The analysis becomes non-linear in some remarkable cases:
– the material exhibits a non-linear behavior, ie the tension / deformation traction curve cannot be adequately interpolated with a straight line;
– the structure undergoes significant deformations under load;
– in the realization of the model particular elements called “contact” elements were used, which consider the possibility that two different interfaced structures may or may not come into contact depending on the stresses to which they are subjected.
Non-linear analysis is considerably more expensive and critical from a numerical point of view; it is performed by imposing the load with incremental step, assuming that, within each step, the behavior of the structure can be linearized. Specific numerical indicators allow to evaluate in how many steps the analysis must be divided so as to converge to a result.