Implicit Shape Function Orders

Some solid mechanics formulations contain other degrees of freedom in addition to the displacements. The shape functions are then selected internally based on your choice of displacement discretization.

Viscoelastic Stress and Strain

When using a viscoelastic material model, auxiliary degrees of freedom are added either for the viscoelastic strains or the viscoelastic stresses, depending on whether a linear or a nonlinear formulation is used. These degrees of freedom are local to the element, and you can select either the discontinuous Lagrange or Gauss-point data type.

The discontinuous Lagrange shape functions will have an order that is one below what is used for the displacement shape functions.

If Gauss-point data is used, the same integration points as used for the numerical integration of the stiffness matrix are used. This order depends on the selected displacement discretization order and whether reduced integration is used or not.

Inelastic Strains

For material models like plasticity and creep, the inelastic strains are formally degrees of freedom. They will be allocated at the same integration points that are used for the numerical integration of the stiffness matrix. This order depends on the selected displacement discretization order and whether reduced integration is used or not.