Orientation and residual stress distribution in plastic sheet extrusion

The purpose of this study is to develop a theoretical model which can describe the stress distribution in extruded sheets under extremely low or almost no draw conditions. Experimental data show that, at higher draw ratios, the sample extruded from the larger die gap possesses a higher surface orientation. In such cases, the final stress of the extrudate probably results more from the elongational drawing after the material emerged from the die than from the shear flow inside the die. For thicker extrudates, the cooling rate would be slower and, consequently, the extrudate would be subject to more elongational drawing before solidification.