It was emphasized that elastoplastic deformation proceeded via defects in an ordered crystalline structure. The most important were the defects which produced plasticity motion at all temperatures. It was shown that, for 2 reasons, the elastoplasticity of crystalline solids did not fit well into the scheme of continuum mechanics. That is, the conventional tensor of dislocation density counted excess dislocations of only one sign, while the observed hardening and softening was due to dislocations having 2 signs. The motion of the typical defects in a crystalline structure destroyed the particles which constituted the body. It followed then that the elastoplastic crystalline solid was not a differentiable material manifold. During elastoplastic deformation, an irregular dislocation network developed that could be seen in an electron microscope. The network could be described by an infinite set on n-point correlation functions of dislocations. It was proposed that solutions could be classified as being of first-, second- or third-order; according to the highest order of correlation function which was included. The first-order theory was the so-called mean field theory. The 2-point autocorrelation function gave the total length of dislocations in a unit volume.

Benefits and Shortcomings of the Continuous Theory of Dislocations. E.Kroner: International Journal of Solids and Structures, 2001, 38[6-7], 1115-34