• 소성∙가공
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• 제6권5호
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• pp.446-455
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• 1997

A Combined extrusion operation consists of forward and backward extrusion forming and it is possible to make the process be simple by employing it. But the metal flow pattern induced by the operation is hard to analyze accurately because the flows are non-steady, which have at least two directions dependent upon each other. So engineers in the industrial factories had conducted the two extrusion operations separately. A new process was designed by the industrial expert for forming of an alu-minum preform using the combined extrusion operation. In this study, experiments and finite element analysis was carried out to determine the process parameters. Through the preliminary experiment, it was shown that warm forming condition was more desirable than cold or hot ones. And optimal shape of initial billet could be also determined. From the compatibility test, bonde-lube was chosen as the optimal lubricant and 20$0^{\circ}C$ as the material temperature by the inspection of micro-structure. The operation was simulated by the rigid-plastic finite element method to examine the metal flow. Disap-pearing of dead metal zone was observed as the punch fell down and desirable shape was obtained from the one operation. As a result of this study, 7 operations could be reduced and 225% of material saved.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.181-184
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• 2009

The hot press farming process, which is the press hardening of steel parts using cold dies, can utilize both ease of shaping and high strength due to the hardening effect of rapid quenching during the pressing. In this study, a thermo-elastoplastic analysis of the hot press forming process using the finite element method was performed in order to investigate the deformation behavior and temperature history during the process and the mechanical properties of the pressed parts.

• 소성∙가공
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• 제19권4호
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• pp.248-252
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• 2010

In this paper, three-dimensional finite element analysis of thread rolling process of a 12 point flange head bolt is conducted using a rigid-plastic finite element method based metal forming simulator AFDEX 3D. A whole sequence of cold forming processes of a long shaft bolt composed of four forging stages and final thread rolling process is simulated to reveal the mechanism of thread formation. A mesh density control function is applied near the major plastic deformation region to achieve computational efficiency. It has been shown both numerically and experimentally that longitudinal lengthening or shortening is negligible in thread rolling.

• 펄프종이기술
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• 제38권1호통권113호
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• pp.62-69
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• 2006

This study was carried out to measure and analyze the storage condition, distribution route, and packaging method of four selected agricultural products(small tomato, cabbage, peach, and carrot) in the cold chain system. It was shown that dew-forming phenomenon by fruits and vegetables deteriorates the agricultural product quality and physical properties of corrugated fiberboard box during the cold chain system. The compressive strength deterioration in corrugated fiberboard boxes was much greater for single wall(SW) corrugated fiberboard containers than for double wall(DW) in low temperature-high humidity condition. To reduce the deterioration of box and dew-forming phenomenon, water-repellency treatment should be over $R_6$. However, water-resistant treatment of corrugated fiberboard containers would be effective under high relative humidity conditions more than 75% RH. It was suggested that functional corrugated fiberboard box packaging would be an optimum method to reduce the deterioration of agricultural products quality by. It was also achieved controlling the relative humidity and temperature during the storage and physical distribution process.

• 소성∙가공
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• 제14권8호통권80호
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• pp.675-680
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• 2005

This study was aimed at the design of the dies for the automobile part for the engine oil leakage prevention using the computer simulation to shorten the period of production, on the basis of the process planning which was designed by the field experts. In the computer simulation,'eesy-2-form' of 2D FEM simulation package and 'eesy-DieOpt' have been used, which are the commercial process analysis and die design program. Through the simulation of 'eesy-2-form', we could know the propriety of the forming process, the inner pressure of the die and the suitable fitting pressure between the insert and the sleeve which was not showing any positive tangential stresses in the insert. Through the simulation of 'eesy-DieOpt', we could know the number of the stress ring, the diameter ratios, the stresses of the die, the shrink fitting tolerance and temperature in the condition of the already determined maximum outer die diameter of the multi-stage former. The validity of the die design using the computer simulation was analyzed by the experiments and the results were satisfactory. As the results of this study, the new and easy die design system for cold forging has been developed.

• 소성∙가공
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• 제23권4호
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• pp.211-220
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• 2014

The outer race of a constant velocity (CV) joint having six inner ball grooves has traditionally been manufactured by multi-stage warm forging, which includes forward extrusion, upsetting, backward extrusions, necking, ironing and sizing, and machining. In the current study, a multi-stage cold forging process is examined and an assessment for replacing and modifying the conventional multi-stage warm forging is made. The proposed procedure is simplified to the backward extrusion of the conventional process, and the sizing and necking are combined into a single sizing-necking step. Thus, the forging surface of the six ball grooves can be obtained without additional machining. To verify the suitability of the proposed process, a 3-dimensional numerical simulation on each operation was performed. The forging loads were also predicted. In addition, a structural integrity evaluation for the tools was carried out. Based on the results, it is shown that the dimensional requirements of the outer race can be well met.

• 소성∙가공
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• 제32권1호
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• pp.5-11
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• 2023

The aim of this study is to manufacture an aluminum pipe yoke of automotive steering system for lightweight. In a multistage cold forging process for aluminum pipe yoke, the surface defects frequently occur due to excessive deformation or friction during extrusion process for forming hollow pipe part. It is import to reduce the friction between the material and the forging die. This study investigated a multistage forging process with sliding die to reduce friction for aluminum pipe yoke. After evaluating by FE analysis, the forging experiment with the sliding die was carried out. As a result, it was possible to manufacture a sound aluminum pipe yoke.

• 소성∙가공
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• 제15권8호
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• pp.550-555
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• 2006

In this study, effects of forming angle and friction coefficient on a initiation of the Mannesmann hole defect were analyzed by using a response surface method. The maximum effective plastic strain at center point of specimen is utilized for the prediction of the starting point of crack occurrence, which is suggested by the comparison of integrals of four different ductile fracture models between the histories of the effective plastic strain at center point. It was revealed that the principal stress at the center is the dominant element to the increase of the effective plastic strain. It was also verified by the simulation results from the comparison of experiment and simulation. It is provided that the forming angle of 25 degrees and the spreading angle of 1 degree can be a proper design condition without an occurrence of internal hole defect and an excessive slip.

• 한국주조공학회지
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• 제22권5호
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• pp.231-237
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• 2002

The structure and properties of HSLA steel obtained by Osprey forming process were investigated. The porosities were generated at the bottom of specimen due to the quenching effect of cold substrate during forming. The steel had a bainitic structure. The grain size were different among positions due to the cooling rates. The elements such as Mn, S, Si, Cr, Mo and etc. were contained in inclusions. They were formed at grain boundries. The size of them was $1{\sim}2{\mu}m$ and has nothing to do with the chemical composition. MnS and NbC were precipitated during rolling and aging.

• 동력기계공학회지
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• 제6권3호
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• pp.31-35
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• 2002

Brake tube is considered one of the most important parts in automobile. The shape of brake tube end has a great influence on the function of brake, and the quality and productivity of brake tube have relation to die design. The forming process of brake tube end is performed by hydraulic press forming machine. In this paper, the forming processes of tube end for automobile is analyzed and designed to make the optimal form of brake tube end. Also, finite element analysis has been carried out using $DEFORM^{TM}% 3D to predict the optimal shape of brake tube end and the results obtained showed the optimal length between punch and chuck is $1.0{\sim}1.2mm$. The shape of tube end is in good agreement with the finite element simulations and the experimental results.