• 한국정밀공학회지
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• 제14권8호
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• pp.92-100
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• 1997

An upper-bound elemental technique (UBET) analysis is carried out to improve the material flow and to reduce the load of bearing-race forming process. The UBET analysis, which adapts the advantages of stream function and finite element method, is useful for predicting the profile of complex geometric bound- ary. From the UBET analysis, the forming load, the velocity distribution and the stream line of the deformed billet are determined by minimizing the total power consumption with respect to chosen parameters. The results of present UBET analysis are better than those of previous UBET analysis. Experiments have been carried out with model material plasticine billets at room temperature. The theoretical predictions for forming load and flow pattern(stream line) are in good agreement with the experimental results.

• 한국정밀공학회지
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• 제12권9호
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• pp.126-136
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• 1995

Copper magnetron anode of a microsave-over consists of an cylindrical outer-tube and various inner-vanes. The magnetron anode is produced by the complex processes; vane blanking, pipe cutting and silver-alloy brazing of vanes. Recently, the backward extrusion process for forming vanes has been developed to avoid the complex procedures. The developed process is analyzed by using upper-bound elemental technique (UBET). In the UBET analysis, the upper-bound load, the configuration and the vane-height of final extruded product are determined by minimizing the roral power consumption with repect to chosen parameters. To verify theoretical analysis, experiments have been carried out with pure plasticine billets at room temperature, using different web-thickness and number of vanes. The theoretical predictions both for forming load and vane-height are in reasonable agreement with the experimental results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.204-208
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• 1995

Copper magnetron anode of a microwave-oven consists of an cylindrical outer-tube and various inner-vanes. The magnetron anode is produced by the complex process ; vane blanking, pipe cutting and sliver-alloy brazing of vanes. Recently, the backward extrusion process for forming vanes has been developed to avoid the complex procedures. The developed process is analyzed by using upper-bound elemental technique(UBET). In the UBET analysis, the upper-bound load, the configuration and the vane-height of final extruded product are determined by minimizing the total power consumption with respect to chosen parameters. To verify theoretical analysis, experiments have been carried out with pure plasticine billets at room temperature, using different web-thickness and number of vanes. The theoretical predictions both for forming load and vane-height are in reasonable agreement with the experimental results.

• 대한기계학회논문집
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• 제13권3호
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• pp.337-344
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• 1989

본 연구에서는 플래쉬(flash)를 가진 축대칭 리브-웨브형(rib-web type) 제품의 형단조가공을 해석하기 위한 UBET 프로그램을 개발하고 변형중의 경계 조건처리를 다르게 한 세 가지 유동모델에 대하여 소재의 유동상태와 단조하중을 계산하여 효과적인 유동모델을 제시하였다. 또한 체적은 같으나 반지름과 높이의 비가 다른 몇 가지 초기소재 형상에 대하여 변형에 따른 소재의 다이충만도 및 하중을 비교하여 적절한 초기소재의 형상을 찾고자 하였다. 본 연구에서 제시한 유동모델의 효율성을 검증하기 위하여 플라스씬(plasticine) 소재를 사용한 실험과 그 결과를 비교, 분석하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.177-181
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• 1996

A fundamental study for the production of an internal combustion engine piston by forging is performed through UBET(Upper Bound Elemental Technique) analysis and experiments. In UBET analysis, an optimal preform of the aluminum piston is predicted and the results are compared with the experimental results. The internal flow pattern and and the forging loads according to the different friction condition are investigated.

• 한국정밀공학회지
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• 제18권6호
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• pp.174-181
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• 2001

An upper bound elemental technique(UBET) has been carried out to predict the forming load, the deformation pattern and the extrude length of the lateral extrusion of a spider for the automotive universal joint. For the upper bound analysis, a kinematically admissible velocity field(KAVF) is proposed. From the proposed velocity field, the upper bound load, the deformation pattern and the average length of the extruded billets are determined by minimizing the total energy consumption rate which is a function of unknown velocities at each element. Experiments are carried out with antimony-lead billets at room temperature using the rectangular shape punch. The theoretical prediction of the forming load, the deformation pattern and the extruded length are good in agreement with the experimental results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.1129-1133
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• 2001

An upper bound elemental technique(UBET) has been carried out to predict the forming load, the deformation pattern and the extruded length of the lateral extrusion of a spider for the automotive universal joint. For the upper bound analysis, a kinematically admissible velocity field(KAVF) is proposed. From the proposed velocity field, the upper bound load, the deformation pattern and the average length of the extruded billets are determined by minimizing the total energy consumption rate which is a function of unknown velocities at each element. Experiments are carried out with antimony-lead billets at room temperature using the rectangular shaped punch. The theoretical prediction of the forming load, the deformation pattern and the extruded length are good in agreement with the experimental results.

• 한국정밀공학회지
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• 제11권5호
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• pp.134-142
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• 1994

An upper bound elemental technique (UBET) is applied to predict variations of neutral plane and optimal position of the initial billet for rib-wep shaped ring forging. In the analysis, the neutral plane position and velocity fields are determined by minimizing the total power consump- tion with respect to chosen parameters. The degree of die-cavity filling by initial billet-position and the variations of neutral plane by friction condition are investigated. Experiments have been carried out with pure plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agrement with the experimental results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 춘계학술대회 논문집
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• pp.63-70
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• 1994

An upper bound elemental technique(UBET) is applied to predict forging load and die-cavity filling for non-axisymmetric ring forging. The finial product is divided into three different deformation regions. That is axisymmetric part in corner, lateral plane-strain part and shear deformation on boundaries between them. The plane-strain and axisymmetric part are combinded by building block method. Also the total energy is computered through combination of three deformation part. Experiments have been carried out with pure plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agreement with the experimental results.

• 대한기계학회논문집
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• 제18권5호
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• pp.1117-1125
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• 1994

A UBET program is developed for determining the optimum sizes of preform of a rib-web part in axisymmetric closed-die forging. The program consists of forward and backward tracing processes. In forward process, material flow, degree of die filling, and forging load are predicted. In backward tracing process, the optimum dimensions of initial billet and preform are determined from the final-shape data without flash. The above program is easy to handle input data with and is convenient to visualize the whole process of closed-die forging with. Experiments are carried out with pure plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agreement with the experimental results.