The influence of the size of pre-cut hole of blank on the formability of cylindrical hole flanging in single point incremental forming（SPIF） was studied. The flange is produced in four stages starting from 45° ...The influence of the size of pre-cut hole of blank on the formability of cylindrical hole flanging in single point incremental forming（SPIF） was studied. The flange is produced in four stages starting from 45° to 90° and employing aluminum as the test material. It is shown that the hole size has significant effects on the stress/strain distribution on the cylindrical flange. The magnitude of hoop strains increases and the flange thickness increases as the hole size increases. Likewise, the von Mises stress reduces with the increasing of hole size. Further, there is a threshold value of hole size（i.e., 80 mm） below which severe stresses occur, which lead to sheet fracturing thus failing the successful forming of cylindrical flange. Moreover, the formability reduces as the hole size is increased above the threshold size. Finally, it is concluded that 80 mm is the threshold size of hole for maximizing the formability of aluminum sheet in incremental hole flanging.展开更多
An incremental updated Lagrangian elasto-plastic finite element method(FEM) was employed to analyze the hole-flanging with the ironing of circulate plates using a pre-determined smaller hole at the center of the two-p...An incremental updated Lagrangian elasto-plastic finite element method(FEM) was employed to analyze the hole-flanging with the ironing of circulate plates using a pre-determined smaller hole at the center of the two-ply sheet metals. An extended rmin technique was employed such that each incremental step size can be determined not only by the yielding of an element Gaussian point, but also by the change under the boundary conditions of penetration, separation, and the alternation of the sliding-sticking state of friction along the tool-sheet interface. Two-ply sheet metals are generally composed of metals that have different mechanical properties. Thus, the forming process of these materials is complicated. A number of experiments and simulations were performed using a conical punch with a cone angle of 45°. The experimental results were compared with FEM-simulated results. It is found that using the elasto-plastic FEM can effectively predict the generation process of the deformed shape until unloading. The calculated sheet geometries and the relationship between punch load and punch travel are in good agreement with the experimental data.展开更多
The forming mechanism of hole flanging on a thick-wall heavy cylinder forging is simulated by DEFORM3D. The cylinder is 4 390 mm in diameter and 390 mm in thickness. The results show that the compound deformation with...The forming mechanism of hole flanging on a thick-wall heavy cylinder forging is simulated by DEFORM3D. The cylinder is 4 390 mm in diameter and 390 mm in thickness. The results show that the compound deformation with bending and expanding happens in the process of hole flanging. The diameter of pre-hole of the workpiece is one of the key parameters in the process of hole flanging. The optimal diameter is obtained for reverse-conical hole of average diameter 40 mm by simulation of hole flanging process on 5 pre-holes with different diameters and 3 pre-holes with different shapes. The results can provide the scientific base for engineering application of the process.展开更多
In this study, the effect of various factors on the hole expansion ratio and hence on the edge formability of two hot rolled multiphase steels, one with a ferrite–martensite microstructure and the other with a ferrit...In this study, the effect of various factors on the hole expansion ratio and hence on the edge formability of two hot rolled multiphase steels, one with a ferrite–martensite microstructure and the other with a ferrite-bainite microstructure, was investigated through systematic microstructural and mechanical characterization. The study revealed that the microstructure of the steels, which determines their strain hardening capacity and fracture resistance, is the principal factor controlling edge formability. The influence of other factors such as tensile strength, ductility, anisotropy, and thickness, though present, are secondary. A critical evaluation of the available empirical models for hole expansion ratio prediction is also presented.展开更多
文摘The influence of the size of pre-cut hole of blank on the formability of cylindrical hole flanging in single point incremental forming（SPIF） was studied. The flange is produced in four stages starting from 45° to 90° and employing aluminum as the test material. It is shown that the hole size has significant effects on the stress/strain distribution on the cylindrical flange. The magnitude of hoop strains increases and the flange thickness increases as the hole size increases. Likewise, the von Mises stress reduces with the increasing of hole size. Further, there is a threshold value of hole size（i.e., 80 mm） below which severe stresses occur, which lead to sheet fracturing thus failing the successful forming of cylindrical flange. Moreover, the formability reduces as the hole size is increased above the threshold size. Finally, it is concluded that 80 mm is the threshold size of hole for maximizing the formability of aluminum sheet in incremental hole flanging.
文摘An incremental updated Lagrangian elasto-plastic finite element method(FEM) was employed to analyze the hole-flanging with the ironing of circulate plates using a pre-determined smaller hole at the center of the two-ply sheet metals. An extended rmin technique was employed such that each incremental step size can be determined not only by the yielding of an element Gaussian point, but also by the change under the boundary conditions of penetration, separation, and the alternation of the sliding-sticking state of friction along the tool-sheet interface. Two-ply sheet metals are generally composed of metals that have different mechanical properties. Thus, the forming process of these materials is complicated. A number of experiments and simulations were performed using a conical punch with a cone angle of 45°. The experimental results were compared with FEM-simulated results. It is found that using the elasto-plastic FEM can effectively predict the generation process of the deformed shape until unloading. The calculated sheet geometries and the relationship between punch load and punch travel are in good agreement with the experimental data.
文摘The forming mechanism of hole flanging on a thick-wall heavy cylinder forging is simulated by DEFORM3D. The cylinder is 4 390 mm in diameter and 390 mm in thickness. The results show that the compound deformation with bending and expanding happens in the process of hole flanging. The diameter of pre-hole of the workpiece is one of the key parameters in the process of hole flanging. The optimal diameter is obtained for reverse-conical hole of average diameter 40 mm by simulation of hole flanging process on 5 pre-holes with different diameters and 3 pre-holes with different shapes. The results can provide the scientific base for engineering application of the process.
文摘In this study, the effect of various factors on the hole expansion ratio and hence on the edge formability of two hot rolled multiphase steels, one with a ferrite–martensite microstructure and the other with a ferrite-bainite microstructure, was investigated through systematic microstructural and mechanical characterization. The study revealed that the microstructure of the steels, which determines their strain hardening capacity and fracture resistance, is the principal factor controlling edge formability. The influence of other factors such as tensile strength, ductility, anisotropy, and thickness, though present, are secondary. A critical evaluation of the available empirical models for hole expansion ratio prediction is also presented.
