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This paper discusses mechanical digital servo press control system and operating characteristics and adaptability to the hot forming requirements of high strength steel using the toggle mechanical presses [1-4]. A servo motor drive control strategy is made to adapt the stamping process. This paper describes results acquired by applying toggle mechanical servo press developed by author to the hot forming of high strength steel [5-7].

Further research of the sheet metal single-point incremental forming (SPIF), which is a flexible sheet metal numerical forming method without dedicated dies, has used finite element method (FEM) simulation to analyse the forming principle and the effect of process parameters on the forming. In SPIF, the located region of the blank in contact with the forming tool is formed incrementally along the trajectory. There is no symmetric load and geometry condition, so the FEM model could not be simplified to a symmetrical model and the efficiency of simulation is bad. In this paper, brick elements are used to establish the whole three-dimensional FEM model and a simplified three-dimensional FEM model of a truncated cone and truncated pyramid. Comparison of the simulation results from the two models indicates that both models fit the simulation of SPIF but the simplified model is more efficient. Therefore, based on the simplified FEM model of a truncated pyramid, the SPIF process with different parameters was simulated to study the incremental forming principle. It was found that the deformed blank could be divided into three regions with different deformation patterns and the main character of the deformation could be conceded as a combination of bending and stretching.

To make the structure of aircraft meet the aerodynamic requirements, complex lightweight structures such as double curvature shape and high-strength lightweight materials such as titanium alloy are generally used in design and forming of aircraft skin parts. But the forming processes and problems aimed to this kind of parts remain to be investigated further now. In this paper, based on single point incremental forming process, the TC4 titanium alloy aircraft parts with a complex double curvature was studied. In order to reduce the springback during the forming process an appropriate addendum surface was added to the part surface, and then ABAQUS software was applied to carry out numerical simulation of the forming and springback process. The results show that springback of complex titanium part with double curvature is small at both ends of part while large in the middle and the distribution of springback orientation depends on the curvature. For that the part is difficult to form by single point incremental forming process without springback compensation, so the tool path needs to be improved firstly. The simulation results can play a role for guiding the parameters selection and the compensated surface design of single point incremental forming process which can achieve the cold forming of parts with complex structure for poor formability materials.

The solidification structure of Ti-6Al-4V round ingot during the electron beam cold hearth melting (EBCHM) directly determines the quality of the ingot and the performance of the subsequent rolled coil. In this paper, the Cellular Automaton Finite Element (CAFE) method is used to numerically simulate the solidification structure of Ti-6Al-4V ingot. Firstly, the mathematical model is established with a numerical solution. Secondly, effects of process parameters including the pouring temperature and pulling speed on the solidification structure are revealed. The results show that the microstructures predicted by the numerical method match the experimental results. For the case of fixed pulling speed, a reduction in the pouring temperature leads to the grain refinement and the decreased volatilization of Al. With an increase of the pulling speed, the number of grains first increases and then decreases, but the average grain size first decreases and then increases. Furthermore, the maximum grain size monotonically increases with increasing the pulling speed. Thus, the fine solidified structure with fine grains can be obtained at the pouring temperature of 1700 °C and the pulling speed of 4 × 10−4 m s−1.