Papers by Author: Qi Gang Han

Abstract: Large volume cubic anvil (LVCA) have been widely used in cubic high pressure apparatus, which can accommodate a large sample volume (the largest volume of compressed cell is 422 cm3), but they are limited by shorter lifetime (£143000 times) and lower cell pressure (£146 GPa). In this paper, we have designed of a double radius type LVCA, which has three advantages. Firstly, the rate of cell pressure transmitting and the pressurized seal stability of the sample cell can be maintained, which is often sacrificed with optimum the geometrical condition of the anvil. Secondly, the lifetime of double radius type LVCA can be increased about 19.86 % than that of traditional anvil. Thirdly, the cell pressure can be increase about 13.45 % after the modification of the anvil. This work makes an effective solution for solve the choke points of LVCA and would be used widely in other types of Multi-anvil apparatuses.

Abstract: Stretch forming machine (SFM) is most effective plastic forming equipment for large-size, thin and flat-deformation parts, which can decrease the springback phenomenon in sheet metal forming. In order to enhance the performance of SFM, a flexible stretch forming machine (FSFM) was developed by the authors successfully, which is made up of jaw clamping mechanisms, stretching mechanisms, universal push-pull mechanisms, and a carriage. Our experimental results indicated that the rate of materials utilization and close-fitting dies can be increased to 80 %. In addition, FSFM can reduce the complex of control-system and decrease the expense of machine sharply. FSFM have been used for double-curved sheet metal manufacturing successfully, such as the cab of high-speed train. This work has a strong value in enhance the stretch forming technology for double-curved sheet metal parts.

Abstract: Multi-point holder forming (MPHF) adopts series of coupled holder punches, arranged between forming punches, to clamp the whole sheet in the forming zone. The multi-point holder forming processes of spherical parts of titanium mesh plate were simulated by finite element code, and the results were compared with those of multi-point die forming (MPDF). The influence of holder punch load on the deformation of spherical part in multi-point holder forming was investigated. The shape error analysis of titanium mesh formed by MPHF was performed in finial. The results showed that the spherical part had more excellent performance in multi-point holder forming, and the more deformation the titanium mesh was, the larger force of holder punch would be needed. In addition, there was a small shape error for titanium mesh part formed by MPHF before springback.

Abstract: In order to save the manufacturing cost and solve problems of stamping, a new type of flexible blank-drawer (FBD) forming device was presented by the authors based on the principle of flexible stretch-forming. It can be used with a variety of different sizes, different shapes of stamping die which can cut the manufacturing cost and shorten the development cycle of sheet metal forming largely. Extensive numerical simulations of the process for forming saddle parts were carried out and the forming results using FBD were compared with those using traditional blank-holder (TBH). By adjusting the value of blank-drawer force, good quality of saddle parts can be attained easily. Simulation results indicate that FBD forming can solve the shortages of TBH forming, inhibit wrinkle, prevent fracture, and form parts with small springback and uniform strain. This work can provide useful guidance in plastic forming technology for sheet metal.

Abstract: A new type of discrete clamp stretch forming machine based on flexible holding technology was developed to improve the performance of traditional rigid clamp stretch forming machine used for double-curvature metal sheet forming, and its forming characters were illuminated simply. The FE model of flexible discrete clamp stretch forming was set up, and extensive numerical simulations of spherical parts for both the flexible holding mode and the rigid holding mode were carried out by dynamic explicit finite element analysis. The numerical results show that the distribution of stress, strain and thickness were well-proportioned in the flexible holding mode. The larger the spherical radius is, the smaller the minimum transitional length of sheet metal is. The transitional length of 60mm is suitable for flexible discrete clamp stretch forming in the case of considering the forming quality and material utilization. Then, the stretch forming experiment proves that the flexible holding technology is feasible, and the error contrast illustrates the new type of discrete clamp stretch forming machine is practicable.

Abstract: In order to improve the performance of back drawing type of flexible multi-gripper stretch forming machine used for double-curvature metal sheet forming, back and down drawing type of flexible multi-gripper stretch forming machine was designed by finite element method (FEM), which has simple structure and cheap cost. The FE model of flexible multi-gripper stretch forming was established, and extensive numerical simulations of spherical parts for two kinds of flexible stretch forming machines were carried out. The variations of stress, strain, thickness and springback value of spherical parts for two kinds of drawing modes were analyzed. The numerical results show that the quality of spherical parts formed by the back and down drawing type of stretch forming machine is better than that by the back drawing type of stretch forming machine. This work provides a machine for developing the technology of stretch forming.