MICROPLANE MODEL FOR STRAIN-CONTROLLED INELASTIC BEHAVIOUR.

Various heterogeneous brittle aggregate materials such as concretes, rocks, or sea ice, are inelastic but cannot be described as plastic, except at extremely high hydrostatic pressures. A characteristic property of such materials is that they exhibit strain-softening, i. e. , a decline of stress at increasing strain, which results from progressive development of fracture. Since these materials can undergo strain-softening within a relatively large zone, a non-linear triaxial constitutive relation is needed for its description. There are, however, some important differences from the classical modelling of inelastic behaviour, i. e. , from the theory of plasticity. In the present work, it is proposed to describe this behaviour independently on planes of various orientations in the material, called microplanes, and then in a certain way superimpose the inelastic effects from all the planes.