COMPLAS 2023

A Nodal-Based Finite Element Implementation of Plasticity and Damage Models Using a Stress-Displacement Formulation

  • Codina, Ramon (Universitat Politècnica de Catalunya)

Please login to view abstract download link

In this work we present a nodal based implementation of an otherwise standard finite element approximation of plasticity and damage models in solid mechanics. This implementation is based on an a priori calculation of the integrals appearing in the formulation and then the construction of the matrix and right-hand-side vector of the final algebraic system to be solved. After appropriate approximations, this matrix and this vector can be constructed directly for each nodal point, without the need to loop over the elements and thus making the calculations much faster. In order to be able to do this, all the variables have to be defined at the nodes of the finite element mesh, not on the elements. This implicitly implies a mixed stress-displacement approach, and therefore either inf-sup stable approximations are used or stabilised finite element approaches are employed; the latter option is adopted in this work, permitting in particular equal continuous interpolation of displacements and stresses. An iterative scheme is devised so that the calculation of the displacements is uncoupled from that of the stresses. Likewise, the constitutive equation needs to be integrated (in time) at the nodes of the mesh, rather than at the (spatial) integration points. The constitutive laws chosen to describe our methodology are rate independent plasticity and a simple damage model, both assuming infinitesimal strains.