elongation can not be precisely evaluated, though the behavior at large strain region after the maximum loading point is much important for the evaluation of fracture. In this paper, the coupling phenomena of temperature and stress-strain fields under the dynamic loading was simulated by using the finite element method. The modified rate-temperature parameter was defined by accounting for the effect of temperature rise under the dynamic deformation, and it was applied to the fully-coupled analysis between heat conduction and thermal elastic-plastic behavior. Temperature rise and stress-strain behavior including complicated phenomena were studies after the maximum loading point in structural steels and their undermatched joints and compared with the measured values.

• Steel and Composite Structures
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• 제49권6호
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• pp.633-643
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• 2023

In this study, the natural frequencies of Functional Graded Materials (FGM) plates are predicted using Artificial Neural Network (ANN). A model based on Third-order Shear Deformation Theory (TSDT) and FEM is used to train the ANN model. Different training methods are tested to simulate input and output dependency. As this is a parametric model, several architectures and optimization algorithms were tested. The proposed model allows us to minimize the CPU time to evaluate candidate material properties for FGM plate material selection and demonstrate their influence on dynamic behavior. Consequently, the time required for the FGM design process (candidate materials for material selection) and the geometric optimization of the FGM structure would remain reasonable. The ANN model can help industries to produce FGM plates with good mechanical properties of the selected materials. I addition, this model can be used to directly predict vibration behavior by testing a large number of FGM plates, representing all possible combinations of metals and ceramics in today's industry, without having to solve any eigenvalue problems.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1030-1033
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• 2003

The packing-free piston has become widely distributed in certain branches of instrument making and precision machine building. A large number of the most diversified instruments are now being constructed on the principle of the packing-free piston like piston manometers, vacuum manometers, hydraulic machines, dynamometers. hardness measuring instruments. power indicators, hydraulic scales, and many others. In spite of the widespread application of systems with a packing-free piston, there were practically no special papers to the theory and practice of the application of such systems. This paper describes the theoretical approaching method to get the pressure distribution profile between the piston and cylinder using finite element method.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
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• pp.564-571
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• 1998

The function of diaphragms at abutments and piers of prestressed concrete (PSC) box girder train bridge is to transfer forces from the superstructure onto bearings or column and to stiffen the superstructure cross-section against in-plane deformation. Due to large stress disturbance at diaphragm, the design for the diaphragm using conventional design method is relatively irrational than designs for other structual members. And, due to contribution to boundary condition of deck slab by the diaphragm, the behavior of deck slab near the diaphragm is different from behavior of the deck slab obtained from two dimensional analysis of the bridge, which is basis far the design of deck slab. In this paper, three dimensional behavior of deck slab near diaphragm of PSC box girder train bridge constructed by the precast span method are analyzed by using three dimensional finite element modeling. Then, strut-and-tie model is applied to design the diaphragm of PSC box girder train bridge. The modeling techniques in this paper can be applied effectively to examine the causes of cracks at deck slab near diaphragm and to design diaphragm rationally.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1990년도 봄 학술발표회 논문집
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• pp.59-64
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• 1990

The cable structures undergo large deformation because of its highly flexibility. Therefore, we must take account of its geometric nonlinearity before analysis and find the equiribrated shape of cable structures. To solve these problems, a numerical procedures included nonlinear near theory which is applicable to general cable net, flexible transmission lines and suspended cable roofs, are presented in this paper. Now, this procedures are devided two parts : the one is to obtain the equibrated shape and stress of the cable structures applied uniform load by flexibility iteration method, the other is to analysis the equibrated structures subjected to nodal external forces by nonlinear finite element mothed. Its accuracy and efficiency are found to be comparable to some of other method and, in some aspect, it is mere applicable to cable structures.

• 한국지반공학회논문집
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• 제20권4호
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• pp.29-38
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• 2004

본 연구에서는 복합 경계면요소를 이용한 비선형 응력-변형 모델을 이용하여 쓰레기 매립지의 안정성해석을 수행하였다. 쓰레기 매립층의 응력-변형 거동 특성은 국내외 쓰레기의 삼축압축 강도시험 수행결과로써 결정하였고, 경계면 요소의 모델 변수 값은 여러 가지 차수재의 전단시험 결과를 적용하였다. 해석방법에 대한 검증을 위하여 국내 페기물 관리법에 준하는 매립지 모델을 선정하여 안정성해석을 실시하였다. 쓰레기에 대한 삼축압축시험과 토목섬유재에 대한 응력-변형 특성을 분석한 결과 쓰레기는 선형거동을 그리고 토목섬유는 비선형거동을 나타내는 것으로 나타났다. 경계면요소를 이용한 복합차수층 매립지의 안정성 해석결과 매립지 바닥면과 사면의 경계부에서 응력집중과 차수계의 전단변위가 크게 나타나 토목섬유라이너가 포설된 복합차수층의 경우는 복합 경계면 요소가 적용된 해석이 필요함을 알 수 있었다.

• Design & Manufacturing
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• 제6권1호
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• pp.73-78
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• 2012

The aim of this dissertation is inferring factors controlling the complex strain behavior of the material and the characteristics of the Fine-Blanking in the most narrow area at the shear zone where we are performing the Fine-Blanking. And also this is for inspecting and presenting their uses and the possibilities to make the results data based in order to utilize easily. Therefore, to analyze of shere zone's strain behaviour, the Fine-Blanking process need to be modelled defining the quadratic-nodded and axi-symmetrical elements as the problems of large deformation axi-symmetry and the non-linear contact. For the method of inputting strain-stress values of the material, the piece-wise linear technics were used, the Implicit-Finite Element method also used making balance of forces on each step by the long intervals, calculates and converges many times was done. The materials used for the analysis was the Steel SNCM220 5.5mm respectively. As the result of FEM analysis, we know that shear stress value in the beginning of punch penetration is distributed widely and done high both in the center of the late-thickness and on the both sides centering around shear strain zone as the punch penetration is increasing. Also.

• Steel and Composite Structures
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• 제45권6호
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• pp.907-929
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• 2022

Compression experiments were conducted to investigate the compressive behavior of built-up open-section columns consisting of four cold-formed steel channels (BOCCFSs) of different lengths, thicknesses, and cross-section sizes (OB90 and OB140). The load-displacement curves, failure modes, and maximum compression strength values were analyzed in detail. The tests showed that the failure modes of the OB90 specimens transformed from a large deformation concentration induced by local buckling to flexural buckling with the increase in the slenderness ratio. The failure modes of all OB140 specimens were deformation concentration, except for one long specimen, whose failure mode was flexural buckling. When the slenderness ratios of the specimens were less than 55, the failure modes were controlled by local buckling. Finite element models were built using ABAQUS software and validated to further analyze the mechanical behavior of the BOCCFSs. A parametric study was conducted and used to explore a wide design space. The numerical analysis results showed that when the screw spacing was between 150 mm and 450 mm, the difference in the maximum compression strength values of the specimens was less than 4%. The applicability and effectiveness of the design methods in Chinese GB50018-2002 and AISI-S100-2016 for calculating the compression strength values of the BOCCFSs were evaluated. The prediction methods based on the assumptions produced predictions of the strength that were between 33% to 10% conservative as compared to the tests and the finite element analysis.