Formability and failure analyses of Al/SUS bilayer sheet in single point incremental forming

Abstract

The application of single point incremental forming (SPIF) on a composite sheet can combine the benefits from process and material to achieve high formability of parts. In this paper, the deformation behaviors of Al/stainless steel (SUS) bimetal sheets have been evaluated through the experimental and numerical works. The effects of layer arrangement, tool diameter, and step down on the formability and failure modes are analyzed. The finite element method (FEM) was carried out to simulate and increase the knowledge on the deformation behaviors of Al/SUS bilayer sheet. To validate the finite element analysis, the experimental tests were performed under the same conditions. The results show that to form the Al/SUS bimetal sheet, more efforts are required and the formability of bimetal sheets is limited by the percentage of tensile reduction of area of the outer layer. Therefore, lower formability of Al/SUS bimetal sheet corresponding to the higher thinning applied on the external layer of Al/SUS bimetal sheets and this leads to increase forming force induces during the incremental forming of this layer arrangement which promotes the earlier failure in the Al/SUS compared to SUS/Al bimetal sheets. Moreover, the fracture after necking is observed in case of Al/SUS and SUS/Al layer arrangements, especially for tools with a larger diameter. Furthermore, the occurrence of the delamination of the bimetal sheets is influenced by the layer arrangement of the fractured parts.