• 소성∙가공
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• 제12권7호
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• pp.668-674
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• 2003

Rigid-plastic finite element analyses on the deformation of slabs at various width reductions have been performed. By using commercial finite element code, dog-bone profile, crop profile and the longitudinal width profile after edging and Horizontal rolling have been analysed. The deformation behavior of slab for the heavy edger mill has also been compared with that for the sizing press. From the deformation analyses, it was found that the sizing press-horizontal rolling method is more efficient in width reduction than that of heavy edger mill-horizontal rolling. The results of finite element analyses fer the deformation of slab were well confirmed by the actual operational data. It was found that the amount of width variation after sizing and rolling is about 5∼10mm.

• 한국지진공학회논문집
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• 제8권2호
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• pp.19-25
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• 2004

일반적으로 운동방정식을 풀기 위해 많이 이용되는 선형근사모델은 계산이 용이한 반면에 큰 변형상태에서는 그 오차가 커지는 단점이 있다. 따라서 엄밀한 구조물의 응답해석을 위해서는 물성과 기하에 대한 비선형성을 고려해야 한다. 또한, 강과 같이 연성이 큰 재료는 소성 변형을 일으키면서 소산되는 에너지의 대부분이 열로 변하게 되며, 이 열은 열역학 제1 법칙과 2 법칙에 따라 다른 부분으로 전달된다. 이렇게 전달된 열은 온도를 상승시켜 재료의 강도를 약화시키는 역할을 하며, 이것이 다시 구조물의 응답에 영향을 미친다. 본 논문에서는 지진 등의 큰 하중을 받거나 화재로 인한 열 하중을 받는 강구조물의 비선형 대 변형 현상을 적절히 해석할 수 있는 열-탄소성 물성모델을 제안하고 3차원 유한요소해석을 수행하려다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 연약지반처리위원회 학술세미나
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• pp.79-92
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• 2000

In this paper, comparison of the observed and the predicted ground deformations due to the construction of road embankment with peck drain near the construction site was made. Measurement of the ground deformation at the gasoline stand due to the construction of road embankment was made and it was compared with the predicted deformation results of Finite Element Method analysis made with Elasto-plastic and Elastic visco-plastic models. A well agreement was obtained between the measured and predicted ground deformations.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권12호
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• pp.540-545
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• 2005

The transformer tank is pressurized by atmosphere at the time of vacuum oiling and, plastic deformation occurs at the section of stress concentration on transformer tank at this time. It is important to predict where the sections of stress are in order to prevent deformation and to add reinforcement. This paper presents prediction results where the sections of stress are occurred and whether plastic deformation occur or not, using structure analysis program(ANSYS-design program).

• Journal of Welding and Joining
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• 제28권2호
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• pp.39-46
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• 2010

IIn this study, used is the equivalent loading method based on the inherent strain to predict the welding deformation of panel members. Equivalent loads are computed from the inherent strain distribution around weld line, and then applied for the linear finite element analysis. Thermal deformation of panel members can be, of course, carried out through the rigorous thermal elasto-plastic analysis procedure but it is not practical in applying to predicting the welding deformation of large structures such as blocks found in a ship structure from view of computing time. The present equivalent load approach has been applied to flat plate model to verify the present approach, and to several curved plate models having the curvature in the welding direction to investigate the effect of the longitudinal curvature upon the weld-induced deformation. The results are compared with those by thermal elasto-plastic analysis. As far as the present results are concerned, it can be said that the present approach shows good agreement with the results by welding experiment and the rigorous thermal elasto-plastic analysis. The present approach has been also applied to predict the welding deformation of panel block as for application illustration to practical model.

