Size Effects in Micro-Forming

作者：Balint Daniel S^*; Wang Shiwen; Lin Jianguo

来源：Steel Research International, 2010, 81(9): 1229-1232.

• Micro-forming
• Size effects
• Crystal plasticity
• Hydro-forming
• Micro-tubes
• Necking
• Extrusion
• Hardening

Size effects arise in material deformation when the smallest specimen dimension is on the order of an intrinsic length scale in the material, e.g. grain size. Observations include classic grain size strengthening (Hall-Petch effect), as well as more recent observations of specimen size effects (torsion, tension) and the indentation size effect. Size effects also arise naturally in micro-forming, which in turn can lead to unanticipated irregularities in manufacturing. In this paper, an overview of size effects will be given followed by a set of crystal plasticity simulations of micro-forming applications (drawing of micro-wires/films, hydro-forming of micro-tubes, extrusion of micro-pins) where size effects arise. Based on the simulation results, ways of eliminating the observed manufacturing irregularities in these applications will be discussed. Further, a hardening relationship that incorporates the contributions of self and latent hardening into the crystal plasticity formulation, calibrated by discrete dislocation calculations, will be introduced.

• 出版日期2010-9