Failure and strain gradient analyses in incremental forming using GTN model

Abstract Single point incremental forming (SPIF) process is gaining popularity for rapid manufacturing of complex 3D shapes. The present study is aimed at numerically predicting the failure using the Gurson-Tvergaard-Needleman (GTN) model and further clarifying the deformation mechanics in SPIF. Deformation mechanics and failure in SPIF process are examined numerically by simulating a straight groove test. Solid finite element (FE) models have been employed to investigate deformation modes. The GTN damage model has successfully predicted forming limits in the straight groove test. It is shown that failure, regardless of the incremental sheet forming (ISF) conditions, occurs when the damage parameter (d) approaches one. Furthermore, effective plastic strain, hydrostatic pressure, vertical tool force and through thickness strain gradient increase with an increase in step size. Finally, it is shown that an increase in hydrostatic pressure and increase in through thickness strain gradient enhance formability.