• 소성∙가공
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• 제7권5호
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• pp.426-431
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• 1998

This study is concerned with cold repressing of sintered preforms by the rotary forging process. An experiment has been carried out using the rotary powder forging press(500kN) which was designed and constructed in the authors' laboratory. The effect of process variables and aspect ration of sintered preform on the densification behavior during the rotary repressing was studied by several mechanical test such as working force hardness distribution density and microstructures of the specimens. Since a higher densification can be achieved by applying the rotary repressing on presinted preforms it was successively demonstrated that the cold rotary powder forging is an effective operation to improve quality of P/M parts.

• 소성∙가공
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• 제15권5호
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• pp.373-381
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• 2006

The key technologies necessary to develop and utilize a double-action link-type hydraulic die set for the enclosed die forging are presented in this paper. Various die sets for the enclosed die forging are investigated and the technologies necessary to develop and to utilize a double-action link-type hydraulic die set are introduced in detail with emphasis on the mechanism of the die set and its kinematical behaviors, the force transmission mechanism, the criterion on the enclosed die forging and its application, the forming load prediction and the stress distribution of the link. A double-action link-type hydraulic die set is developed and it is applied to the enclosed die forging of a bevel gear.

• 소성∙가공
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• 제32권3호
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• pp.145-152
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• 2023

The Inconel 706 alloy is a nickel-based super alloy and requires a large load for hot forging due to its excellent mechanical properties at high temperature. Rotary forging process is an innovative metal forging process where workpiece is gradually deformed by the revolving conical upper die with an inclination angle. This process allows that the workpiece is partially in contact with an upper die during the process so that the press force is considerably lower compared with the conventional upsetting process. In this study, experiments of rotary forging process and conventional upsetting process for cylindrical parts using Inconel 706 where conducted to investigate the formability of rotary forging process. And microstructure analysis and mechanical properties of Inconel 706 were performed to investigate the effect of rotary forging process on the material property.

• 소성∙가공
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• 제21권8호
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• pp.473-478
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• 2012

The yoke, a component of conventional motor-driven power steering system, often contains welding defects from its manufacturing process. To eliminate these defects, the precision cold forging process has been tried. In this study, the double-action complex forging has been used to manufacture a torsion joint yoke. The backward extrusion proved faster than the forward extrusion in forging of the product. The double-action complex forging process utilized an upper die composed of a punch, a punch guide, a disc spring and a coil spring. The forged material pushes up the punch guide, and then the disc spring and the coil spring balances the backward extrusion force. Consequently, the flow of material was essentially in the forward direction, resulting in a successful forging operation. The forging load of Al 6061-T6 was higher than that of the automotive structural hot rolled plate.

• 소성∙가공
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• 제8권4호
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• pp.384-392
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• 1999

In metal forming, there are problems with recurrent geometric characteristics without explicitly prescibed boundary conditions. In such problems, so-called recurrent boundary conditions must be introduced. In this paper, as a practical application of the proposed method, the precision cold forging of a helical gear has been simulated by a three-dimensional rigid-plastic finite element method and compared with the experiment. The application of recurrent boundary conditions to helical gear forging analysis is proved to be effective and valid. the elastic stress analysis of the die for helical gear forging has been calculated by using the nodal force at the final stage obtained from the rigid-plastic finite element analysis. In order to obtain more precise gear products, the elastic analysis of the die after release of punch and the elastic spring-back analysis of product after ejection have been performed, and the final dimension of the computational product has been in good agreement with that of the experimental product.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.119-123
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• 2009

In this paper, effects of major design parameters of cold forging dies on die mechanics are quantitatively investigated with emphasis on shrink fit using a thermoelastic finite element method. A ball-stud cold forging process found in a cold forging company is selected as a test process and the effects of die insert material, shrink fit, dimension of ring, partition of die inert and clamping force on effective stress and circumferential stress are analyzed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.281-286
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• 1997

Thin study is concerned with the cold repressing of sintered preform by rotary forging process. A experiment has been carried out using the rotary powder forging press(500kN) which was designed and constructed in the authors' laboratory. The effect of process variables and aspect ratios of sintered preform was observed and measured by several mechanical test, such as working force, hardness distribution, density, and microstructures of the specimens. It is found that the highly densified P/M parts can be obtained and this process is very effective for improving quality of the powder products.

