Effect of tool profile on micro hardness, forming limit, and final thickness in incremental hole flanging process of DC01 steel and AA1050 sheet metals

Abstract

The present study delves into the incremental hole flanging process applied to AA1050 and DC01 sheet metals with 0.7 and 1 mm thicknesses. Employing a distinctive lathe-based fixture, the process utilizes a proposed tool profile and fixture incorporating mutually spinning and rolling motions. The investigation covers three forming angles (72°, 90°, and 45°) and three different rotational forming speeds (170, 350, and 525 RPM). The primary objective is to assess the impact of tool forming angle, forming speeds on microhardness, thickness ratio, and forming limit diagram. The study employs a microhardness test, measurements of flange height, and final thickness. Results revealed hardness and thickness variations depending on material type sheet thickness, showing a critical forming speed at which a critical change in variation trend occurs irrespective of forming angle. Forming speed and tool profile were selected carefully to produce a maximum forming limit and a large amount of plastic deformation with no failure of metals. Hardness distribution experienced smooth variation, and the maximum increase in post hardness didn’t exceed 73% without evidence of crack formation at the end of the process. As well as the thickness distribution shows a uniform variation along the flange profile with a maximum thickness reduction of 40% and 51% for 1 mm DC01 and AA1050 sheets, respectively. Finally, based on the proposed tool geometry and holding arrangement adopted in the present work, results indicated a good enhancement in forming limit is satisfied with no obvious large thinning occurring due to change in deformation modes can be used successfully in incremental hole flanging process.