• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.425-428
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• 2009

Silicone is recently used for LED chip encapsulment due to its good thermal stability and optical transmittance. To mold a solid-state silicone encapsulment, curing by mixing at elevated temperatures followed by cooling is necessary. As the silicone molding process is involved in healing and subsequent cooling, the thermal residual stress, which causes mechanical warpage or optical birefringence in the final silicone encapsulment, may be induced if there are non-uniformities in cured silicone material properties or encapsulment shape design. The prediction of residual stress is necessary to design a high-quality silicone molding process. Therefore, in the present paper, a numerical parametric study was attempted to evaluate the heating and cooling effects on the thermal residual stress induced in the cured silicone.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.863-874
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• 2009

The engineering characteristics and the reinforcement effect of the elephant foot method were discussed with parametric study. The elephant foot method is adopted to support the loads transferred from tunnel crown and improve bearing capacity of elephant foot in poor ground condition. The evaluation of reinforcement effect, which has the mechanical relationship between ground condition, footing size and reinforcement system, was carried out through the previous research and numerical analysis. In addition, the simple design chart was proposed to estimate the applicability of the elephant foot reinforcement method. It will be practical for the engineer to determine the optimum reinforcement method for safe tunnelling in soft ground condition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.12
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• pp.1245-1254
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• 2001

For a R410A-rolling piston type rotary compressor model which was modified by reducing the cylinder height and shaft eccentricity from R22-compressor version, numerical simulation has been carried out and simulation results have been found to be compared fairly well with those of measurements. EER of this first version of R410A compressor was 4.8% lower than that of R22 compressor. To improve the performance of the R410A compressor model, parametric study on the design parameters related to the discharge port system has been performed by using the numerical simulation program, and optimum conditions for the highest EER have been obtained with the aid of Taguchi method. With the optimized discharge port configuration, EER has been improved by 1.7%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.1
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• pp.1-9
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• 2002

The thermal response of electronic components during infrared reflow soldering is studied by a two-dimensional numerical model. The convective, radiative and conduction heat transfer within the reflow oven as well as within the card assembly are simulated. Parametric study is also performed to determine the thermal response of electronic components to various conditions such as conveyor velocities, exhaust velocities and emissivities. The results of this study can be used in selecting the oven operating conditions to ensure proper solder melting and minimization of thermally induced card assembly stresses.

• Structural Engineering and Mechanics
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• v.11 no.1
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• pp.49-70
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• 2001

This paper is concerned with a study on thermo-elastoplastic characteristics of functionally graded composite. Compared to the classical layered composites, it shows a wide range of thermo-elastoplastic characteristics according to the choice of two major parameters, the thickness-wise volume fraction of constituents and the relative thickness ratio of the graded layer. Therefore, by selecting an appropriate combination of the two parameters, one is expected to design the most suitable heat-resisting composite for a given thermal circumstance. Here, we address the parametric investigation on its characteristics together with theoretical study on thermo-elastoplasticity and numerical techniques for its finite element approximations. Through the numerical experiments, we examine the influence of two parameters on the thermo-elastoplastic characteristics.

• Advances in nano research
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• v.10 no.5
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• pp.493-507
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• 2021

This article focused on studying the buckling behavior of two-dimensional functionally graded (2D-FG) nanosize tubes, including porosity based on first shear deformation and higher-order theory of tube. The nano-scale tube is simulated based on the nonlocal gradient strain theory, and the general equations and boundary conditions are derived using Hamilton's principle for the Zhang-Fu's tube model (as higher-order theory) and Timoshenko beam theory. Finally, the derived equations are solved using a numerical method for both simply-supported and clamped boundary conditions. The parametric study is performed to study the effects of different parameters such as axial and radial FG power indexes, porosity parameter, nonlocal gradient strain parameters on the buckling behavior of di-dimensional functionally graded porous tube.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.307-313
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• 2019

In order to design efficient Urea Decomposition Chamber (UDC) for the Low Pressure (LP) Selective Catalytic Reduction (SCR) system, numerical simulations were conducted with respect to various design parameters. The design parameters examined in this simulation include the chamber diameter, inlet and outlet shape of chamber, and urea injection point. Reaction kinetics for the urea decomposition was proposed and validated with the experimental data in the range of $300{\sim}450^{\circ}C$. The effects of design parameters on the performance of UDC were evaluated by the calculated urea conversion and pressure drop. As a result, the local optimum design values were derived by the parametric study.

• Journal of Welding and Joining
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• v.11 no.3
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• pp.34-47
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• 1993

Finite element models were developed for thermal and residual stress analysis for the specific welding problems. They were used to evaluate the effectiveness of the various welding heat input models, such as ramp heat input function and lumped pass models. Through the parametric studies, thermal-mechanical modeling sensitivity to the ramp function and lumping techniques was determined by comparing the predicted results with experimental data. The kinetics for residual stress formation during welding can be developed by iteration of various proposed mechanisms in the parametric study. A ramp heat input function was developed to gradually apply the heat flux with variable amplitude to the model. This model was used to avoid numerical convergence problems due to an instantaneous increase in temperature near the fusion zone. Additionally, it enables the model to include the effect of a moving arc in a two-dimensional plane. The ramp function takes into account the variation in the out of plane energy flow in a 2-D model as the arc approaches, travels across, and departs from each plane under investigation. A lumped pass model was developed to reduce the computation cost in the analysis of multipass welds. Several weld passes were assumed as one lumped pass in this model. Recommendations were provided about ramp lumping techniques and the optimum number of weld passes that can be combined into a single thermal input.

• Structural Engineering and Mechanics
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• v.64 no.1
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• pp.59-69
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• 2017

The field of fracture mechanics has gained significance because of its ability to address the behaviour of cracks. Predicting the fracture properties of concrete based on experimental investigations is a challenge considering the quasi-brittle nature of concrete. So, there is a need for developing a standard numerical tool which predicts the fracture energy of concrete which is at par with experimental results. The present study is an attempt to evaluate the fracture energy and characteristic length for different grades of concrete using Concrete Damage Plasticity (CDP) model. Indian Standard and EUROCODE are used for the basic input parameters of concrete. Numerical evaluation is done using Finite Element Analysis Software ABAQUS/CAE. Hsu & Hsu and Saenz stress-strain models are adopted for the current study. Mesh sensitivity analysis is also carried to study the influence of type and size of elements on the overall accuracy of the solution. Different input parameters like dilatation angle, eccentricity are varied and their effect on fracture properties is addressed. The results indicated that the fracture properties of concrete for various grades can be accurately predicted without laboratory tests using CDP model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.367-370
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• 2007

Present study examines detonation wave propagation characteristics in annular channel. A normalized value of channel width to the annular radius was considered as a geometric parameter. A parametric study was carried out for a various regimes of detonation waves from weakly unstable to highly unstable detonation waves. Numerical approaches that used in the previous study of numerical requirements of the simulation of detonation wave propagations in 2D and 3D channel were used also for the present study with OpenMP parallization for multi-core SMP machines. The major effect of the curved geometry on the detonation wave propagation seems to be a flow compression effect, regardless of the detonation regimes. The flow compression behind the detonation wave by the curved geometry of the circular channel pushes the detonation wave front and results in the overdriven detonation waves with increased detonation speed beyond the Chapmann-Jouguet speed. This effect gets stronger as the normalized radius smaller, as expected. The effect seems to be negligible beyond the normalized radius of 10.