Rheological aspects in plasticity

Summary

One discusses several ways of improving the equations of plasticity theory by introducing rheological aspects as well. The main concepts whose meaning has been changed are yielding and workhardening. The modifications of these concepts have been suggested mainly by considering various aspects in problems of dynamic plasticity.

In order to be specific, a procedure is given to determine various functions and constants entering in a constitutive equation exhibiting both time-dependent and time-independent plasticity, starting from a set of experimental data. As typical experiments one has chosen the symmetric longitudinal impact of two identical bars, since for such kinds of problems a great deal of experimental data is available.

The unloading process is also considered since it is mainly during unloading that interesting aspects concerning “plasticity” may be put into evidence. A “relaxation boundary” which plays a main role in time-dependent plasticity is introduced. An example is given in order to show the influence of various functions or constants entering in the constitutive equation. Comparison with experimental data is excellent.

The discussion is then done for the three-dimensional problem though the experimental data are scarce. However, the one-dimensional approach is suggesting a way of defining yielding and workhardening for the three-dimensional case. Both these concepts can be introduced so that time-dependent and time-independent aspects would be present simultaneously.