|
When
a material experiences an applied stress its dimensions will change. For
low values of the stress the material exhibits an elastic strain. The stress-strain
curve shown in the diagram indicates that this elastic behavior continues
until the applied stress becomes larger than the yield stress, sy0
(red line), of
the material. At this point the material starts to show plastic deformation.
If the deformation is continued to the point D on the diagram and the stress
is then reduced to zero, the sample recovers the elastic component of the
strain but retains the plastic deformation strain component. Reapplying
the stress yields an initial elastic response with the same slope (elastic
modulus) as the initial loading, however, the yield stress marking the
transfer to plastic deformation has increased to sy1
(blue
line). The plastic deformation strain-hardened (work-hardened) the material,
increasing its dislocation density and increasing the yield stress. |
|
|
|
|
|
|
|
|
