Elements of Plasticity Theory

This chapter discusses the elements of the plasticity theory. The transition from elastic to plastic deformation of hot-finished, low-carbon steel is often characterized by a material instability known as the Liiders strain. The macroscopic effect of the instability is inhomogeneous deformation. The inhomogeneous nature of the deformation is also illustrated through tensile tests on strips made from similar type steels. The strips were coated with a brittle lacquer that shattered at a strain in the range of 1–2%. Lighter colors represent relatively deformed materials (shattered coatings), and dark colors represent relatively undeformed materials. The two regions are separated by a relatively sharp and inclined front. The front is seen to propagate from the left to fight at nearly constant speed.