• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.279-280
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• 2007

In this study, it is investigated that the effect of material properties such as various temperature, forming speed and strain rates on formability and forming limits of Mg alloy sheet in square cup deep drawing. Since the sheet metal forming of Mg alloy is perform at elevated temperature, the effect of strain rates related with the forming temperature and forming speed is very important factor for formability and forming limits. Therefore, the investigation for process variables is necessary to improve formability and forming limits. Also, the effects of strain rate and thickness transformation were studied by the experimental and FE analysis using the square cup deep drawing. The temperature, forming speed, and strain rates were investigated. Forming of Mg alloy takes consider into temperature, proper forming speed and strain-rate the formed parts were good without defects fur forming limits.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.299-304
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• 2008

This paper presents plastic limit loads of piping branch junctions with local wall thinning under combined pressure and in-plane bending, based on systematic three-dimensional finite element limit analyses using elastic-perfectly plastic materials. An ideal branch junction without weld or reinforcement around the intersection is considered with two locations of wall thinning; one in the run pipe, and the other in the branch pipe. Based on FE results, effects of thinning geometries on plastic limit moments are quantified and simple approximations of plastic limit loads are proposed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.3
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• pp.304-310
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• 2004

In this paper, cracking threshold for nanoindentation is analyzed by using 3D finited-element method. The analysis by maximum principal stress criterion can obtain the reliable results for determining to crack initiation location and load. Because the ratio of maximum principal stress to indentation depth for Victors indentation is smaller than flat-plane-column indentation and cracking for Victors indentation occurs from the inner part of specimen difficult to measure crack length, the nanoindentation facture test for flat-plane-column indentation is more effective.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.351-356
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• 2001

A potential loss of structural integrity due to aging of nuclear piping may have a significant effect on the safety of nuclear power plants. In particular, failures due to the erosion and corrosion defects are a major concern. As a result, there is a need to assess the remaining strength of pipe with erosion/corrosion defects. In this paper, a limit load solution for the eroded and corroded SA106 Grade B pipes subjected by internal pressure is developed. based in 3-D finite element analyses, considering a wide range of the shape of pipeline, flaw depth and axial flaw length parametrically.

• Transactions of Materials Processing
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• v.6 no.4
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• pp.300-310
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• 1997

A finite element inverse method is introduced for direct prediction of blank shapes, strain distributions, and reliable intermediate shapes from desired final shapes in axisymmetric multi-step deep drawing processes. This mothod enables the determination of process disign. The approach deals with the Hencky's deformation theory. Hill's second order yield criterion, simplified boundary conditions, and minimization of plastic work with constraints. The algorithm developed is applied to motor case forming, and cylindrical cup drawing with the large limit drawing ratio so that it confirms its validity by demonstrating resonably accurate numerical results of each problem. Numerical examples reveal the reason of difficulties in motor case forming with corresponding limit diagrams.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.131-138
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• 2015

In this paper, the modified live-load and designed formula are studied according to the fact the highway bridge design specifications are recently revised. The two examples for composite steel plates and PSC girder bridges are studied. The envelope is analyzed with the finite element models and lateral load distribution method applying the existing highway bridge specification(2010), the newly revised highway bridge specification(2015) and AASHTO LRFD. In case of composite steel plates, length changes between spans are studied, and in case of PSC girder. changes of the number of cross-beams and spans, and span-lengths, are analyzed.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.69-76
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• 2010

The majority of research that has been performed on cracking potential of concrete by shrinkage has assumed that concrete acts as a homogeneous material. However, with this approach, it is not able to evaluate the micro-cracking behavior in concrete due to autogenous shrinkage under unrestrained boundary condition (free boundary condition) nor to understand the cracking behavior properly because of the heterogeneous nature of concrete. To better understand the micro-cracking behavior of concrete induced by autogenous shrinkage, series of experiments were performed measuring the length change and acoustic emission energy. As an analytical approach, this research uses an object oriented finite element analysis code (OOF code) to simulate the behavior of the concrete on a meso-scale. The concrete images used in the simulations were directly obtained from mortar samples. From the experiments and simulation results, it was able to better understand the micro-cracking behaviour of concrete due to shrinking of paste phase and internal restraint by aggregates.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.97-102
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• 2007

