An experimental and numerical study of micro deep drawing of SUS304 circular cups

Abstract

-Micro deep drawing is a promising technology for mass production of complex 3D micro metal products. Significant size effects at a micro scale, however, obstruct application of this technology and block utilisation of traditional finite element method (FEM). Therefore, a micro tensile test system was developed to obtain accurate material properties considering size effects. Subsequently, a Voronoi blank model was developed for the micro scale simulation. Moreover, micro deep drawing experiments were conducted and their results were compared with the simulation results. The simulation results have a good agreement with the experimental data. Furthermore, the wrinkling at the cup mouth increases with the growth of grain sizes on the SUS304 sheets.

A study of the formability of stainless steel foils during micro deep drawing

“…figure 3(a) shows that the grains are gradually broken up, and the grain boundaries become blurred at the annealing temperature of 750 ℃. Meanwhile, recrystallized grains appear and gradually grow up by consuming the heavily deformed region around them [14]. When the temperature is increased to 950 ℃ (figure 3(b)), the microstructure is dominated by recrystallized grains with clear grain boundaries, indicating that recrystallization process has completed at this temperature [15].…”

Study of micro flexible rolling based on grained inhomogeneity

“…With respect to the finite element modelling for materials with size effect, Voronoi tessellation is a prevailing technique exploited to construct a polycrystalline microstructure comprising grains that have different properties equipped with them. Cao et al [32,33], Jiang et al [34] and Luo et al [35,36] produced numerical studies on the micro extrusion, micro hydroforming, micro cross wedge rolling, micro deep drawing and micro hydro deep drawing processes of polycrystalline materials generated by the Voronoi algorithm, respectively; all these results showcased that the mechanical properties and formability of the materials as well as the final product quality had strong affiliations with the properties of individual grains such as its size, morphology and orientation. In the wake of the uneven distribution of heterogeneous grains within these materials, the scatter effect of their general flow curves has been recognised and modelled with a normal bell-shaped distribution [37].…”

“…Additionally, in most cases of metal forming, the products are unlikely to be manufactured exactly to the specifications like size, shape, etc., as the deformed regions are prone to a certain amount of elastic recovery after release of the loading. Material behaviour of this type is termed springback, e.g., a slight decrease in the bending angle after the V-bending process, a slight increase in the flange angle after the deep drawing process, etc., which are affected by the factors such as process parameters, material properties and tooling geometries and have a chance of being compensated by overbending the material [29,35,[42][43][44][45]. Whilst for the strip rolling process springback may refer to the elastic recovery in the thickness after the strip exits the roll bite, and it is likely to be rectified by dint of increasing the rolling speed, adding tensions to the strip, decreasing the roll gap for a supplementary amount of reduction, and so forth [46][47][48][49][50].…”

Application of Finite Element Analysis in Multiscale Metal Forming Process

“…As shown in Figure 26b, the information of grains and individual closed subareas, including single grain's area, geometrical center and geometrical orientation, was detected and sorted in MATLAB. The blue ports in Figure 26b are the grain's geometrical centers [9,20,21]. After annealed at 1100°C, the 50 μm thick blanks, with equiaxed crystals microstructure and average grain size of 40 μm, were drawn into micro cups.…”

“…Open and closed lubricate pocket (OCLP) theory and size-dependent friction coefficient are proposed in micro deep drawing (MDD) and micro hydromechanical deep drawing (MHDD) [17][18][19]. Real microstructures and Voronoi structures are applied in microstructural models through the image-based modeling method [20,21].…”