Biomedical Engineering Reference
In-Depth Information
The geometry of this tool provides that the material is deformed
by simple shear at ideal, frictionless, and conditions. The cross section
of the specimen remains about equal before and after a processing
step, thus it is possible to subject one specimen several times to ECAP
in order to reach highest degrees of plastic deformation. A circular
or squared cross section of the channel provides the possibility of
a materials processing at different routes that are distinguished by
their different combinations of sample rotation around the channel
axes between consecutive processing steps.
4.3.2
Cyclic Extrusion Compression Method
Richert J. and Richert M. came up with the idea of cyclic extrusion
compression method (CEC) [38]. CEC involves the cyclic low of
metal between the alternating extrusion and compression chambers
(Fig. 4.8). The deformation effect could obviously be achieved with
the frame/die ixed and the movable punches or vice versa.
Figure 4.8
Reciprocating extrusion compression method.
4.3.3
High Pressure Torsion
High Pressure Torsion (HPT) is one technique of severe plastic
deformation and provides a continuous shear deformation of the
metallic material. In Fig. 4.9, a sketch of a HPT tool is shown. In
principal, a disc shaped sample is deformed by pure shear between
two anvils that are rotating with respect to each other. The necessary
torsion-momentum is provided by friction forces at contact areas
anvil-material.
