Determining the fracture forming limits in sheet metal forming: A technical note

This technical note describes an experimental method to determine the formability limits by fracture in sheet metal forming. The method makes use of laboratory test specimens commonly utilized in the mechanical, fracture and formability characterization of sheet materials and involves determination of the gauge length strains at the cracked regions of the specimens after testing. The presentation explains how measurements are made and what calculations need to be performed in order to determine the fracture forming limit by tension in the principal strain space. The method is applied to Titanium grade 1 sheets, and the fracture forming limit is validated by subsequent experiments with single point incremental forming.