Non-viscous geomaterials
Elasto-visco-plastic constitutive models of geomaterials

If the behavior does not depend on physical time, this means in particular that the incremental response will not depend on the time increment dt during which the incremental solicitation was applied. So, whether you walk quickly or slowly on the sand of the beach, the footprint you leave is identical.

Consequently, the incremental function F will be independent of the time increment dt. We can therefore either express dσ as a function of dε, or the inverse (insofar as the incremental relationship is invertible):