Modeling of cyclic plasticity with application to steel and aluminium structures.

摘要

This report deals with the development of a reliable and accurate constitutive model for cyclic metal plasticity which is amenable to an efficient implementation in non-linear finite element codes. The model is based on the bounding surface plasticity theory and the concept of plastic internal variables in thermodynamics. Non-linear isotropic and kinematic hardening rules are adopted, and additional internal variables are introduced to describe material characteristics observed in experiments. Numerical algorithms are formulated to integrate the incremental constitutive equations. In the present study, three different integration algorithms are implemented for the cyclic plasticity model, namely the adaptive improved Euler method, the cutting plane method and the closest point projection method. An experimental programme, comprising uniaxial and biaxial cyclic tests, is conducted to investigate the material properties (yield criterion, isotropic and kinematic hardening, mean stress relaxation, memory of prior strain histories and cross-hardening effects) of the aluminium alloy 6060 in temper T4 and T6. Tests of perforated plates subjected to monotonic and cyclic in-plane loads are performed. The purpose of these tests is to evaluate numerical results obtained by use of the finite element method and the proposed model of cyclic plasticity for application to aluminium alloys. The constitutive model is implemented in the general purpose non-linear finite element code FENRIS for plane stress analysis with membrane and thin-shell elements. Material and geometric non-linear problems involving structural components subjected to monotonic and cyclic loads are analyzed, and the results are compared with experimental studies. 117 refs., 139 figs., 24 tabs.