• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04a
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• pp.620-625
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• 1995

Finite element analysis tool was developed to analyze the casting process. Generally, casting processes consists of mold filling and solifification. In order to investigate the effects of process variables and to predict the defects, both filling and solidiffication process were simulated simultaneously. At filling process, especiallywe consider thermal coupling to investigate thermal history of material during the filling stage. And thermal condition at the final stage of filling is used as the initial conditions in a solidification process for the exact simulation of the actual casting processes. At mold filling process, Lagrangian-type finite element method with automatic remashing scheme was used to find the material flow. To avoid numerical instability in low viscous fluid, a perturbation method with artificial viscosity is adopted. At solififfication process, enthalpy-based finite element method was used to solve the heat transfer problem with phase change. And elastic stress analysis has been performed to predict the thermal residual stress. Through the FE analysis, solidiffication time, position of solidus line, liquidus line and thermal residual stress are studied. Finite element tools developed in this study will be used process design of casting process and maybe basic structure for total CAE system of castigs which will be constructed afterward.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.213-216
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• 2008

Sled test id widely used to evaluate the performance of occupant's safety system in frontal crash environment without having to conduct a full-scale crash test. Steel bar breaking system is used to generate deceleration profile which is experienced by passengers in frontal crash. In this study, deformation analyses of steel bars were conducted using a commercial FE code. Several guidelines were proposed to improve the accuracy of simulation.

• Advances in Computational Design
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• v.2 no.4
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• pp.333-348
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• 2017

Inspections of ancient metallic bridges have illustrated fatigue cracking in riveted connections. This paper presents a comparison between two alternative finite element (FE) models proposed to predict the fatigue strength of a single shear and single rivet connection. The first model is based on solid finite elements as well as on contact elements, to simulate contact between the components of the connection. The second model is built using shell finite elements in order to model the plates of the riveted connection. Fatigue life predictions are carried out for the shear splice, integrating both crack initiation and crack propagation lives, resulting from the two alternative FE models. Global fatigue results, taking into account several clamping stresses on rivet, are compared with available experimental results. Proposed comparisons between predictions and experimental data illustrated that the proposed two-stage model yields consistent results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.207-210
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• 2006

Behavior of dynamic/static recrystallization during hot deformation of Cast alloy 718 was investigated. For this purpose, hot compression test and FE-simulation were conducted via Thermecmaster-Z and DEFORM-3D, respectively. The microstructural evolution during hot compression and post heat-treatment was investigated and deformation mechanism were analyzed by stress-strain curve, FE-simulation and microstructure. FE-simulation results show that the temperature difference between top-die and billet has considerable influence on the final shape of compressed specimen. The relation between applied load and processing time was predicted by the FE-simulation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.4
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• pp.36-44
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• 2020

This study analyzed the deformation behavior of the high density polyethylene (HDPE) bottle in the blow molding process. We carried out finite element (FE) simulations using ANSYS Polyflow. First, the axisymmetric model was executed by 2D FE-simulation to determine the change of bottle wall thickness during the molding process. Then, the square model of the bottle was executed by 3D FE-simulation to gauge the effects of gas pressure on the change of wall thickness. The experiment results showed that the FE-simulations were able to upgrade the quality of the HDPE bottle in the blow molding process. These results can be used as guidance in adjusting gas pressure, as well as be extended for further study to determine process parameters such as temperatures, forming velocity, parison shape, etc.

• Transactions of Materials Processing
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• v.17 no.6
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• pp.429-435
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• 2008

In this paper, the serrated forming process is analyzed with finite element method. The seal should secure the overlapping portions of ligature, which has teeth for ligature to prevent from slipping each other after clamping. In the simulation, rigid-plastic finite element model has been applied to the serration forming process. Serration or teeth forming characteristics has been analyzed numerically in terms of teeth geometry based on different forming conditions. Analyses are focused to find the influence of different die movements and geometries on the tooth geometry, which is crucial for securing overlapping portions of ligature. Two major process variables are selected, which are the face angle and entry angle of punch, respectively. Extensive investigation has been performed to reveal the influences of different entry and face angles on the geometry of teeth formation in the simulation. Three different face angles of punch have been selected to apply to each simulation of serrated sheet forming process with every case of punch entry angles. Furthermore, tooth geometries predicted from simulation have been applied to the indention process for comparing proper tooth geometries to secure the sealing.

