What causes the distinctive saw-tooth chips that form when machining hardened steels? This research investigates the mechanisms behind this phenomenon, a key characteristic of machining hardened steels with geometrically defined cutting tools. It challenges previous explanations by focusing on the role of adiabatic shear. The study presents results indicating that the primary instability leading to saw-tooth chip formation is the initiation of adiabatic shear at the tool tip, propagating towards the free surface. The research identifies a transition in the morphology of continuous chips, from a lamellar structure to a "fold-type" structure, attributed to thermally softened micro-shear zones. The findings provide a new perspective on the mechanisms of chip formation in machining hardened steels, suggesting that adiabatic shear initiation plays a critical role. This understanding can contribute to optimizing machining processes and improving the quality of manufactured parts.
Appearing in the Journal of Manufacturing Science and Engineering, this paper aligns directly with the journal's focus on advancing manufacturing processes and technologies. By investigating the fundamental mechanisms of chip formation in machining, it provides valuable insights for engineers and researchers seeking to optimize manufacturing operations.