Size effect affected deformation characteristics in micro deep drawing of TWIP domed-bottom cups

Abstract

The occurrence of size effect in micro-scale deep drawing leads to the geometrical uncertainties, which affects the deformation behavior, in process determination. Micro deep drawing of domed-bottom cups of Fe-30Mn-3Si-2Al-0.11C TWIP steel with different grain size and thickness size was investigated in this research to obtain the characteristics of micro-deformed sheet to study the size effect on deformation behavior, earing profile and defect formation of the micro-parts. Finite element simulation shows fracture in the place with the thinnest thickness of the micro-parts easily occurs around the punch corner. Deformation load decreases with the increasing grain size for each thickness size except the fracture case, while under the particular grain size the load increases with the increase of thickness. Earing easily occurs with the larger grain size and smaller thickness size in the well-formed domed-bottom cups. Inhomogeneous deformation leads to irregular geometry of the formed part. The research promotes the understanding of size effect on micro deep drawing and facilitates the development of micro forming process.