• Steel and Composite Structures
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• v.21 no.2
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• pp.323-342
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• 2016

To study the effect of collar-plate reinforcement on the static strength of tubular T-joints under axial loading, fundamental research work is carried out from both experimental test and finite element (FE) simulation. Through experimental tests on 7 collar-plate reinforced and 7 corresponding un-reinforced tubular T-joints under axial loading, the reinforcing efficiency is investigated. Thereafter, the static strengths of the above 14 models are analyzed by using FE method, and it is found that the numerical results agree reasonably well with the experimental data to prove the accuracy of the presented FE model. Additionally, a parametric study is conducted to analyze the effect of some geometrical parameters, i.e., the brace-to-chord diameter ratio ${\beta}$, the chord diameter-to-chord wall thickness ratio $2{\gamma}$, collar-plate thickness to chord wall thickness ratio ${\tau}_c$, and collar-plate length to brace diameter ratio $l_c/d_1$, on the static strength of a tubular T-joint. The parametric study shows that the static strength can be greatly improved by increasing the collar-plate thickness to chord wall thickness ratio ${\tau}_c$ and the collar-plate length to brace diameter ratio $l_c/d_1$. Based on the numerical results, parametric equations are obtained from curving fitting technique to estimate the static strength of a tubular T-joint with collar-plate reinforcement under axial loading, and the accuracy of these equations is also evaluated from error analysis.

• Transactions of Materials Processing
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• v.17 no.3
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• pp.170-181
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• 2008

The shape of rectangular cup used for Ni-MH(Nickel-coated Metal Hydrogen) battery for hybrid car looks quite simple, but the forming process of extruding and setting up process design are highly difficult. Furthermore, there are few concrete reports on the rectangular deep drawn cup as part of hybrid vehicles till now. In this study, process design for rectangular cup in the multi-stage deep drawing process is carried out, and FE analysis is also preformed based on the result of the process design. From the simulation result, some unexpected problems such as earing, wrinkling and excessive thickness changes of the intermediate blank occurred. To overcome these failures, a series of modification for punch shape in the forming process design are completed and applied. Considering the modified punch shape in the multi-stage deep drawing process, additional FE analysis is also carried out and the simulation result is verified in view of the deformed shape, thickness change and effective strain distribution. The result of FE analysis with the improved process design confirmed not only reducing thinning of wall and possibilities of failure but also improving the quality of drawing product through the modification of punch shape.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.10-22
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• 1998

In the present work the elastic-plastic FE formulations using dynamic explicit time integration schemes are used for numerical analysis of a large auto-body panel stamping processes. For analyses of more complex cases with larger and more refined meshes, the explicit method is more time effective than implicit method, and has no convergency problem and has the robust nature of contact and friction algorithms while implicit method is widely used because of excellent accuracy and reliability. The elastic-plastic scheme is more reliable and rigorous while the rigid-plastic scheme require small computation time. In finite element simulation of auto-body panel stamping processes, the roobustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry conditions. The performnce of the dynamic explicit algorithms are investigated by comparing the simulation results of formaing of complicate shaped autobody parts, such as a fuel tank and a rear hinge, with the experimental results. It has been shown that the proposed dynamic explicit elastic-plastic finite element method enables an effective computation for complicated auto-body panel stamping processes.

• Transactions of Materials Processing
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• v.20 no.8
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• pp.581-587
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• 2011

The production of high-precision micro-sized screws, used to fasten parts of micro devices, generally utilizes a cold thread-rolling process and two flat dies to create the teeth. The process is fairly complex, involving parameters such as die shape, die alignment, and other process variables. Thus, up-front finite-element(FE) simulation is often used in the system design procedure. The final goal of this paper is to produce high-precision screw with a diameter of $800{\mu}m$ and a thread pitch of $200{\mu}m$ (M0.8${\times}$P0.2) by a cold thread rolling process. Part I is a first-stage effort, in which FE simulation is used to establish process parameters for thread rolling to produce micro-sized screws with M1.4${\times}$P0.3, which is larger than the ultimate target screw. The material hardening model was first determined through mechanical testing. Numerical simulations were then performed to find the effects of such process parameters as friction between work piece and dies, alignment between dies and material. The final shape and dimensions predicted by simulation were compared with experimental observation.