2. Mechanical analysis of tests

2.1 Compression tests

The main advantage of this first category of hot rheological tests lies in the imposed deformation path, similar to those encountered in forging (uniaxial compression) or rolling (plane compression). In contrast to the torsion test, the deformation rate is theoretically uniform in the absence of friction between the sample and the tools, so that entry into the plastic deformation regime takes place at virtually the same instant at every point of the material tested.

Compression testing is therefore well suited to determining mechanical behavior at low deformations, particularly at room temperature where the use of a high-performance lubricant (Teflon™ film) minimizes the effects of friction. On the other hand, friction plays a considerable...