Investigation on surface roughness and sub-surface damage in ISF

Abstract

Incremental sheet forming is a potential technology in future manufacturing. However, the surface roughness increases during the process can limit the geometric accuracy and alter the mechanical properties of the product. The paper presents an extensive experimental investigation on the relevance between the surface roughness and sheet thickness using the two points incremental forming and an optical microscopy analysis the microstructure change in the sheet material during forming. Firstly, aluminium alloy sheets with different thickness were formed into a benchmark shape. Then the measurements of sheet thickness and wall angles were carried out to reveal the effects on the surface roughness that is further related to the mechanical properties. Finally, the microstructure of the sheets prior and after forming was investigated under microscope, considering the influence of grain size and clad layer. It is shown that a large wall angle leads to a worse surface finish. However, there was no direct relationship found between sheet thickness and surface roughness. Through the microstructure observation of processing sheets, it is found that the bounding of the clad layer remained intact and the deformation is constrained within the clad layer. [Submitted 19 March 2017; Accepted 7 October 2017]