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김홍규(H.K. Kim),김종덕(J.D. Kim),허영무(Y.M. Heo) 한국소성가공학회 2011 금형가공 심포지엄 Vol.2011 No.9
Magnesium alloy sheet has a relatively low formability compared to other commercial structural metals though it is press-formed at elevated temperatures to improve the press formability. In general, the formability of magnesium alloy sheet is known to depend on temperature as well as strain-rate imposed on the material, and the accurate prediction of the formability considering the dependence is crucial to design the forming process of magnesium alloy sheet parts. Some different type failure criteria for warm press forming are proposed based on the ductile fracture criteria, flow stress, and effective strain. And the proposed criteria are compared with each other by being applied to magnesium alloy in the present study. Considering the temperature and strain-rate sensitivity of magnesium alloy at elevated temperatures, the effects of temperature and strain-rate have are essentially incorporated into the failure criteria. The relative the effects of temperature and strain-rate have are essentially incorporated into the failure criteria. The relative performances of failure criteria are evaluated based on the comparison with the experimental warm deep drawing test using magnesium alloy AZ31 sheets. From the comparison, we explore the strength and weakness of each failure criteria proposed in the present study.
김홍규(H.K. Kim),박경엽(K.Y. Park),송기동(K.D. Song) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.10
This paper presents the prediction method of small current interruption performance for EHV gas circuit breakers. The FVFLIC method is used for the gas flow analysis and the FEM for the electric field analysis. Then. the dielectric withstanding voltage is evaluated by the empirical formulation or Streamer theory. By comparing the calculated dielectric strength with the test result. it is found that both methods show good prediction capability for the small current interruption performance. Especially. when both methods predict the same interrupting performance. the prediction is in accordance with the experimental result.