That was in agreement with higher inelastic deformation after reaching the yield point
At a given temperature, the upper yield points
, plastic deformation stresses, and fracture stresses increase with increasing strain rate.
the as-molded materials), the material strain softens: the nominal stress drop occurs just past the yield point
due to the failure and disconnection of the lamellas and remains stationary while the tie molecules are pulled out from the fragmented lamella and become part of the amorphous layers.
There were two knee-like yield points
on stress--strain curves of specimens twisted counterclockwise.
When increasing the radiation dose, the tensile strain at yield point
decreases, down to 49.
The tensile curves suggest the existence of two yield points
for this polymer, which can be more clearly distinguished at high temperatures.
While the tensile force-strain curves along the MD do not reveal a distinct yield point
(relative maxima in force), the traces appear to indicate the existence of two yield points
, a phenomenon noted previously in polyethylene blown films (23) and isotropic specimens [36, 37].
These results also suggest that the large scale chain reorganization is induced in the neighborhood of the yield points
for the i-PP and the incompatible blends, whereas the deformation process for the reorganization continuously and smoothly occurs for the compatible blends.
We recently have proposed a theoretical approach of the plastic deformation of polyethylene and related copolymers displaying double yield points
owing to two models borrowed from the solid state physics.
They observed double yield points
for three samples.
However, neither the structural conditions necessary to observe multiple yield points
nor the generality of this behavior were explored.
Engineers who are used to working with metals are surprised that plastics cannot operate as close to their yield points
as can metals.