ABSTRACT

In this study, hat-shaped bending experiments have been conducted on MART1200 and MART1400 Ultra-High-Strength Steels (UHSS). To investigate the influence of different lubrication conditions, on the spring-back, three different lubricant types (Graphite, Teflon film and Teflon film + Graphite) have been used in the experiments. A constant 6.5 tons of bottoming force has been applied at the end of the bending stroke and the force has been held on the samples for 0, 10s and 60s to observe the effect of force holding time on the spring-back. In addition, the effect of blankholder force on the spring-back has also been investigated for MART1400 steel. It has been found that the decrease of blankholder force and the friction between the die and sheet interfaces has considerably reduced the spring-back in the sidewalls and flange regions and also lowered the side wall curl. It has been revealed through finite element analysis that the sheet bottom has suffered a larger deformation in lower friction conditions and blankholder forces and caused in the reduction of spring-back.

摘要

在本研究中，对 MART1200 和 MART1400 超高强度钢 (UHSS) 进行了帽形弯曲实验。为了研究不同润滑条件对回弹的影响，实验中使用了三种不同的润滑剂类型（石墨、聚四氟乙烯薄膜和聚四氟乙烯薄膜+石墨）。在弯曲行程结束时施加恒定的 6.5 吨触底力，并在样品上保持力 0、10 秒和 60 秒，以观察力保持时间对回弹的影响。此外，还研究了 MART1400 钢的压边力对回弹的影响。已经发现，压边力以及模具和板材界面之间的摩擦的减小显着地减少了侧壁和凸缘区域中的回弹并且还降低了侧壁卷曲。通过有限元分析发现，在较低摩擦条件和压边力的情况下，板料底部发生较大变形，导致回弹减少。