Friction heat ball in round-to-half circle drawing and its effect on the material’s skin shearing

Abstract

Skin-shearing phenomenon owing to friction heat during a round-to-half circle drawing (RtHCD) is revealed using the non-isothermal finite element method assisted by the novel steady flow and non-steady temperature scheme (SFNSTS). During the RtHCD, the heated local region of the drawing die forms a friction heat ball (FHB) at the flat die side. The FHB heats the material, causing a sharp increase in the material skin’s temperature. This peculiar thermal phenomenon results in a drastic decrease in the flow stress on the material’s skin. A vicious circle of increased friction, accelerated heat, and reduced flow stress is activated, which eventually incurs the material’s skin-shearing phenomenon, experimentally and numerically validated.