Some Computational Issues in Large Strain Elasto-plastic Analysis

The stress integration procedure proposed by Eterovic and Bathe [Inr. J. numer. Merh. Engng 30, 1099-l 114 (1990).] is studied in detail. The elasto-plasticity formulation is based on the use of the total logarithmic strains and Cauchy stresses, and the Euler backward method of time integration. The accuracy of the procedure is assessed in the solution of various analysis problems and is compared with the accuracy of other schemes. Two important conclusions are reached. First, for a selected level of accuracy, the use of the total strain formulation, in general, allows larger time steps than the use of a stress-rate based formulation (such as a formulation based on the Jaumann stress rate). Second, the original procedure of Eterovic and Bathe can be improved in accuracy by using the trapezoidal rule with a measure to limit the magnitude of the elasto-plastic strain increment per step. This improvement allows for the change of principal stress directions during the incremental step. This capability seems to be unique to this formulation and time integration.