A Comprehensive Experimental Investigation of Hydraulically Supported Robot-Assisted Incremental Sheet Forming of Al6061 Sheets

Abstract In the current study, robot-assisted incremental sheet forming (RAISF) was performed on 1.05 mm thick sheets of aluminum alloy 6061, which was supported from underneath by fluid; this process is named robot-assisted incremental sheet hydroforming (RAISHF). A variable wall angle conical frustum was fabricated, both with and without the fluid support. The cone formed by RAISHF was 6.67% steeper and 28.47% deeper than with RAISF alone. Spring back was reduced by 77.14%, suggesting better accuracy of the formed part. The role of fluid pressure in enhancing the performance of RAISHF was explained by considering a through-thickness element under equilibrium conditions. For cones of identical wall angle formed with RAISF and RAISHF, the thickness distribution, tensile properties, microhardness, major and minor strains in the plane of the sheet, microstructure, and residual stresses were characterized, with RAISHF exhibiting more uniform thickness distribution, more even strain distribution, and less hardening. X-ray diffraction revealed the residual stress on the surface of the cone in both processes to be tensile, with RAISHF showing lower residual stress. Microstructure of the samples taken from formed cones revealed that, due to dynamic recrystallization, more strain can be obtained by RAISHF.