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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.
GhorbaniMenghari, Hossein,Poor, Hamed Ziaei,Farzin, Mahmoud,Alves De Sousa, Ricardo J. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.4
In hydroforming, the general technique employed to overcome the problem of die corner filling consist in increasing the maximum fluid pressure during the forming process. This technique, in other hand, leads to other difficulties such as thinning and rupturing of the final work piece. In this paper, a new technique has been suggested in order to produce a part with complete filled corners. In this approach, two moveable bushes have been used. So, the workpiece moves driven by both bushes simultaneously. In the first stage, system pressure increases until a maximum of 15 MPa, providing aninitial tube bulge. The results showed that the pressure in this stage have to be limited to 17 MPa to avoid fracture. In a second stage, bushes are moved keeping the constant initial pressure. The punches act simultaneously at the die extremities. Results show that the friction between part and die decreases during the forming process significantly. Also, by using this technique it is possible to produce a part with reasonable uniform thickness distribution. Other outcomes of applying this method are the lower pressures required to manufacture a workpiece with complete filled corners with no wrinkling.
Hossein GhorbaniMenghari,Hamed Ziaei Poor,Mahmoud Farzin,Ricardo J. Alves De Sousa 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.4
In hydroforming, the general technique employed to overcome the problem of die corner filling consist in increasing the maximum fluid pressure during the forming process. This technique, in other hand, leads to other difficulties such as thinning and rupturing of the final work piece. In this paper, a new technique has been suggested in order to produce a part with complete filled corners. In this approach, two moveable bushes have been used. So, the workpiece moves driven by both bushes simultaneously. In the first stage, system pressure increases until a maximum of 15 MPa, providing aninitial tube bulge. The results showed that the pressure in this stage have to be limited to 17 MPa to avoid fracture. In a second stage, bushes are moved keeping the constant initial pressure. The punches act simultaneously at the die extremities. Results show that the friction between part and die decreases during the forming process significantly. Also, by using this technique it is possible to produce a part with reasonable uniform thickness distribution. Other outcomes of applying this method are the lower pressures required to manufacture a workpiece with complete filled corners with no wrinkling.