Effect of thickness and grain size on material behavior in micro-bending

Micro-bending tests were performed to investigate effects of thickness and grain size on material behavior in sheet metal forming. The rolling brass C2680 foil was selected as the experimental material, and it was annealed to eliminate the work-hardening and get different grain sizes. A device was specially designed for three-point bending with two load sensors. The results show that the bending force increases with increasing the punch displacement. With the foil of same thickness, a smaller punch radius leads to a larger bending force. When the grain size increases, the bending force becomes smaller. Size effects are observed obviously. These results have been analyzed by work-hardening, Hall-Petch equation and free surface effect.