Flexible rolling of rotational symmetric tailored blanks with a two-sided thickness profile

Abstract

Abstract The application of bulk forming operations to sheet metals leads to an increase of the material efficiency due to the enhancement of the process limits compared to conventional forming processes. The main challenges within the process class of sheet-bulk metal forming are high resulting forming forces and a defined control of the material flow. Additionally, the initial blank thickness influences the resulting quality of the geometrical and mechanical properties of functional components, like synchronizer rings. Previous investigations have shown that the application of tailored blanks with a defined one-sided thickness profile can meet these challenges which lead to an increase of the sufficient die filling of functional elements in subsequent forming processes. Due to the further increase of the geometrical complexity with functional elements in- and outside of the frame like carriers or gear teeth, the layout of the tailored blank has to be adapted. Thus, a two-sided thickness profile is necessary, for achieving the sufficient die filling of the functional elements. One possibility for manufacturing these semi-finished parts is a flexible rolling process which is used within the presented work. Thereby, it is necessary to develop a new process strategy for achieving a material thickening on both sides, rolled- as well as die-sided. For enabling a homogeneous material flow, the deep drawing mild steel DC04 with an initial sheet thickness of t 0 = 3 mm is used, due to a high formability of this material. The tailored blanks are hereby analyzed regarding the resulting process forces, geometrical dimensions like the sheet thickness, mechanical properties such as the hardness distribution and the resulting surface roughness in important areas.