• 소성∙가공
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• 제9권1호
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• pp.35-42
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• 2000

In this paper, we developed the hydroforming simulator which can apply an axial compressive force and high internal pressure to bulge a tube. Experimental dtudies have been performed to investigate the effect of each parameters such as internal pressure and axial compression stroke required for the forming of circular components. Under the improper forming conditions there were two forming failures. One was the axial buckling due to excessive axial compressive load and the other was the circumferential necking fracture due to relatively high internal pressure. A safe forming zone without any failures exists between these two extreme zones. Also the condition of forming failure such as fracture is examined throughout the theoretical analysis. This paper covers a brief overview of the mechanism of hydroforming process as well as the design of die and tools.

• 한국정밀공학회지
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• 제18권6호
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• pp.109-114
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• 2001

Forming pressure of the rupture disc has been analyzed theoretically and verified by experiments. Final shape of the rupture disc after forming process is assumed to be hemi-ellipsoid for small height of the rupture disc. The predicted forming pressures are in good agreement with those by experiment. A new simple model has been proposed to predict the burst pressure of the rupture disc. Experimental results show that the proposed model of burst pressure describes the bursting characteristics of the rupture disc very well.

• 한국주조공학회지
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• 제40권2호
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• pp.34-42
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• 2020

The effects of the initial balancing pressure, filling pressure and maximum build-up pressure on the casting characteristics of the thick-wall thickness casting during the counter-pressure casting process were investigated. Water model experiment and a computer simulation were carried out to evaluate the characteristics during the filling and solidification stages in counter-pressure casting (CPC); as a reference, the low-pressure casting (LPC) process was used. The average dendrite cell size decreased with an increase in the solidification rate and maximum build-up pressure. A turbulent flow occurred during the filling stage of the LPC process, resulting in the formation of inner gas, while a lamellar flow pattern dominated during the CPC process and was more evident with an increase in the initial balancing pressure, improving the mechanical properties of the castings.

• Journal of Advanced Marine Engineering and Technology
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• 제22권4호
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• pp.460-467
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• 1998

The investigation deals with the manufacturing process design and deformation analysis for seamless pressure vessels Axisymmetric multistage deep drawing is a complex and important sheet metal forming process in the industry. In this study the process design for large size cylindrical shells with various thickness is performed and a general guideline for forming process design of pressure vessels will be suggested. Thus in this paper for the verification of the forming process design the forming analysis of pressure vessels will be carried out by PAM-STAMP which is on the basis of finite element analysis. In this case the formability of pressure vessels is evaluated using the results of computer simulation.

• 설비공학논문집
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• 제22권11호
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• pp.781-787
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• 2010

To improve the efficiency of piping, recently the pre-fabrication piping system has been introduced, and much attention has been paid to TBPs which can replace Tee-joint. Forming and forming analysis on TBPs made from Carbon steel pipes for pressure service(KS D 3562 Sch40) and Stainless steel pipes(KS D 3576 20S) have been conducted to determine working pressure. Forming and forming analysis objects are $32A{\times}25A$, $40A{\times}25A$, $40A{\times}32A$, $50A{\times}25A$, $50A{\times}32A$, $50A{\times}40A$ TBPs.

• 소성∙가공
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• 제23권2호
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• pp.116-121
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• 2014

Low pressure die casting and flow forming have been successfully used to produce sound road wheels from magnesium alloy AM80. In the current study, high speed compression testing was initially conducted to simulate the flow forming of a Mg wheel. Subsequently the flow forming was simulated with "Forge$^{TM}$", an FEM software package. On the basis of flow forming simulations, the flow forming of the Mg wheel was performed under different conditions. For the flow forming experiments, the preform castings were made by low pressure die casting from AM80, a commercial magnesium alloy. In flow forming of the magnesium preform wheel, the flow forming of the Mg wheel was successfully accomplished when the feed rate was less than half that for the forming of an aluminum road wheel. The reduction in feed rate was 52%. Finally, a comparison with the flow forming simulations was made.

• 한국정밀공학회지
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• 제22권4호
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• pp.159-166
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• 2005

This study deals with the correction of gear tooth profile error by finish roll forming. First, we experimentally confirmed that the tooth profile error is a synthesis of the concave error and the pressure angle error. Since various types of tooth profile errors appear in the experiments, we introduced evaluation parameters for rolling gears to objectively evaluate profile quality. Using these evaluation parameters, we clarified the relationship among the tooth profile error, the addendum modification factor (A. M. factor), and the tool loading force. We verified the character of concave error, pressure angle error, tool loading force and number of cycles of finish roll forming by using a forced displacement method. This study makes clear that tool loading force and number of cycles of finish roll forming are very important factors that affect involute tooth profile error. The results of the experiment and analysis show that the proposed method reduces concave and pressure angle errors.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.173-176
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• 2007

The characteristics of the tool system give many effects into the costs and qualities for the finished components. This study proposes a new method for manufacturing of high manufacturing productivity, production process reduction and low cost through back pressure forming. The Lock-up hub is manufactured through many processes, such as upsetting($1^{st}$ Forming), piercing, direct extrusion($2^{nd}$ Forming), final sizing process($3^{rd}$ Forming). In this study, process design for closed-die forging of a Lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of Lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.365-368
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• 2000

We have studies on the Microstructures and densities as a function of forming pressures and the magnetic properties of the specimens with additive Bi$_2$O$_3$ that sintered at 95$0^{\circ}C$ for 4.5 hours for synthesizing optimal Ni-Cu-Zn ferrite. Green density rose generally as Forming pressure increased from 1.7 ton/cm$^2$to 2.5 ton/cm$^2$and Cold Isostatic Pressure(CIP) method was more effective than Die Pressure(DP) method to high green density. Forming pressure had no influence on apparent density but on the other hand Bi$_2$O$_3$contents were strongly dominant to appaernt density than forming pressure. Bi$_2$O$_3$liquid phases created during sintering process promoted sintering and grain growth so that apparent density, grain size and permeability increased compared to that of the specimens which were sintered with non-additive Bi$_2$O$_3$.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.240-243
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• 2003

Finite element analyses for bursting failure prediction in bulge forming under combined internal pressure and independent axial feeding are carried out. By means of the FEM combined with Oyane's ductile fracture criterion based on Hills quadratic plastic potential, the forming limit and bursting pressure level are investigated for a seamed tube that comprises of weldment, heat affected zone(HAZ) and base material parts. Especially, in order to determine the material property of HAZ tensile tests for the base material and the weld metal are executed based on iso-strain approach. Finally, through a series of bulge forming simulations with consideration of the weldment and HAZ it is concluded that the proposed method would be able to predict the bursting pressure and fracture initiation site more realistically, so the approach can be extended to a wide range of practical bulge forming processes.