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용탕단조법에 의하여 제조한 $SiC_p$/Al 복합재료의 2차 성형공정이 기계적 성질에 미치는 영향
서영호,강충길,Seo, Y.H,Kang, C.G 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.11
A metal matrix composites(MMCs) for A16061 reinforced with silicon carbide particles is fabricated by melt-stirring method. The primary products of MMCs billets are prepared by volume fractions 5 vol% to 20 vol% and particle size $13\mu m$ to $22\mu m$.This paper will be made to examine the microstructure and mechanical properties of fabricated $SiC_p$/Al 6061 composite by melt-stirring and squeeze casting method. The MMC billets is extruded at $500^{\circ}C$ under the constant extrusion velocity $V_e$=2mm/min using curved shape die. Extrusion force, particle rearrangement, micro structure and mechanical properties of extruded composites will be investigated. The mechanical properties of primary billets manufactured by melt-stirring and squeeze casting method will be compared with extrusion specimen. The effect of volume fraction and size of the reinforcements will be studied. The increase in uniformity of particle dispersion is the major reason for an improvement in reliability due to hot extrusion with optimal shape die. Experimental Young's modulus and 0.2% offset yield strength for the extruded MMCs will be compared with theretical values calculated by the Eshelby method. A method will be proposed for the prediction of Young's modulus and yield strength in $SiC_p$ reinforced MMCs.
유한요소법을 이용한 가변스테레치성형 공정변수와 성형오차의 상관관계 연구
서영호(Y. H. Seo),허성찬(S. C. Heo),강범수(B. S. Kang),김정(J. Kim) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
In this study, a correlation analysis between a process variable and shape error in a flexible stretch forming is conducted using finite element method. The forming variables which affect to the shape error are punch size, objective curvature radius and elastic pad thickness. Numerical simulations for calculating of the shape error are carried out by factorial design. The shape error is calculated and the correlation analysis is also performed according to width and tensile directions. Consequently, the correlation coefficient is deducted and it describes that the shape error is in proportional to the punch size and is in inverse to the objective curvature radius and the elastic pad thickness.
성형 오차 예측 모델을 이용한 가변 성형 공정에서의 탄성 회복 보정
서영호(Y. H. Seo),강범수(B. S. Kang),김정(J. Kim) 한국소성·가공학회 2012 소성가공 : 한국소성가공학회지 Vol.21 No.8
The objective of this study is to compensate the elastic recovery in the flexible forming process using the predictive models. The target shape was limited to two-dimensional shape having only one curvature radius in the longitudinaldirection. In order to predict the shape error the regression and neural network models were established based on the finite element (FE) simulations. A series of simulations were conducted considering input variables such as the elastic pad thickness, the thickness of plate, and the objective curvature radius. Then, at sampling points in the longitudinal-direction, the shape errors between formed and objective shapes could be calculated from the FE simulations as an output variable. These shape errors were expressed to a representative error value by the root mean square error (RMSE). To obtain the correct objective shape the die shape was adjusted by the closed-loop using the neural network model since the neural network model shows a higher capability of estimating the shape error than the regression model. Finally the experimental result shows that the formed shape almost agreed with the objective shape.