• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.16-29
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• 1995

A full three-dimensional thermo-coupled rigid-viscoplastic finite element method and the currently developed microstructural evolution system which includes semi-empirical mathematical equations suggested by different research groups were used together to form an integrated system of process and microstructure simulation of hot rolling. The distribution and time history of thermomechanical variables such as temperature, strain, strain rate, and time during pass and between passes were obtained FEM analysis of multipass hot rolling processes. Then distribution of metallurgical variables were calculated successfully on the basis of instantaneous thermomechanical data. For the verification of this method the evolution of microstructure in plate rolling and shape rolling was simulated and their results were compared with the data available in literature. Consequently, this approach makes it passible to describe the realistic evolution of microstructure by avoiding the use of erroneous average value and can be used in CAE of multipass hot rolling.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.03a
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• pp.203-210
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• 1995

The rapid progress of automobile industry has led to a demand for sheet metal products and the new forming technology for complex product is required. In Deep Drawing process of steel sheet, especially stainless steel sheet at room temperture, some intermediate annealing need to be added to lessen strain hardening effect. The present study is concerned with the wram deep drawing of stainless steel sheet. In order to reduce the number of working process. the limit drawing ration is considered as main parameter. In this study, the effect of process variables such a sblank holder force, working temperature and lubricant on limit drawing ration is investigated . Experiments are carried out for the hemisherical and sqare shape at room and warm temperature respectively. The drawing loads and thickness deviation accoring to process variables measured . As the result of apploying those experimental data to the commerical butt product, the number of process can be reduced and good quality of products can be obtained.

• Journal of Korean Association for Spatial Structures
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• v.17 no.4
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• pp.69-76
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• 2017

For evaluating equations of bursting force in different codes, comparative study of the formulas was conducted. Because the equations does not consider variables such as shape of anchorages, angle of tendons, and eccentricity, a relation between the bursting forces and the variables has to be analyzed. In this paper, therefore, a comparative analysis of bursting forces computed by equations in the codes and finite element analysis was performed. As a result, it could be figured out that bursting force equations in the local zone were determined by coefficient k.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.4
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• pp.317-326
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• 2008

The main purpose of the present study is to perform shape optimizations of transonic compressor blade in order to enhance its performance. In this study, the Latin hypercube sampling of design of experiments and the weighted average surrogate model with the help of a gradient based optimization algorithm are used within design space by the lower and upper limits of each design variable and for finding optimum designs, respectively. 3-D Reynolds-averaged Navier-Stokes solver is used to evaluate the objective functions of adiabatic efficiency and pressure ratio. Six variables from lean and airfoil thickness profile are selected as design variables. The results show that the adiabatic efficiency is enhanced by 1.43% by efficiency optimization while the pressure ratio is increased very small, and pressure ratio is increased by 0.24% by pressure ratio optimization.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.159-162
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• 2007

This study presents a numerical procedure to optimize the shape of a staggered dimpled surface to enhance the turbulent heat transfer in a rectangular channel. A optimization technique based on neural network is used with Reynolds-averaged Navier-Stakes analysis of the fluid flow and heat transfer with Shear Stress Transport turbulence model. The dimple depth-to-dimple print diameter ratio, channel height-to-dimple print diameter ratio, and dimple print diameter-to-pitch ratio are chosen as design variables. The objective function is defined as a linear combination of terms related to heat transfer and friction loss with a weighting factor. Latin Hypercube Sampling is used to determine the training points as a mean of the Design of Experiment. Optimal values of the design variables were obtained in a range of the weighting factor.

• Transactions of Materials Processing
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• v.18 no.3
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• pp.245-250
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• 2009

A lid & frame used as the shield of electromagnetic waves in cellular phones are composed of frame, which is welded at their electric circuits, and lid, of which debonding and joining are available from the frame. Typical lid & frame were mechanically bonded by contact between the embossing of lid and the piercing of frame. Bonding force of this part has to allow us to detach the lid from frame for exchange or fix of the electric part and have to be high enough to protect the electric part from external impacts. This study is designed to estimate the effect of design variables of lid & frame on its debonding force. Estimations were performed by finite element method.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.30-37
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• 2005

A drum clutch which is a main part for the automatic transmission of auto-mobiles has been manufactured by glob threading and machining. The tooth shape of the drum clutch manufactured by machining has lower dimensional accuracy than that by pressing and its machining needs the enormous cost at plant investment. Thus, this study was designed to develop cold forging process and to improve the productivity and dimensional accuracy. In this work, variables affecting dimensional accuracy were first determined, then cold forming process design according to each variables was performed by FE simulation. Optimal process was suggested on the basis of analytical results.

• Journal of Communications and Networks
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• v.5 no.3
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• pp.240-248
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• 2003

This paper analyzes mobile agent performance in network management compared to the client-server model used in the Simple Network Management Protocol (SNMP). Prototypes of an application that gathers MIB-II (Management Information Base-II) variables have been created and tested on a LAN. After acquiring implementation parameters related to network management and to the mobile agent infrastructure, simulation results have been obtained on large topologies similar in shape to the Internet. Response time results show that mobile agents perform better than SNMP when the number of managed elements ranges between two specific limits, an inferior bound and a superior one, determined by the number of messages that pass through a backbone and by the mobile agent size which grows along with MIB-II variables collected on network elements. The results also show that a significant improvement is achieved when the mobile agent returns or sends data to the management station after visiting a fixed number of nodes.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.223-228
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• 2007

The profile ring rolling process of Ti-6Al-4V alloy was investigated by finite element(FE) simulation and experimental analysis. The process design of the profile ring rolling includes geometry design and optimization of process variables. The geometry design such as initial billet and blank sizes, and final rolled ring shape was carried out with the calculation method based on the uniform deformation concept between the wall thickness and ring height. FEM simulation was used to calculate the state variables such as strain, strain rate and temperature and to predict the formation of forming defects during ring rolling process. Finally, the mechanical properties of profiled Ti-6Al-4V alloy ring product were analyzed with the evolution of microstructures during the ring rolling process.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1303-1308
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• 2008

This paper presents effects of impeller geometrical parameters on the performance of a centrifugal pump impeller. The effects of meridional parameters and vane plane development parameters on the performance of the impeller were numerically studied using a commercial CFD code and DOE(design of experiments) software. Geometrical parameters in a method of meridional view and vane plane development were selected and defined to generate the 3D impeller shape. The response variables are defined in a total head and efficiency curve with flow rate. The influences of selected design variables on the various objective functions were examined as a result of the calculation using 2k factorial.