Numerical simulation and experimental investigation of incremental forming of non-axisymmetric aluminum sheet parts without a peripheral blank holder

This study investigates the incremental forming of shallow non-axisymmetric AA6061-T6 aluminum sheet parts without the use of a peripheral blank holder. While most previous studies focus on axisymmetric geometries or constrained blank conditions, the feasibility and deformation behavior of free-edge non-axisymmetric parts remain insufficiently understood. In this work, five different single-stage and multi-stage toolpath strategies are experimentally and numerically evaluated for sheets with free-edge lengths of 6, 10, and 14 mm. The results demonstrate that non-axisymmetric parts can be successfully formed up to a height of 10 mm using multi-stage strategies without peripheral support. Among the investigated approaches, the incremental angle-increase strategy with decreasing diameter improved thickness distribution by up to 7% compared to other strategies. Distinct fracture modes were observed depending on the free-edge length and toolpath design, including circumferential corner cracking and radial edge cracking. Furthermore, analysis of in-plane strain evolution revealed a significant change in strain-path slope at the onset of fracture for larger free edges. These findings provide new insights into deformation stability and fracture mechanisms in free-edge incremental forming of non-axisymmetric geometries.