Chunxing Gu

Research on the Micro Sheet Stamping Process Using Plasticine as Soft Punch

Plasticine is widely used in the analysis of metal forming processes, due to its excellent material flow ability. In this study, plasticine is used as the soft punch to fabricate array micro-channels on metal sheet in the micro sheet stamping process. This is because plasticine can produce a large material flow after being subjected to force and through the material flow, the plasticine can cause the sheet to fill into the micro-channels of the rigid die, leading to the generation of micro-channels in the sheet. The distribution of array micro-channels was investigated as well as the influence of load forces on the sheet deformations. It was found that the depth of micro-channels increases as the load force increases. When the load force reaches a certain level, a crack can be observed. The micro sheet stamping process was also investigated by the method of numerical simulation. The obtained experimental and numerical results for the stamping process showed that they were in good agreement. Additionally, from the simulation results, it can be seen that the corner region of the micro-channel-shape work piece has a risk to crack due to the existence of maximum von Mises stress and significant thinning.

Experiment and numerical simulation of laser shock micro dents

In order to overcome the deficiencies of the traditional laser surface texturing, a useful surface texturing method by generating micro dents based on the laser shock processing technology was investigated in this paper. A series of experiments focusing on the effects of pulse energies and shock numbers for laser shock micro dents were carried out. An analysis procedure including dynamic analysis performed by ANSYS/LS-DYNA and static analysis performed by ANSYS is presented in detail to establish a 3D finite element model. By establishing more reasonable and accurate model, the simulation results would have better correlation with the experimental results. The bulges around the dents are observed in the experiment and simulation results. Besides, the calculation formula of laser shock wave pressure can be revised by comparing simulation results with experimental results.

Formation of nanostructure and nano-hardness characterization on the meso-scale workpiece by a novel laser indirect shock forming method

The meso-scale workpiece with greatly enhanced mechanical properties is potential to be widely used in the electronics productions and micro-electro mechanical systems. In this study, it demonstrates that the meso-scale cup-shape workpiece with good geometry can be obtained by a novel laser indirect shock forming method. After the forming process, the mechanical properties and microstructures of the formed workpiece were characterized. By transmission electron microscope observation, it was found that a mixed refined microstructure consisting of nano-scale twins embedded in nano-sized grains was produced at the center of the formed sample. Formation of these nanograins could be mainly attributed to two mechanisms: twin-twin intersections and twin∕matrix lamellae fragmentation. By nanoindentation tests, it reveals that the hardness of the sample has increased greatly after laser shock forming and the hardness increases with the laser energy. The elevated hardness originates from a considerable number of nano-scale twins and nanograins, which possess a pretty high strength due to the significant effects of grain boundary strengthening and twin boundary strengthening.