Formability of AA3003 brazing sheet at elevated temperatures: limiting dome height experiments and determination of forming limit diagrams

Warm forming has some important advantages, the most significant being that forming limit strains increase at elevated temperatures. To quantify this advantage for an AA3003 brazing sheet, forming limit diagrams were determined using warm tooling developed to perform limiting dome height (LDH) experiments together with a digital image correlation (DIC) system used to perform in situ strain measurement. Forming limit curves (FLCs) were developed at several temperature levels and strain-rates. The formability experiments demonstrated that while temperature has a significant effect on formability, forming speed has a mild effect within the studied range. Elevating the temperature to 250 degrees C improved the formability more than 200% compared to room temperature forming while forming at lower speeds increased the limiting strains by 10% and 17% at room temperature and 250 degrees C, respectively. A comparison between FLDs developed using DIC methods versus circle grid (CG) analysis showed good agreement between the two methods; however, the degree of scatter in the CG method increased significantly for the higher temperature tests.