2007 年 48 巻 552 号 p. 36-40
The mechanisms responsible for the formation of rectangular and trapezoidal bars by an extrusion process in which dies are inclined at various angles were investigated using numerical simulations. The greater the die inclination angle or the aperture exit angle, the smaller the radius of curvature of the extruded bar. The calculated radius of curvature agreed well with the radius observed in experiments. The particle flow pattern, one of the outputs of the simulation, was used as a basis for investigating the mechanisms of curvature generation. When the die inclination angle was increased in the case of the extrusion of rectangular bars, the volume of dead metal increased, causing material flow in the plane perpendicular to the extrusion direction. This material flow gave rise to curvature of the extruded bar. It was also found that when the cross section was trapezoidal, the asymmetry of the container aperture caused differences in material flow velocity between the top and bottom portions; these differences affected the curvature.