Prandtl-Reuss flow rule and Hill’s yield criterion were adopted and combined with the concept of finite deformation theory, updated Lagrangian formulation, and a three-dimensional finite element analytical model was ...Prandtl-Reuss flow rule and Hill’s yield criterion were adopted and combined with the concept of finite deformation theory, updated Lagrangian formulation, and a three-dimensional finite element analytical model was established by application of quadrilateral four-node degenerated shell elements coupling into a rigid matrix to deal with the sheet metal forming problems. The fractured thickness of a specimen obtained from a simple tension test was used to be the fracture criterion for the numerical analysis to explore the relationship between punch load and stroke, the thickness distribution, the deformation history and the forming limit of work-piece in the elliptical cup drawing process. The numerical analysis and experiment results show that the punch load increases with the increase of punch stroke, and when the load reaches its maximum, the blank continues to deform with the increase of the punch stroke, resulting in a reduced load until the extension is completed. The minimum thickness of the work-piece concentrates in the contact region of the work-piece and long axis of the punch due to the smaller radius of the curvature of the long axis than the short axis. So the blanks bore the maximum tensile stress in the long axis. Through the limit drawing ratio defined by perimeter of the elliptical punch, the limit drawing ratio of this elliptical cup drawing is defined to be 2.136.展开更多
The liner of a CNG pressure vessel is manufactured by a DDI(deep drawing and ironing)process for the cylinder part,which is a continuous process that includes a drawing process to reduce the diameter of the billet and...The liner of a CNG pressure vessel is manufactured by a DDI(deep drawing and ironing)process for the cylinder part,which is a continuous process that includes a drawing process to reduce the diameter of the billet and a subsequent ironing process to reduce the thickness of the billet.A tractrix die used in the 1^(st) deep drawing allows the blank to flow smoothly by decreasing the punch load and radial tensile stress occurring in the workpiece.It also increases the draw ratio compared to conventional dies,but it causes forming defects.In this study,a shape coefficient(S_(c))is proposed for the tractrix die using the blank diameter(D_(0)),inflow diameter of the workpiece(d_(i)),and inflow angle of the workpiece(θ)for design of the tractrix die.The effects of the thickness and inflow angle of the workpiece on wrinkling and folding were investigated through FEA.Also,a discriminant is proposed for the relative radial stress(σ)generated during the deep drawing process using the tractirx die and used to predict fracture.Based on the results,the blank thickness,the draw ratio,and the inflow of the workpiece angle in the 1^(st) deep drawing process are suggested,and the number of operations in the DDI process was reduced from 6 to 4.This improves the productivity and reduces the manufacturing cost.展开更多
To investigate how the popular magnesium alloy AZ31 sheet(aluminum 3%,zinc 1%)behaves in cold working,deep drawing experiments at room temperature,along with finite element(FE)simulation,were performed on the cold for...To investigate how the popular magnesium alloy AZ31 sheet(aluminum 3%,zinc 1%)behaves in cold working,deep drawing experiments at room temperature,along with finite element(FE)simulation,were performed on the cold forming sheet of the AZ31 alloy after being annealed under various conditions.The activities were focused on the fracture pattern,limit drawing ratio(LDR),deformation load,thickness distribution,anisotropic effect,as well as the influences of the annealing conditions and tool configuration on them.The results display that punch shoulder radius instead of die clearance,has much influence on the thickness distribution.The anisotropy is remarkable in cold working,which adversely impacts the LDR.The fracture often happens on the side wall at an angle to axis of the deformed specimen.The results also imply that the LDR for the material under present experimental conditions is 1.72,and annealing the material at 450 ℃ for 1 h may be preferable for the cold deep drawing.展开更多
基金funded by research projects (NSC97-2221-E-129-003) of the National Science Council
文摘Prandtl-Reuss flow rule and Hill’s yield criterion were adopted and combined with the concept of finite deformation theory, updated Lagrangian formulation, and a three-dimensional finite element analytical model was established by application of quadrilateral four-node degenerated shell elements coupling into a rigid matrix to deal with the sheet metal forming problems. The fractured thickness of a specimen obtained from a simple tension test was used to be the fracture criterion for the numerical analysis to explore the relationship between punch load and stroke, the thickness distribution, the deformation history and the forming limit of work-piece in the elliptical cup drawing process. The numerical analysis and experiment results show that the punch load increases with the increase of punch stroke, and when the load reaches its maximum, the blank continues to deform with the increase of the punch stroke, resulting in a reduced load until the extension is completed. The minimum thickness of the work-piece concentrates in the contact region of the work-piece and long axis of the punch due to the smaller radius of the curvature of the long axis than the short axis. So the blanks bore the maximum tensile stress in the long axis. Through the limit drawing ratio defined by perimeter of the elliptical punch, the limit drawing ratio of this elliptical cup drawing is defined to be 2.136.
基金Supported by a 2-Year Research Grant of Pusan National University,Korea。
文摘The liner of a CNG pressure vessel is manufactured by a DDI(deep drawing and ironing)process for the cylinder part,which is a continuous process that includes a drawing process to reduce the diameter of the billet and a subsequent ironing process to reduce the thickness of the billet.A tractrix die used in the 1^(st) deep drawing allows the blank to flow smoothly by decreasing the punch load and radial tensile stress occurring in the workpiece.It also increases the draw ratio compared to conventional dies,but it causes forming defects.In this study,a shape coefficient(S_(c))is proposed for the tractrix die using the blank diameter(D_(0)),inflow diameter of the workpiece(d_(i)),and inflow angle of the workpiece(θ)for design of the tractrix die.The effects of the thickness and inflow angle of the workpiece on wrinkling and folding were investigated through FEA.Also,a discriminant is proposed for the relative radial stress(σ)generated during the deep drawing process using the tractirx die and used to predict fracture.Based on the results,the blank thickness,the draw ratio,and the inflow of the workpiece angle in the 1^(st) deep drawing process are suggested,and the number of operations in the DDI process was reduced from 6 to 4.This improves the productivity and reduces the manufacturing cost.
文摘To investigate how the popular magnesium alloy AZ31 sheet(aluminum 3%,zinc 1%)behaves in cold working,deep drawing experiments at room temperature,along with finite element(FE)simulation,were performed on the cold forming sheet of the AZ31 alloy after being annealed under various conditions.The activities were focused on the fracture pattern,limit drawing ratio(LDR),deformation load,thickness distribution,anisotropic effect,as well as the influences of the annealing conditions and tool configuration on them.The results display that punch shoulder radius instead of die clearance,has much influence on the thickness distribution.The anisotropy is remarkable in cold working,which adversely impacts the LDR.The fracture often happens on the side wall at an angle to axis of the deformed specimen.The results also imply that the LDR for the material under present experimental conditions is 1.72,and annealing the material at 450 ℃ for 1 h may be preferable for the cold deep drawing.
