6. D modeling#

6.1. Characteristics of modeling#

The calculation is repeated with the viscoplastic model (ROUSS_VISC) in modeling A, adding viscous regularization (REGU_VISC).

Two parameters must be determined for this mechanism of regulation by viscoelasticity:

stiffness k: the apparent stiffness (k+ negative work hardening) must always be positive. If k is not big enough, we can end up in the situation where there would be no solution, even with viscosity. In this modeling, \(k\) is chosen at the value of the Young’s modulus \(E=2.e5\mathit{MPa}\).
The characteristic time \(\mathrm{\tau }\): we first estimate the deformation rate at each point in such a nice situation. At this rate of deformation, it takes a certain amount of time to cross the elastic domain. \(\mathrm{\tau }\) must be small (1 to 10%) compared to this time. More details will be in the internal note EDF R&D 6125-1724-2020-01606. In this modeling, the displacement of 10 mm is imposed along the length side (Y direction) by 10 mm for 10 s. This requires approximately 1.35e-4 s to reach 10% of the elastic limit (27 MPa). The value 1.0e-4 s is chosen for \(\mathrm{\tau }\).