For cohesive material, \akantu has a pre-defined material selector to assign
the first cohesive material by default to the cohesive elements which is called
\code{DefaultMaterialCohesiveSelector} and it inherits its properties from
\code{DefaultMaterialSelector}. Multiple cohesive materials can be assigned
using mesh data information (for more details, see \ref{intrinsic_insertion}).
\subsection{Insertion of Cohesive Elements}
Cohesive elements are currently compatible only with static simulation and dynamic simualtion with an explicit time integration scheme
(see section~\ref{ssect:smm:expl-time-integr}). They do not have to be
inserted when the mesh is generated but during the simulation. At any time during the simulation, it is possible to access the following energies with the relative function:
\begin{cpp}
Real Ed = model.getEnergy("dissipated");
Real Er = model.getEnergy("reversible");
Real Ec = model.getEnergy("contact");
\end{cpp}
\subsubsection{Extrinsic approach}
The dynamic insertion of extrinsic cohesive elements should be initialized