Though the stability analysis of soil slopes widely employs the limit equilibrium method, the study on the jointed rock slopes must consider the direction of joint and the characteristics of Joint at the same time. This study analyzes the result of the change in the factors which show the characteristics of discontinuity and the shape factor of rock slopes, and so on, in an attempt to validate the propriety as to the interpretation of jointed rock slope stability which uses the general finite element program. First, the difference depending on the flow rules was compared, and the factor effect study was conducted. The selected independent variables included the direction of joint which displays the mechanical characteristics of discontinuity, adhesive cohesion, friction angle, the inclination and height of rock slope which reveal the shape of slope and surcharge load. And the horizontal displacement was numerically interpreted at the 1/3 point below the slope, a dependent variable, to compare the relative degree of factor effects. The findings of study on factor effects led to the validation that the result of horizontal displacement for each factor satisfied various engineering characteristics, making it possible to be applied to stability interpretation of jointed rock slope. A modelling is possible, which considers the application of the result of real geotechnical surveys & laboratory studies and the non-linear characteristics when designing the rock slope. In addition, the stress change which may result from the natural disaster, such as precipitation, and the construction, can be expressed. Furthermore, as the complicated rock condition and the ground supporting effect can be considered through FEM, it is considered to be very useful in making an engineering decision on the cut-slope, reinforcement and so on.

• Journal of Korean Society of Steel Construction
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• v.22 no.2
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• pp.109-119
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• 2010

There are many restrictions in the application of high-strength HSSs, including yield strength and yield ratio for the 600-MPa steel. The AISC and Canadian codes recommend that the yield strength and yield ratio of HSS members be 360 MPa and 80%, respectively. It is important to understand the true buckling behaviors of HSSs using high-strength steel at the limit states. There are many experimental data regarding the rectangular HSSs, and the circular ones are not enough for high-strength steel. Therefore, this study was conducted to create a better understanding of the buckling behaviors of the 600- and 400-MPa steels based on the results of the finite-element analysis that was done before the experiment. To understand the structural behaviors of the aforementioned steels, the width-to-thickness ratios, the angle of the web members, the yield strength, and the gap of the web members were selected as the main parameters in this study, and ABAQUS, a general finite-element program, was used.As a result, the compression web member reached elastic buckling in the 600-MPa steel and inelastic buckling in the 400-MPa steel. A brittle fracture occurred in the case where the yield ratio was greater than 80%. At the same time, it was found that the limit strength determined via FEM analysis had a higher value compared to the code evaluation with the variation of the width-to-thickness ratio in the main code member. The change in the connection load in high-strength steels was not identified by the other factors.

• The Journal of Engineering Geology
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• v.12 no.3
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• pp.345-360
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• 2002

This study was for analysing the sedimentary rock slope stability and providing the reinforcement method that can heighten stability. The study area consists of Cretaceous basalt or basaltic tuff belonging to Hak-Bong Basalt Formation in Ha-Yang Group. Nature of geological structure confirmed in this area ars bedding, joint and fault. Majority of geological structure that affect most relationship rock slope stability is bedding. It is shown that dip direction is 120~160/15~25. In other structure, joint sets are shown that dip direction of set 1 is 310~330/65~85 and set 2 is 230~250/70~85. Joint set 3 shows above 85$^{\circ}$ high angle on NE trend although do not show clear. Stability analysis about rock slope used kinematic analysis, limit equilibrium method and FLAC by numerical analysis method. FLAC is continuum model that use Fintie Defferentce Method, but could use Interfaces Module and get discrete model's analysis effect such as UDEC.