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As one of the principal failures that occur in metal spin-forming and tube-bending processes, ductile fracturing restricts the process of metal forming. It is difficult to predict the rupture and forming limit for the complex processes of spin forming and tube bending. Thus, in this paper we aim to choose reasonable ductile fracture criteria to accurately predict the time, position and distribution of the damage that occurs in these processes. By embedding the Lemaitre and Cockcroft–Latham (C&L) criteria into VUMAT (user material subroutine of the ABAQUS/explicit finite element method (FEM) code), finite element models are built and validated for predicting rupture failure and forming limit in the shear spin-forming, splitting spin-forming and tube-bending processes. The results show that the Lemaitre criterion is better than the C&L criterion at accurately predicting the position at which damage will occur and its distribution for both spin forming and tube bending. The maximum feed ratio varies within a small range with the splitting angle of the roller. There is an obvious difference between the distribution, variation and level of the damage that can occur for a normal bending radius without rupturing, and that for a very small bending radius, where there is a greater risk of rupturing. For tube bending using a very small bending radius and without a mandrel in the tube, the pressure die velocity increases, so the flattening of the bending area increases to some extent, which makes it opposite of normal tube bending.

The forming characteristics of splitting spinning based on the behaviors of roller is one important key of improvement of materials forming limit and forming precision. In this paper, the relationship between continuous feed conditions and feed amount of roller is obtained by the static analysis of splitting spinning. Based on the numerical relationship, the forming characteristics of splitting spinning based on the behaviors of roller is studied, including geometric parameter, boundary condition and contact. According to the above analysis of forming characteristics, a 3D elastic–plastic FE model of splitting spinning is established using the dynamic explicit FE code ABAQUS/Explicit, and then the reliability is proved by comparisons with experimental data. Furthermore, the influence laws of forming parameters of splitting spinning on the quality and precision of flanges are investigated under different forming conditions. The results are as follows: (1) On the conditions of 20 ⩽ α ⩽ 45° and r 0 = 1.5 mm, deformed flanges satisfy high quality and high precision. (2) When feed rate 1.0 v ω ⩽ 70 round/min, both the angle deviation of inner-face/outer-face goes towards zero. (3) The variation of friction coefficients between contact surfaces influencing on the degree of inhomogeneous deformation and thickness deviation of deformed flanges is notable, and influencing on the angle deviation is steady and even enough to obtain high quality and high precision. The forming characteristics of splitting spinning based on the behaviors of roller are revealed, and meanwhile the relative slip between roller and the workpiece and the non-uniform rotation and reverse rotation of roller may be avoided. The results may help to better understand the forming characteristics of splitting spinning based on the behaviors of roller and improve materials forming limit and forming quality.

B3PW91/6-31G density functional method was employed to investigate the elastic, strength and electronic properties of C 60 ( I h ) in its ground electronic state (X 1 A g ). Most of the properties were examined for larger structure distortions. The over-all elastic constant were derived from the near-equilibrium potential energy curves (PECs) in five independent directions [according to symmetries by 1. D 5d , 2. D 3d , 3. D 2h , 4. C 2h (1), 5. C 2h (2)]. By extension of the distortions as large as the structure of C 60 was destroyed, the necessary energies were obtained, which quantitatively illuminated the stability of C 60 theoretically. Analytical polynomial fit of the full PECs reproduced the energy data accurately. Time-dependent B3PW91/6-31G analysis showed significant electronic spectra changes associated with the structure distortions. Elongation in the direction of D 5d and compression in that of D 2h encountered potential energy surface cross-linkages, which might be considered as a single electron pump for further application in designs of single electron devices.