• 한국정밀공학회지
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• 제30권1호
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• pp.120-127
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• 2013

A novel severe plastic deformation process named half channel angular extrusion (HCAE) is proposed in order to produce bulk UFG materials. In HCAE process, equal channel angular extrusion (ECAE) and conventional forward extrusion process is integrated to increase the strain per pass and effectiveness of the SPD process. Three-dimensional finite element analysis was carried out to study the deformation behavior of the materials in the HCAE process. HCAE process was performed experimentally on commercially pure aluminum (AA1050) and micro-Vickers hardness test was used to measure the distribution of hardness on the section of normal to the extrusion direction. The results show that HCAE is able to impose more intensive strains per pass and give rise to higher micro-hardness than ECAE.

• 대한기계학회논문집
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• 제18권7호
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• pp.1738-1750
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• 1994

Both cylindrical cup drawing and square cup drawing are analyzed using membrane analysis as well as shell analysis by the elastic-plastic finite element method. An incremental formulation incorporating the effect of large deformation and normal anisotropy is used for the analysis of elastic-plastic non-steady deformation. The computed results are compared with the existing experimental results to show the validity of the analysis. Comparisons are made in the punch load and distribution of thickness strain between the membrane analysis and the shell analysis for both cylindrical and square cup drawing processes. In punch load, both analyses show very little difference and also show generally good agreement with the experiment. For the cylindrical cup deep drawing, the computed thickness strain of a membrane analysis, however, shows a wide difference with the experiment. In the shell analysis, the thickness strain shows good agrement with the experiment. For the square cup deep drawing, both membrane and shell analyses show a wide difference with experiment, this may be attributable to the ignorance of the shear deformation. Concludingly, it has been shown that the membrane approach shows a limitation for the deep drawing process in which the effect of bending is not negligible and more exact information on the thickness strain distribution is required.

• 대한기계학회논문집A
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• 제24권7호
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• pp.1740-1747
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• 2000

Under repeated rolling, initial plastic deformation introduces residual stresses which render the steady cyclic state purely elastic. This is called the process of shakedown. Many studies have been done about the shakedown in semi-infinite half space using calculated Hertizian pressure. In this paper shakedown processes in a shaft are studied by finite element analyses of a two dimensional(plane strain) model with elastic-linear-kinematic-hardening-plastic material subjected to repeated, frictionless rolling contact. Symmetric and non-symmetric pressure distributions are obtained using a simplified model of the bearing-shaft assembly. The rolling contact is simulated by repeatedly translating both pressure distributions along the surface of the shaft. By the influence of the non-symmetric pressure, larger residual radial tensile stress is generated in the immediate subsurface layer, which may make a crack propagate and, the subsurface undergoes a zigzag plastic deformation during the shakedown process, which may lead to a crack initiation.

• 대한금속재료학회지
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• 제48권7호
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• pp.598-604
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• 2010

Tensile tests are widely used for evaluating mechanical properties of materials including flow curves as well as Young's modulus, yield strength, tensile strength, and yield point elongation. This research aims at analyzing the plastic flow behavior of high strength steels for automotive bodies using the finite element method in conjunction with the viscoplastic model considering the yield point elongation phenomenon. The plastic flow behavior of the high strength steel was successfully predicted, by considering an operating deformation mechanism, in terms of normalization dislocation density, and strain hardening and accumulative damage of high strength steel using the modified constitutive model. In addition, the finite element method is employed to track the properties of the high strength steel pertaining to the deformation histories in a skin pass mill process.

• 대한금속재료학회지
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• 제46권3호
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• pp.144-149
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• 2008

Equal channel angular pressing (ECAP) has been studied intensively over the decade as a typical top-down process to produce ultrafine/nano structured materials. ECAP has successfully been applied for a processing method of severe plastic deformation to achieve grain refinement of magnesium and to enhance its low ductility. However, difficult-to-work materials such as magnesium and titanium alloys were susceptible to shear localization during ECAP, leading to surface cracking. The front pressure, developed by Australian researchers, can impose hydrostatic pressure and increase the strain level in the material, preventing the surface defect on workpiece. In the present study, we investigated the deformation and fracture behavior of pure magnesium using experimental and numerical methods. The finite element method with different ductile fracture models was employed to simulate plastic deformation and fracture behavior of the workpiece.