Forming mechanism of a novel shape-surface integrated incremental sheet forming process for fabricating parts with enhanced surface functionality

Abstract

Metallic components with surface microfeatures are increasingly used in aerospace, automotive and other applications due to their drag-reducing properties. In this situation, we proposed a novel shape-surface integrated incremental sheet forming (S2-ISF) process to achieve the simultaneous fabrication of both surface microfeatures and desired geometric shape. It was found that an increase in the forming angle was most effective in improving the formation of microgroove array, followed by the step size, the spindle speed and the feed rate. Moreover, when the forming angle is constant, the step size and microgroove pitch increase linearly. Compared to the as-received sheet, the yield strength is increased by more than 20% after the S2-ISF process. Moreover, we observed that the increase of forming angle in the S2-ISF process has promoted grain deformation and grain fragmentation, which is favorable for the formed part to obtain more uniform and finer grains. The grain size distribution along the thickness direction shows the characteristics of ‘coarse in the middle and fine at both ends’. Finally, we found that the formed parts with different microgroove pitch from the S2-ISF process have the significant enhancement on the hydrophobicity and anti-friction property. When microgroove pitch is 155.5 μm, the surface contact angle of formed part improved from 70.65° to 101.39°, and the wear volume of formed part decreases from 4.89 × 10−3 mm3 to 3.65 × 10−3 mm3. This work provides a solution for the efficient and economical fabrication of three-dimensional thin-walled parts with microgroove array to enhance surface functionality.