Hysteretic nonlinear phenomena occur in many physical processes: ferromagnetism, adsorption, cyclic plasticity in mechanics, phase transformations, economics, etc. It is characterized by the fact that the same instantaneous values of input can give different outputs depending on the history of the input applied. It means that the relationship is not only nonlinear but also multivalued making it very difficult to model and control. In this paper, accent was given to the application to mechanics i.e. to cyclic plasticity of trusses.