• 한국자동차공학회논문집
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• 제14권1호
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• pp.86-91
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• 2006

Magnesium alloys have been widely used for many structural components of automobiles and aircraft because of high specific strength and good castability in spite of hexgonal closed-packed crystal structure of pure magnesium. In this paper, FE analysis was executed about the formability of AZ3l magnesium alloy on press forging process. For this, the variation of sheet temperature, distribution of punch force and the effect of heat transfer and friction between punch and sheet on the forming characteristics during press forging of AZ31 has been analyzed by finite element analysis. In order to obtain temperature dependence of material characteristics, uniaxial tension tests at elevated temperature were done under temperature of $100^{\circ}C\~ 500^{\circ}C$.

• 한국산학기술학회논문지
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• 제17권7호
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• pp.256-262
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• 2016

본 연구에서는 자동차 자동변속기의 핵심 부품인 아웃풋 허브 및 리액션 허브의 치형 미성형 구간의 최소화를 위한 배압 냉간 단조 성형 공법에 대한 유한요소해석을 수행하였다. 변위제어해석으로 펀치 하중 및 슬리브 배압력을 도출하였고, 도출된 하중 및 배압력을 이용한 하중제어해석을 수행하여 상호 검증을 하였다. 변위제어해석과 하중제어해석이 유사한 경향을 보였으며, 아웃풋 허브와 리액션 허브의 미성형 구간을 기준 이하로 만족시키기 위한 펀치 하중과 슬리브 배압력을 구하였다. 리액션 허브의 펀치 하중이 아웃풋 허브 보다 큰 이유는 상부 치형 가공 시 리액션 허브의 단면감소율이 아웃풋 허브 보다 크기 때문인 것으로 판단되며, 슬리브 배압력이 아웃풋허브와 리액션 허브에서 차이가 나는 것 또한 슬리브 단면적의 차이에 기인한 것으로 판단된다. 본 연구에서 제시한 배압 냉간 단조 성형 해석 과정과 결과를 적용한 실제 치형 가공의 미성형 구간 결과와 비교하여 검증 평가하였으며, 치형 제품의 품질 개선 및 생산성 향상을 위해 요구되는 성형가공 조건을 도출하는데 유용하게 활용될 수 있을 것이다.

• 소성∙가공
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• 제6권3호
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• pp.239-249
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• 1997

The behaviour of alloys in the semi-solid state strongly depends on the imposed stress state and on the morphology of the phase which can vary from dendritic to globular. To optimal net shape forging of semi-solid materials, it is important to investigate for filling phenomena in forging process of arbitrarily shaped dies. To produce a automotive part which has good mechanical property, the filling pattern according to die velocity and solid fraction distribution has to be estimated for arbitrarily shaped dies. Therefore, the estimation of filling characteristic in the forging simulation with arbitrarily shaped dies of semi-solid materials are calculated by finite element method with proposed algorithm. The proposed theoretical model and a various boundary conditions for arbitrarily shaped dies is investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation process with arbitrarily shaped dies is performed to the isothermal conditions of two dimensional problems. To analysis of forging process by using semi-solid materials, a new stress-strain relationship is described, and forging analysis is performed by viscoelastic model for the solid phase and the Darcy's law for the liquid flow. The calculated results for forging force and filling limitations will be compared to experimental data. The filling simulation of simple products performed with the uniform billet temperature(584$^{\circ}C$) from the induction heating by the commercial package MAGMAsoft. The initial step of computation is the touching of semi-solid material with the end of die gate and the initial concept of proposed system just fit with the capability of MAGMAsoft.