Blind insertion is the simplest insertion method, by which a cohesive element is placed directly between the volumetric elements, without thought to the local stresses or stability of the system. Figure 4.8 and 4.9 presents the nodal separations for the tracking node of the insertion case using the "horizontal" and "mixed" cohesive elements.
When the cohesive elements are present at the start of the simulation, the nodal separations are simply increasing due to the applied constant velocity. On the other hand, when insertion occurs after some time, the nodal separations oscillate severely around the reference solution. The amplitude of these oscillations is directly proportional to the local stress at the time of insertion, which increases over time for a constant velocity loading, as seen in Figure 4.7.