Plastic deformation processing rolling

Plasticity. Slip, the gliding motion of full planes of atoms or partial planes, called dislocation, allows for the deformation processing of polycrystalline metals (forging, extrusion, rolling, swaging, and drawing). Slip occurs much more readily across close-packed planes in close-packed directions. 

One of the ways in which shapes can be produced in order that manufacturing processes can subsequently be carried out is by rolling. This can be performed as hot rolling or cold rolling - in each case, the metal is worked while in a solid state and is shaped by plastic deformation. 

The yield point phenomenon is often not desired because it causes an inhomogeneous plastic deformation. In deep drawing of metal sheets for car bodies, for instance, the surface of the sheets becomes rough (so-called orange peel ). Counter measures are therefore needed. Steel sheets, for instance, are usually temper rolled before the deep drawing process to tear off the dislocations by minor plastic deformation. 

The methods by which chain orientation is created may be divided into solid-state and liquid processes. Solid-state processes involve a plastic deformation of an isotropic or weakly anisotropic solid. Glassy amorphous polymers can only be drawn to moderate strains. The polymers which can be substantially oriented are semicrystalline with deformable amorphous (T > Tg) and crystalline phases. The remaining discussion in this chapter is confined to this group of polymers. Deformation can be achieved by colddrawing, extrusion or rolling (Fig. 9.17). 

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