An analytical technique, which employs the approach of viscoplasticity for evaluating large plastic strains such as those occurring in metalforming, is presented. The distortion of a quadrilateral element of a grid was tracked to compute strains during deformation. Here, two lines of a quadrilateral are used (length before and after deformation and direction cosines before deformation) to determine the true effective strain in the element. Although the method can be applied to any mode of deformation, its application plane-strain deformation is considered. The method has been verified by application to basic cases of deformation such as uniaxial compression, tension, pure shear, and rotation of element. Wedge testing was used for verification of the analytical results of a viscoplastic finite-element program ALPID which was developed to simulate metal flow in deformation processes such as forging and extrusion. Wedge-shaped specimens were machined from plates of 1100-F and 6061-T6 aluminum, and grids were engraved on the meridian plane by means of a CNC engraver. The specimens were annealed and compressed in a channel-shaped segmented die at room temperature.
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