Tensile testing over time is the first step in determining property variation for new material forming. However, industrial stamping processes often experience higher strain than what can be measured in a tensile test. Bulge testing can dramatically improve the accuracy of the yield surface of new materials.
The EWI Forming Center recently developed the bulge test capability to obtain flow stress of sheet metals to the highest strain level before necking. This differs from conventional bulge testing by adopting Digital Image Correlation (DIC) cameras to accurately determine bulging height and curvature profile for strain calculation. You can learn about it in The Bulge Test: A Valuable Tool for Material Formability Evaluation. Written by EWI associates J. Clare Gu and Huynok Kim, this paper discusses EWI’s research using DIC to improve bulge testing.