6. Summary of results

The use of discrete elements, assigned to nodes or segments, with a dis_contact material and used with stat_non_line (comp_incr behavior, dis_shock relationship or DIS_CONTACT) makes it possible to model a unilateral behavior of springs.

In \(\mathrm{2D}\) as in \(\mathrm{3D}\), the use of the rigi_parasol keyword from the affe_cara_elem command makes it possible to assign stiffness to the springs that are proportional to the length or the area of the elements to which they are connected.

Since the behavior is one-sided, it is necessary for Code_Aster to do several iterations to find the balance position. It is also possible to encounter convergence problems associated with a loss of precision, due to poor conditioning of the stiffness matrix during iterations. The stiffness of the springs can be cancelled out from one iteration to the next.

Regarding modeling by interface elements, the continuous solution is obtained without errors. Again, several iterations are necessary to find the point of detachment of the plate. Ideally, one should also avoid the energy-free mode in which the plate takes off everywhere (it could lead to a non-invertible matrix, even if this has not been observed because, in the natural state, compression stiffness is preferred, which is not zero).