Investigating the incremental forming capabilities of extra deep drawn steel

Abstract

Incremental Sheet Forming (ISF) is a sheet metal forming process, which relies on minimum part-specific tooling. Extra Deep Drawn (EDD) steel has been used for making door inners, dash panels, bodyside inners, etc. due to its good weldability and relatively low yield strength. However, to date very limited work is reported on ISF of EDD steel. Besides, no work, which exhaustively discusses the practicability of EDD steel for effectual incremental forming of components, is found to be reported. The present work discusses the ISF of EDD steel sheets and examines the limitations of ISF in forming the parts out of 1.0 mm thick EDD steel sheets. Two geometries, i.e., ellipsoidal cone (with varying wall angle) and truncated cone (with constant wall angle) were used as test cases to evaluate the formability of EDD steel sheets, in terms of Critical Wall Angle (CWA). Further, the formability of EDD steel with ISF is evaluated using both strain-based and stress-based forming limit curves. The thickness distribution, geometrical accuracy, forming forces, and surface roughness and hardness are evaluated in the formed components. The work, through numerical simulations and experimental analyses, investigates the process capabilities of ISF to form the EDD steel sheets in terms of formability, thickness distribution, geometrical accuracy, forming forces, and surface roughness and hardness to ascertain the scope of the proposed process.