The Earthquake Engineering Online Archive

Computational models for cyclic plasticity, rate dependence, and creep in finite element analysis

Mosaddad, Bahram; Powell, Graham H.

UCB/EERC-82/26, Earthquake Engineering Research Center, University of California, Berkeley, 1982-11, 168 pages (555.1/M67/1982)

The major objective of this study has been to develop improved analytical capabilities for metal structures subjected to general loading conditions, especially cyclic and impact loading. Towards this goal, an attempt has been made to develop a reliable and efficient computational model for metal plasticity that is applicable to a wide range of stress analysis problems, including plane stress, plane strain, axisymmetric, and three-dimensional solids. A secondary objective has been the development of an improved solution strategy for analysis of the creep response of metal structures. The Mroz plasticity model was adopted from several available material models. It assumes a series of yield surfaces of the von Mises type and applies a kinematic hardening rule in which the yield surfaces progressively contact and displace each other without overlap. To extend the model for more general cyclic hardening behavior, the fields of constant plastic modulus are replaced by variable modulus fields via interpolation of the material hardening properties in an initial state and a fully stabilized state. The theory is interpreted in terms of an analogous structure. A "black box" package of FORTRAN subroutines has been developed for implementation of the material model. The capabilities of the model are demonstrated by means of a series of numerical examples. For the creep analysis study, the initial method of analysis is used and a new strategy for automatic time step selection is developed, based on controlling the change in creep strain rate during a time step.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-82-26.pdf (4 MB)