• KIEAE Journal
• /
• v.10 no.4
• /
• pp.75-80
• /
• 2010

Generally, ground-source heat pump (GSHP) systems have a higher performance than conventional air-source systems. However, the major fault of GSHP systems is their expensive boring costs. Therefore, it is important issue that to reduce initial cost and ensure stability of system through accurate prediction of the heat extraction and injection rates of the ground heat exchanger. Conventional analysis methods employed by line source theory are used to predict heat transfer rate between ground heat exchanger and soil. Shape of ground heat exchanger was simplified by equivalent diameter model, but these methods do not accurately reflect the heat transfer characteristics according to the heat exchanger geometry. In this study, a numerical model that combines a user subroutine module that calculates circulation water conditions in the ground heat exchanger and FEFLOW program which can simulate heat/moisture transfer in the soil, is developed. Heat transfer performance was evaluated for 3 different types ground heat exchanger(U-tube, Double U-tube, Coaxial).

• Transactions of Materials Processing
• /
• v.10 no.7
• /
• pp.525-533
• /
• 2001

PET bottles are main]y manufactured by the stretch blow-molding process. In order to improve the thickness distribution to avoid crack generation at bottom region of one-piece PET bottle, process analysis of stretch blow-molding using a finite element method has been carried out. Finite element analysis has been carried out using ABAQUS/Standard. CREEP user subroutine provided in ABAQUS has been used to model PET behavior that is rate sensitive. Among the process parameters, the effect of plunger movement to thickness distribution of bottle has been considered by axisymmetric analysis. A modified process of plunger movement, which yields more uniform thickness distribution, has been proposed. 3D FE analysis has been done to confirm the validity of the proposed process.

• 한국전산유체공학회:학술대회논문집
• /
• 2010.05a
• /
• pp.99-102
• /
• 2010

In the present study, a three-dimensional numerical simulation was performed in a paint drying system of vehicle assembly line. In the drying system hot air and cool air are blown in turn from the nozzles to dry the trim of vehicle. Inlet boundary condition using user subroutine code is adopted to consider the moving motion of the vehicle. The present paper aims to improve the performance of the drying system. The transient distribution of temperature and velocity at the surface of the vehicle were predicted numerically. From these results, optimal operating condition of the drying system are to be suggested.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2004.10a
• /
• pp.278-281
• /
• 2004

In this paper, the thermomechanical responses of shape memory alloy (SMA) actuators and their applications as the shape adaptive structures combining SMA actuators produced in the form of strip with composite structures are investigated. The numerical algorithm of the 3-D SMA thermomechanical constitutive equations based on Lagoudas model is implemented to analyze the unique characteristics of SMA strip. Also, the incremental SMA constitutive equations are implemented in the user subroutine UMAT by using ABAQUS finite element program. The shape change of structure is caused by initially strained SMA strip bonded on the surface of the composite structure when thermally activated. Numerical results show that SMA strip actuator can generate enough recovery force to deform the composite structure and sustain the deformed shape subjected to large external load, simultaneously.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.7
• /
• pp.930-939
• /
• 2004

Constitutive models for final stage densification of metal powder compacts with power-law creep deformation were investigated. The constitutive models were implemented into a finite element program (ABAQUS) by using user subroutine CREEP and, from FEM results, useful densification curves were obtained when hydrostatic and uniaxial stress were applied to the powder compacts at various pressures and temperatures. Because the densification behavior varied as the constitutive models, the equivalent stress surface on each constitutive equation was investigated to analyze the difference of densification behavior.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.596-599
• /
• 1997

In this study, the flow control system with shape memory alloy in jet engine inlet was suggested to adjust the shock boundary layer interact~on for supersonic flight system. It consisted of the flap with shape memory alloy, spar with steel, and fixing device with aluminum alloy. The advantages of itself are a simple configuration, a passive air circulation by using the flap deflection due to pressure difference, and no need to be required the auxiliary devices. Finite element analysis was conducted to predict the thenno-mechanical behavlor of the flap system with shape memory alloy. The user-defined subroutine UMAT was implemented with ABAQUS to accon~modate the thermo-mechanical constitutive relation of shape memory alloy.

• Journal of the Korean Society for Railway
• /
• v.9 no.6 s.37
• /
• pp.778-783
• /
• 2006

This study investigates the ultimate behavior of reinforced concrete beams by means of practical nonlinear finite element (FE) analyses. Uniaxial constitutive models for the concrete and steel material are selected in this study. The adopted material model is integrated into the ABAQUS fiber beam elements through a user-defined material subroutine (UMAT). Within a developed nonlinear finite element framework, the FE results have been compared to experimental results reported by other researchers. It has been found that the proposed finite element model is capable of predicting the initial cracking load level, the yield load, the ultimate load, and the crack distribution with acceptable accuracy.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.6
• /
• pp.178-188
• /
• 2003

A study on the dynamic analysis of a tracked vehicle for mining on deep-sea bed with very soft soil is presented. An equation for the interaction between track and soft soil is employed to develop a track/soil interaction module called TVAS. The vehicle is modeled as a multi-body dynamic system using a multi-body dynamic analysis program. The developed module is incorporated into the multi-body dynamic analysis program with a user subroutine. The dynamic behavior and design of the mining vehicle on deep-sea bed is investigated.

• 한국전산유체공학회:학술대회논문집
• /
• 2011.05a
• /
• pp.112-116
• /
• 2011

In this paper, a preconverter of MCFC for an emergence electric power supplier is numerically simulated to increase the hydrogen production from natural gas (methane). Commercial code is used to simulated the porous catalyst with user subroutine to model three dominant chemical reactions which are Stream Reforming(SR), Water-Gas Shift(WGS), and Direct Stram Reforming(DSR). To get 10% fuel conversion rate in preconverter. the required external heat flux is supplied from outer wall of preconverter. The calculated results show that very nonuniform temperature distribution and chemical reaction happen near the wall of preconverter. These phenomena can be explained by the low heat conductivity of porous catalyst and the endothermic reforming reaction.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.305-310
• /
• 2008

This paper provides the methods to estimate the burst pressures of the pipes with defects, based on finite element analyses. FE codes are frequently adopted for the simulations of the burst tests of the pipes with defects. However, those do not give the burst pressure directly. Because the post-processing should be followed; determination of the fracture strains in accordance with triaxialities, monitoring the strains of pipes, etc. In the present work, these efforts are implemented in the user subroutine UHARD within the general-purpose FE code, ABAQUS. Four fracture criterions are introduced to estimate the burst pressure of pipes, and a simple fracture strain estimate is also developed. FE analyses for the pipe with gouge and corrosion are performed, and the results are compared with the experiment results.