Failure criterion for SPIF based on mean stress

In this paper, an analytical method was created to estimate single point incremental forming (SPIF)’s strain limits, based on mean stress calculated using membrane analysis. We conducted 27 formability experiments using different materials (SAE1008, AA1200-H14 and C268), different thicknesses and different tool radii values, followed by simulations of the finite element method (FEM) and analysis of variance (ANOVA). To validate the results obtained in these experiments, three FEM simulations were made. After the formability experiments, we were able to verify what effects the materials, the tool radii and the interaction between the two had on the stress value used as a failure criterion. The FEM simulations allowed us to validate analytical equations according to membrane equilibrium conditions, and the analytical method that considers the mean stress as critical stress presented good accuracy, with a maximum percentage error of 6.7%, compared to strain experimental values.