Theory of single point incremental forming of tubes

Knowledge of the deformation mechanics in single point incremental forming of tubes is of great importance to understand the physics behind failure and the workability limits in thin-walled tube expansion. Which are the states of stress and strain in the small localized plastic deformation region between the tube and the single point forming tool, and how damage accumulates until fracture are important questions that this paper seeks to address by means of an analytical model based on membrane analysis. Comparisons are made against conventional tube expansion with a rigid punch to explore the main differences between the two processes regarding the states of stress and strain, the accumulation of damage and the likely mode of failure. The investigation is supported by experimentation performed in aluminium AA6063-T6 and shows that differences in deformation mechanics allow incremental tube expansion to withstand slightly higher values of damage before cracking than conventional tube expansion.