• 소성∙가공
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• 제6권4호
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• pp.319-328
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• 1997

A flow stress involving strain, solid fraction, and breakage ratio, and solid fraction updating algorithm were proposed to depict the deformation behavior of materials at the semi-solid state. In case of isothermally simple upsetting of Sn-15%Pb alloy at the semi-solid state, by comparing the results of finite element analysis with the existing experimental results, the reliability of both the developed flow stress and updating algorithm were investigated. It was found that the verified program can effectively be used in the rigid-viscoplastic finite element analysis of the semi-solid forging processes.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.159-164
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• 1997

The optimal conditions were investigated in order to manufacture the light automotive body parts using the semi-solid forging process by the finite element nalysis. Considering about macro-segregation cause to difference of relative velocity between solid phase and liquid phase, solidificational phenomenon cause to heat transfer from die and export of the latent heat, so solid fraction updating algorithm can be proposed. The rigid thermo-viscoplastic finite element analysis was carried out according to die temperature with proposed algorithm, so availability of forming part were understood. The finite element program can be used to the analysis of semi solid forging process.

• 소성∙가공
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• 제8권4호
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• pp.399-406
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• 1999

It is more appropriate to treat that the semi-solid mixture as a single phase material that obeys incompressibility in the global sense and to analyze the liquid flow only locally than the approach based on compressible yield criteria. In the present study, a numerical algorithm of updating the solid volume fraction based on mixture theory has been developed. Finite element analysis of simple upsetting was carried out using the proposed algorithm to investigate the degree of macro-segregation according to friction conditions and compressive strain rates under the isothermal condition. The simulation results were compared to experimental results available in reference to test the validity of the currently proposed algorithm. Since the comparison results show a good agreement it is construed that the proposed algorithm can contribute to the development of numerical analysis of determining the solid volume fraction semi-solid processing.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.179-184
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• 1998

Semi-solid forging can be applied in industry only with enough knowledge of the effects of the forming parameters related with the process and their exact control which can be obtained by empirical or numerical methods. In the current study, the effects of process variables on semi-solid forging are discussed based on mainly numerical results. Die preheating temperature, initial solid fraction of the workpiece, and die velocity were selected as process variables, and numerical analyses using a rigid-thermoviscoplastic finite element approach that considered the release of latent heat due to phase change were carried out. In the analyses, a proposed flow stress material characterization and a solid fraction updating algorithm were employed. The obtained results from numerical analysis are discussed and are compared with some experimental observations.