Liang Luo

Surface modification of titanium and its alloys for biomedical application

Titanium and its alloys have excellent properties and are promising biomaterial in medical engineering field. A bioactive surface on a Ti substrate is a prerequisite for great performance and long service life of implants. Based on the mechanism for inducing cell/tissue responses, three kinds of methods, namely morphological, physicochemical and biochemical methods, are reviewed in this paper. Hybrid methods that integrate individual methods or have additional functions are also discussed.

Study on micro hydroforming of metals

Micro hydroforming has an ability to manufacture complex 3D micro parts at a high production rate and has drawn increasing attentions. Brief understanding of macro hydroforming, for instance, deep drawing, is necessary to understand the principle of micro hydroforming. Then, special phenomena, such as size effects, occurred at micro scale are discussed and the related theories explaining these phenomena are introduced. Based on the similarities and differences between micro and macro hydroforming, experiments and simulation which consider the size effects are reviewed.

A Numerical Study of Micro Hydro Deep Drawing of SUS304 Sheets

Micro forming is a promising technology and has drawn global attentions due to the urgent requirements on miniaturised products. Micro hydro deep drawing (MHDD) is a typical micro forming method and its products are widely applied in various fields, such as micro electro-mechanical systems (MEMS), medical and aerospace areas. However, tiny sizes of both products and tools are obstacles to investigate this novel technology. Therefore, finite element method (FEM) is adopted and modified to study the influence of processing parameters on micro drawing process and produced products. In this study, a normal hydro deep drawing model was developed, and then a voronoi blank model was generated to consider the size effects of materials. Additionally, a surface layer model was created based on the voronoi blank model. Therefore, the open and closed lubricant theory can be fulfilled and friction behaviour in MHDD can be considered. Subsequently, different processing parameters, such as hydraulic pressure and material inhomogeneity, were investigated. Simulation results indicate that a proper hydraulic pressure improves drawability and shape accuracy of the drawn cups. Moreover, material inhomogeneity affects the quality of drawn cups.

Effects of hydraulic pressure on shape accuracy of drawn circular cups during micro hydro deep drawing

Micro hydro deep drawing is a promising technology to fabricate micro metal products with complex 3D shapes. However, the size effects in the micro hydro deep drawing become considerable and significantly influence shape accuracy of drawn cups. In this study, a Voronoi micro scale simulation model was developed to consider the size effects of SUS304 foils. A surface layer model was additionally applied in the simulation to further explain the size effects. The micro hydro deep drawing experiments were conducted with annealed SUS304 foils and the drawn cups were examined. The wrinkling phenomenon was generally aggravated with the hydraulic pressure. Simulation results also show that the high hydraulic pressure does not improve the shape accuracy of the drawn cups as that in the normal scale hydro deep dawning process does. The simulation results are in accordance with the experimental results.