SOME COMPUTATIONAL ISSUES IN LARGE-STRAIN ELASTOPLASTIC ANALYSIS

The stress integration procedure proposed by Eterovic and Bathe [Int. J. numer. Meth. Engng 30, 1099-1114 (1990).] is studied in detail. The elasto-plasticity formulation is based on the use of the total logari thmic strains and Cauchy stresses, and the Euler backward method of ti me integration. The accuracy of the procedure is assessed in the solut ion of various analysis problems and is compared with the accuracy of other schemes. Two important conclusions are reached. first, for a sel ected level of accuracy, the use of the total strain formulation, in g eneral, allows larger time steps than the use of a stress-rate based f ormulation (such as a formulation based on the Jaumann stress rate). S econd, the original procedure of Eterovic and Bathe can be improved in accuracy by using the trapezoidal rule with a measure to limit the ma gnitude of the elasto-plastic strain increment per step. This improvem ent allows for the change of principal stress directions during the in cremental step. This capability seems to be unique to this formulation and time integration.