Grain Size Effect in the Micro-V-Bending Process of Thin Metal Sheets

The aim of this study is to develop a micro-V-bending testing system and to investigate the grain size effect of 99.5% Ferrum sheet plate in the micro-V-bending process. In this study, two experiments have been conducted. They attempt to explain the characteristic of thickness variation at a constant average grain size of 29.93 mu m with a standard deviation (SD) of 2.4 and the different average grain sizes at a constant mean thickness of 490.63 mu m with a SD of 11.3. A laser displacement sensor is employed to monitor the real position of punch movement and to verify the effective stroke. In the micro-V-bending test, the thickness/average grain size (T/D) ratio is used to discuss material behavior such as punch force, springback, and spring-forward. According to the results, the conventional concept of V-bending deformation cannot be applied to different average grain sizes at a constant thickness in the micro-V-bending test particularly when the T/D ratio is less than 2.