Failure behavior in single point incremental forming parts of AA6061-T6

Single point incremental forming (SPIF) forms 3D components using a hemispherical tool without needing a component-specific die/punch. Although SPIF is proven to enhance material formability, the successful forming of high-strength materials is difficult due to their lower ductility. The current work presents a comprehensive failure analysis of SPIF components through detailed experiments, microscopic and fractographic investigation, and finite element (FE) simulations. Frustum cone and pyramid components with different wall angles are formed using SPIF. Comprehensive experiments reveal that frustum cones can be successfully formed up to higher wall angles than frustum pyramids due to plane-strain deformation. Although the varying corner radius (VCR) pyramids can be formed at higher wall angles than the constant corner radius (CCR) pyramids, they tend to fail at different orientations on the same wall angle. FE simulations are performed to correlate the fracture of the components with strain accumulation and sheet thinning. Microscopic examination of the crack regions is performed to gain insight into the components' damage, crack initiation, and propagation. Damage along circumferential direction is observed in already formed regions due to bending and stretching during previous tool passes. Additionally, in higher wall angles (60 degrees and 50 degrees) VCR pyramids, the damage is observed along the meridional direction, contributing to crack initiation. The crack is primarily initiated for 45 degrees VCR and CCR pyramid due to tensile meridional stresses. Moreover, crack propagation is primarily driven by tensile meridional stresses, but shear also plays a role due to tool movement in all cases.