Date of Award
Doctor of Philosophy (PhD)
Civil and Environmental Engineering
George Z. Voyiadjis
The path-dependent and nonlinear behavior of metallic materials subjected to cyclic loading is modelled using the proposed hardening rule. It uses mainly two surfaces, a yield and a limit surface and includes the memory effects through a separate surface called the memory surface which is obtained from a maximum stress criterion. The model considers the facts that the motion of the center of the yield surface in the stress space is mainly governed by the direction of the deviatoric stress rate and that the uniqueness of the solution requires nesting of the two surfaces. The model proposed satisfies both conditions through a blending operation which introduces a smooth transition from one rule to the other. The nesting of the two surfaces is guaranteed by the introduction of a limit surface motion that is dependent on the yield surface motion. Ratchetting is one of the most difficult of the loading histories to correlate using the plasticity models. The prediction of the nonproportional ratchetting response is quite satisfactory compared to the other existing models. A two surface finite stain, rate-dependent/viscoplastic constitutive model is also proposed in this work as an extension of the proposed time-independent model. An updated Lagrangian finite element program is developed incorporating the proposed constitutive model in order to solve real world problems.
Sivakumar, Srinivasan Madras, "A Non-Proportional Cyclic Plasticity Model for Metals With Ratchetting Effects." (1993). LSU Historical Dissertations and Theses. 5672.