Mechanical Properties

· Some materials, such as well annealed low carbon steels, show two yield points.
· Local deformation (Luders bands) starts at the upper yield point and these bands propagate through the test section with a stress equal to the lower yield point, σ_y .

· Once the Luders bands fill the test section, normal plastic deformation continues throughout the test length.

From: Callister, "Materials Science and
Engineering," Wiley (1994)

From: Hull, "Dislocations," Pergamon (1965)