Deformation of strain softening materials Part I: Objectivity of finite element solutions based on conventional strain softening formulations

This paper is a continuation of the research initiated by the first author and Z. Mroz [1] during the 1980–1981 period. It is intended as a prelude to a series of articles which extend the concepts and ideas introduced at that time.In the present article, finite element analysis for conventional strain-softening concepts is provided. Sensitivity of the solution to the details of discretization (the type and number of elements) and to the strain-softening rate is discussed. The solutions obtained in this study, though unique in a mathematical sense, prove to be very sensitive to both factors. In order to avoid this sensitivity, the introduction of the geometrical strain-softening effect into the constitutive relation is recommended (after ref. [1]). An extended and generalized version of such a concept will be presented separately.