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Ti-6Al-4V 합금의 고온 성형시 미세조직 예측에 관한 연구
이유환,신태진,박노광,심인옥,황상무,이종수,Lee You Hwan,Shin Tae Jin,Park No Kwang,Shim In Ok,Hwang Sang Moo,Lee Chong Soo 한국군사과학기술학회 2004 한국군사과학기술학회지 Vol.7 No.4
A study has been made to investigate the high temperature deformation behavior of Ti-6Al-4V alloyand to predict the final microstructure under given forming conditions. Equiaxed and $Widmanst\ddot{a}tten$ microstructures of Ti-6Al-4V alloys were prepared as initial microstructures. By performing the compression tests at high temperatures$(700\~1100^{\circ}C)$ and at a wide range of strain rates$(10^{-4}\~10^2/s)$, various parameters such as strain rate sensitivity(m) and activation energy(Q) were calculated and used to establish constitutive equations. When the specimens were deformed up to strain 0.6, equiaxed microstructure did not show any significant changes in microstructure, while $Widmanst\ddot{a}tten$ microstructure revealed considerable flow softening, which was attributed to the globularization of a platelet at the temperature range of $800\~970^{\circ}C$ and at the strain rate range of $10^{-4}\~10^{-2}/s$. To predict the final microstructure after forming, finite element analysis was performed considering the microstructural evolution during the deformation. The grain size and the volume fraction of second phase of deformed body were predicted and compared with the experimental results.
백서 심장 및 현장독성에 대한 Doxorubicin 과 Epirubicin 의 영향
박유환(You Hwan Park),정희상(Hoe Sang Jung),김완중(Wan Jung Kim),권희식(Hee Sik Kwon),김용태(Young Tae Kim),문철웅(Chul Oong Moon),박찬국(Chan Kook Park),이승일(Seung Il Lee),홍순표(Soon Pyo Hong) 대한내과학회 1991 대한내과학회지 Vol.41 No.3
Doxorubicin is an antibiotic of the anthracycline group which has proven effective in treating a variety of malignant disorders. Its use in cancer chemotherapy has been limitd, however, because of the its cardiotoxic side effects. Attempts to reduce the cardiotoxicity of anthracycline antibotics include the synthesis of structural analogs, e.g., epirubicin, the coupling of active drugs to carriers, and the discovery of new types of anthracyclines. In this experiment, the toxicity of epirubicin was examined in various organs of rats for levels of malondialdehyde and activity of free radical scavengers (superoxide dismutase and catalase) and compared with the toxicity of doxorubicin. The following results were obtained: 1) Doxorubicin increased the quantity of malondiadehyde by 519% (p<0.01) in the heart, 45% (p<0.01) in the kideny, 35%(p<0.05) in the lung, and 41% (p<0.05) in the liver. Epirubicin increased the quantity of malondiadehyde by 10%(p<0.05) in the heart and 26%(p<0.01) in the kidney, but there was little change in the lung and liver. 2) Doxorubicin and Epirubicin decreased the activities of catalase in the heart by 11% and 17% but increased the it in the kidney by 27% and 19%, respectively (p<0.05). 3) Doxorubicin and Epirubicin increased the activities of SOD in the heart by 24% (p<0.01) and 199%(p<0.05) and in the kidney by 23%(p<0.01) and 34% (p<0.05) respectively. In conclusion, Epirubicin shows less toxicity in the heart than the kidney and has less cardiorenal toxicity in rats compared to Doxorubicin for same doses.
신태진,이유환,염종택,홍성석,박노광,심인옥,이종수,황상무,Shin Tae-Jin,Lee You-Hwan,Yeum Jong-Taek,Hong Sung-Suk,Park No-Kwang,Shim In-Ok,Lee Chong-Soo,Hwang Sang-Moo 한국군사과학기술학회 2004 한국군사과학기술학회지 Vol.7 No.2
Titanium alloys are vital elements for developing advanced structural components, especially in aerospace applications. However, process design for successful forming of titanium alloys is a difficult task, which has to be achieved within a very narrow range of process parameters. In this paper is a finite element based optimal design technique is presented and applied to volume fraction optimization process design in backward extrusion of titanium alloys.
Ti-6Al-4V합금의 열간 후방압출에 대한 성형 안정성 평가모델의 고찰
염종택,박노광,이유환,신태진,황상무,홍성석,심인옥,이종수,Yeom Jong-Taek,Park Nho-Kwang,Lee You-Hwan,Shin Tae-Jin,Hwang Sang-Mu,Hong Sung-Suk,Shim In-Ok,Lee Chong-Soo 한국군사과학기술학회 2004 한국군사과학기술학회지 Vol.7 No.3
The metal forming behavior of Ti-6Al-4V tube during hot backward extrusion was investigated with various forming stabilities or instabilities criteria. that is, Ziegler's instability criterion, dynamic materials model(DMM) stability criteria and Rao's instability criterion. These approaches also were coupled to the internal variables generated from FE simulation. In order to validate the reliabilities of three criteria, hot backward extrusions for Ti-6Al-4V tube making were carried out with different backward extrusion designs. The useful model for predicting the forming defects was suggested through the comparison between experimental observations and simulation results.