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류한선,김지훈,이명규,김돈건,이형림,정관수,윤재륜,강태진,Ryou Hansun,Kim Ji Hoon,Lee Myoung-Gyu,Kim Dongun,Lee Hyung Rim,Chung Kwangsoo,Youn Jae Ryoun,Kang Tae Jin The Korean Fiber Society 2005 한국섬유공학회지 Vol.42 No.5
In order to describe the mechanical behavior of highly anisotropic and asymmetric materials such as fiber reinforced composites, the elastic-plastic constitutive equations were used based on the recently developed yield criterion and hardening laws. As for the yield criterion, modified Drucker-Prager yield surface was used to represent the orthotropic and bi-modular (asymmetric) properties of composite materials, while the anisotropic evolution of back-stress was used to account for the hardening behavior. Experimental procedures to obtain the material parameters of the hardening laws and yield surface are presented for 3D braided glass fiber reinforced composites. For verification purposes, finite element simulation results based on the proposed constitutive laws have been compared with measurements for the three point bending tests.
김준형,류한선,Michael. L. Wenner,정관수,정경환,이원오,공진학,김대용,김종민 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.5
Finite element simulations were performed for the sequential procedures of bending and hydro-forming of DP590 tubes in order to optimize the process parameters, in particular, the boost condition and axial feeding in the sequential forming processes considering formability and spring-back. The effects of the material property, including strain-rate sensitivity on formability as well as spring-back were also evaluated numerically. As for the constitutive law, the isotropic hardening law was used along with the non-quadratic anisotropic yield function, Yld2000-2d. Forming limit diagrams were calculated based on Hill’s bifurcation theory and the MK theory. In order to characterize the material properties, tensile tests were performed for both the DP590 sheet and tube. Finite element simulations were performed for the sequential procedures of bending and hydro-forming of DP590 tubes in order to optimize the process parameters, in particular, the boost condition and axial feeding in the sequential forming processes considering formability and spring-back. The effects of the material property, including strain-rate sensitivity on formability as well as spring-back were also evaluated numerically. As for the constitutive law, the isotropic hardening law was used along with the non-quadratic anisotropic yield function, Yld2000-2d. Forming limit diagrams were calculated based on Hill’s bifurcation theory and the MK theory. In order to characterize the material properties, tensile tests were performed for both the DP590 sheet and tube.
윤인준,류한선,고태조,김희술 한국공작기계학회 2004 한국생산제조학회지 Vol.13 No.3
Thermally induced errors of machine tools have been recognized as one of the most important issues in precision machining. This is probably the most formidable obstacle to obtain high level of machining accuracy. To this regard, the experimental compensation methodologies such as software-based method or origin shift of machine tool axes have keen suggested In this research, to cope with thermal deformation, a model based correction was carried out with the function of an external machine coordinate shift Models with multi-linear regression or neural network were investigated to selected a good one for thermal compensation. Consequently, multi-linear regression model combined with origin shift was verified good enough form the machining of dot matrices of plate with bail end milling.
시간 의존성 구성방정식을 이용한 AA6022-T4판재의 탄성 복원 예측
박태준(T. Park),류한선(R. Ryou),이명규(M. G. Lee),정경환(K. H. Chung),R.H. Wagoner,정관수(K. Chung) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
The time-dependent constitutive law was developed based on viscoelastic-plasticity to describe the time-dependent spring-back behavior of aluminum alloy 6022-T4 sheets. Besides nonlinear viscoelasticity, non-quadratic anisotropic yield function, Yld2000-2d, was used to account for the anisotropic yield behavior, while the combined isotropic-kinematic hardening law was used to represent the Bauschinger effect and transient hardening. For verification purposes, finite element simulations were performed for the draw-bending and the results were compared with experimental results.
소아 기관지천식 환자에서 혈액과 타액중의 Theophylline농도의 연관성에 관한 연구
오신근,권순한,윤운기,류한선,손기호,Charles D.Sands 대한천식알레르기학회 1993 천식 및 알레르기 Vol.13 No.1
Theophylline is widely used in Korean Pediatric patients in the treatment of asthma and neonatal apnea. To achieve adequate bronchodilation and avoid side effects, It is generally accepted that the serum theophylline concentration should be maintained between 10 and 20 mcg/ml. The measurement of this serum concentration usually requires a 3-5cc blood sample which on many occasions is repeated several times. In the pediatric population, especially, this exposes the children to multiple venipuncture with its potential associated trauma. To evaluate the reliability of salivary theophylline levels as a guide to serum theophylline levels, we studied the twenty of asthmatic children, who were admitted to our hospital and received intravenous aminophylline and oral sustained release theophylline. The mean theophylline concentration of Group I were 10.11+- 4.89mcg/ml in serum and 6.09+- 3.24mcg/ml in saliva. A strong correlation between the serum and saliva theophvlline levels, r=0.87, was noted and it is statistically significant. Regression Equation was se- rum conc. = 1.3050 X saliva conc. 2.1624. Also there was a good correlation between the predicted and actual theophylline concen trations, r=0.78, and no significant diR'erence between two values in Group II. These suggest that the determination of salivary theophylline concentration may be a convenient, noninvasive method for routine monitoring of serum theophylline concentration.