Formability and Effect of Hole Bridge in the Single Point Incremental Forming

This paper studies the mechanical properties, formability and effect of hole bridge (hole lancing) in the single point incremental forming for Al5052-O with the thickness of 0.8 mm. The mechanical properties, including anisotropy property and stress-strain relation, were evaluated by uniaxial tensile tests in three directions of 0 degrees, 45 degrees, 90 degrees with the rolling direction. Varying wall angle conical frustum test was used to study the formability. The forming parameters of tool diameter, step depth, spin speed, and feed rate were optimized using multi-objective optimization with grey relational grade. The results show that the tool diameter strongly influences formability, springback and thickness reduction. To verify the effect of hole bridge on the formability, a predesigned hole bridge was machined by a laser on the blank shoulder nearby the forming periphery before forming. The optimized forming parameters found in previous step were applied for this test. As the result, the maximum forming angle was significantly improved in comparison with the non-hole-bridge part. Finite element simulation by ABAQUS explicit software was used to explain the strain evolution in the blank with cut-off hole of the incremental forming process. The simulation results were compared with experiment and discussed.