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Work
hardening (strain hardening) manifests as the increase in stress that is
required to cause in increase in strain as a material is plastically deformed.
On the diagram, the red curve is for a material that does not work harden
- an ideal plastic material. Plastic deformation begins when the yield
stress is reached and this material deforms to fracture at the same stress
value. The black curve shows the true resolved shear stress/shear strain
response of a material that work hardens. Yield again starts at the yield
stress, but as the strain increases an increase in stress is required to
maintain the same strain rate. The difference between the two curves measures
the degree of work hardening.
The
insert on the diagram shows a mechanism for work hardening. Dislocations
on intersecting slip planes permit both elastic interactions and dislocation
reactions to contribute to work hardening. |
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