ИСТИНА

http://www.ecf22.rs/timetable.html The rubber manifests so many properties appearing illogical and contradictory each other that they give the challenge to put forward a model to describe some of them and not go against any other. Among these properties we need to emphasize the following: - anisotropy of Mullins effect (reduction of elastic hysteresis is well pronounced for successive loading in the direction of pre-stretching and almost absent in the direction normal to pre-stretching); - less pronounced Mullins effect under bi-axial stretching than under uniaxial stretching; - anisotropy of swallowing after uniaxial stretching, with emphasis on reduction of expansion in the direction normal to pre-stretching; - reinforcement in the direction of pre-stretching and reduction of strength in the direction normal to pre-stretching (especially pronounced in tearing tests). A model allowing qualitative qualitiave description of the mentioned phenomena altogether is suggested based on the concept of slippage of molecular chains over the particles of carbon black or strain induced crystals. The basic assumptions of the model is the following: - elastic moduli in any direction is proportional to the number of molecular chains aligned in this direction (and close directions) and decrease with the chain lengths (according to the classical theory of rubber elasticity); - sliding of polymer chains over the particles of carbon black or strain induced crystals leads to redistribution of chains lengths, particularly to elongation of the chains aligned along the tension direction; - the total amount of segments forming the molecular chains conserves during loading; increase in the chain length in the direction of tension is compensated with decrease in the chains number in other directions. The model was realized in the simplest form of the finite number of chains model with a minimal number of parameters. Illustrative examples are provided.