Development of Micro V-bending System for Investigation Grain Size Effect of Thin Metal Sheet

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 understand the characteristic of thickness variation at a constant average grain size of 29.93 ¿ m with a standard deviation (SD) of 2.4 and different average grain sizes at a constant mean thickness of 490.63 ¿ 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. The T/D (thickness/average grain size) ratio is used to discuss material behavior such as punch force, spring-back and spring-forward in the micro V-bending test. 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; in particular, if the T/D ratio is less than 2.