• Transactions of Materials Processing
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• v.3 no.2
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• pp.202-214
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• 1994

An upper bound elemental technique(UBET) is applied to predict the forging load and die-cavity filling for non-axisymmetric ring forging. In order to analyze the process easily, it is suggested that 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 place-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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.837-841
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• 1997

An upper bound elemental technique(UBET) program has been developed to analyze forging load, die-cavity filling and optimum kinematically admissible velocity fields for flashless forging. The simulation for flashless forgings are applied plane and axisymmetric closed-die forging with rib-web type cavity. The kinematically admissible velocity fields for inverse triangular and inverse trapezoidal elements, are used to analyze flashless forging. Experiments have been carried out with pure plasticine billets at room temperature. Theoretical predictions of the forging load in plane-strain and axisymmetric forging are in good agreement with experimental results.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.1
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• pp.7-15
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• 1998

An upper bound elemental technique(UBET) program has been developed to analyze forging load, die-cavity filling and effective strain distribution for flash and flashless forgings. The program consists of forward and backward tracing processes. In the forward program, flash, die filling and forging load are predicted. In backward tracing process, the optimum dimensions of initial billet in conventional forging are determined from the final-shape data based on flash design. And the analysis is described for merit of flashless precision forging. Experiments are carried out with pure plasticine billets at room temperature. The theoretical predictions of forging load and flow pattern are in good agreement with the experimental results.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.3
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• pp.379-388
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• 1999

Au upper bound elemental technique(UBET) program has been developed to analyze forging load die-cavity filling and optimum kinematically admissible velocity fields for flashless forging. The simulation for flashless forgings are applied plane-strain and axisymmetric closed-die forging with rib-web type cavity. The kinematically admissible velocity fields for inverse triangular and inverse trapezoidal elements are used to analyze flashless forging,. Experiments have been carried out with pure plasticine billets at room temperature. Theoretical predictions of the forging load in plane-strain and axisymmetric forging are in good agreement with experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.205-209
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• 1994

The main purpose of this study is constructing new velocity fields on the base of shape function used in finite element method and showing the possibility of application it to metal forming processes. Utilizing the 8-node quadratic rectangular element, we expressed the velocity within the deformation region by interpolating the velocity of each nodal points. And the upper-bound formulation from this velocity fields was derived. In order to confirm the validity of this method we applied it to axisymmetic combined extrusion problem. the results of load show that this method is on better agreement with experiment than the conventional UBET, and also the flow pattern and profile of extruded part are reasonable.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.223-228
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• 1994

A new velocity formulation technique, which contains the advantage of UBET and the shape function of FEM, is proposed. In the proposed technique, a shape function is used to improve the unreasonableness of elemental partition and to solve the difficulty of velocity-field determination. In order to verify the effectiveness of this rechnique, T-shaped forging processes are simulated. The results are compared with these obtained by experimental measurements in T-shaped forging. In T-shaped forging, good agreements between theory and experiment are also confined.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.10
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• pp.57-68
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• 1995

An upper bound elemental technique (UBET) program has been developed to predict forging load, die-cavity filling, preform in non-axisymmetric forging. To analyze the process easily, it is suggested that the deformation is divided into two different parts. Those are axisymmetric part in corner, plane-strain part in lateral. The plane-strain and axisymmetric parts are combined by building block method. And the total energy is computed through combination of three deformation parts. A dumbbell-type preform has been obtained from height and volumetric compensations of the billet based on the backward simulation. Experimetns have been carried out with pure plasticine at room temperature. Theoretical predictions are in good agreement with expereimental results.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.5
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• pp.678-685
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• 1999

A UBET program is developed for determining flash the optimum sizes of preform and initial billet in plane-strain closed-die forging. The program consists of forward and backward tracing processes. In the forward program, flash, 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 based on flash design. Experiments are carried out with pure plasticine billets ar room temperature. The theoretical predictions of forging load and flow pattern are in good agree-ment with the experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.40-47
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• 1993

To diversify the area of application of UBET to the analysis of ring rolling which produces rings having more complex cross-sectional configuration, an element of triangular cross-section has been introduced and the corresponding kinematically admissible velocity field has been derived while considering the material flow between neighboring elements. The theoretical perdictions in roll torque and profile formation show good agreement with the experiments. The effect of process parameters such as feed rate and taper angle of the roll groove has been discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.2
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• pp.117-125
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• 1997

상계요소 해석(UBET) 프로그램은 비대칭 단조공정에서의 다이 충만과정과 단조 하중등을 예측하기 위하여 개발되었다. 보다 용이하게 단조 공정을 해석하기 위하여 비대칭 형상의 단조공정을 평면변형부(길이 부분)과 축대칭변형부(라운딩 부분)으로 나누었다. 평면변형부와 축대칭 변형부의 경계는 전단에너지를 고려하여 결합하는 빌딩 블록 방법(building block method)을 이용하였다. 그리고 본 연구의 비대칭 형상을 단조하는데 최적의 초기시편 형상으로 아령형의 시편(dumbbell-typed billet)을 제시하였다. 또한 실험은 상온에서 플라스티신을 사용하여 수행되었고 수치해석 결과와 실험결과는 비교적 잘 일치하였다.상계요소 해석(UBET) 프로그램은 비대칭 단조공정에서의 다이 충만과정과 단조 하중등을 예측하기 위하여 개발되었다. 보다 용이하게 단조 공정을 해석하기 위하여 비대칭 형상의 단조공정을 평면변형부(길이 부분)과 축대칭변형부(라운딩 부분)으로 나누었다. 평면변형부와 축대칭 변형부의 경계는 전단에너지를 고려하여 결합하는 빌딩 블록 방법(building block method)을 이용하였다. 그리고 본 연구의 비대칭 형상을 단조하는데 최적의 초기시편 형상으로 아령형의 시편(dumbbell-typed billet)을 제시하였다. 또한 실험은 상온에서 플라스티신을 사용하여 수행되었고 수치해석 결과와 실험결과는 비교적 잘 일치하였다.