Plastic Behavior of Metals at Large Strains: Experimental Studies Involving Simple Shear

Two experimental devices that promote simple shear are used to investigate the plastic behavior of metals under very large strains. First, researches on the anisotropic behaviors of sheets of metals performed with the help of the planar simple shear test are reviewed. In particular, it is shown that, with this device, stage IV may be reached and analyzed on polycrystals as well as on single crystals. The second part is devoted to equal channel angular extrusion, which is known to promote grain refinement after several passes. A direct comparison of the crystallographic textures measured on sheared and on extruded samples confirms that the extrusion promotes massively simple shear. Besides, the grain refinement is measured with a dedicated transmission electron microscopy (TEM) attachment. It is shown that the grain size decreases regularly for a low carbon steel as well as for copper, down to around 1 mu m. It is argued that the sustained hardening in stage IV is a mechanical signature of the grain size decrease. The trend is interpreted and reproduced quantitatively with the help of a simple modeling approach.