Experimental investigation of mechanical properties, formability and force measurement for AA7075-O aluminum alloy sheets formed by incremental forming

Incremental sheet forming (ISF) has demonstrated its high potential to shape complex three-dimensional components without using specific tooling, thus enabling product customization, cost reduction and efficiencies. This paper presents an experimental campaign to investigate AA7075-O aluminum alloy sheet forming using single point incremental forming (SPIF) technology and understand the forming process mechanism. Firstly, tensile tests were carried out to characterize the mechanical properties of AA7075-O sheets with three different thicknesses. Then, the effects of tool path types with different incremental steps on the maximum part draw angle and the successful part height were evaluated to clarify the formability. Additionally, a fracture forming limit diagram was developed to give the design limits for strain. Finally, the trends in forming forces were analyzed considering the influence of different draw angles, sheet thicknesses, step-down sizes and sheet orientations. Experimental results showed that formability is affected by the part draw angle and incremental steps of the tool path. However, the likelihood of successful forming also depends on other geometrical design parameters such as the part height. In addition, the influences of process parameters on tool forces provide further insights into the deformation mechanics of AA7075-O sheets. The slope of the force curve after the peak value can be identified as a forming failure prediction indicator regardless of the tool path types when using a truncated cone as a benchmark. Also the influence of sheet orientations on forming forces was investigated in SPIF. The vertical forming force is found to be smaller in a sheet orientation 45 to the rolling direction than that of a sheet orientation 0 for three different sheet thicknesses