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rAKA/doc/manual/manual-cohesive_elements_insertion.tex
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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
the following way:
\begin{cpp}
SolidMechanicsModelCohesive model(mesh);
model.initFull(SolidMechanicsModelCohesiveOptions(_explicit_lumped_mass, true));
model.updateAutomaticInsertion();
\end{cpp}
During the simulation, stress has to be checked along each facet in order to
eventually insert cohesive elements.
This check is performed by calling the method \code{checkCohesiveStress}, as
example before each step resolution:
\begin{cpp}
model.checkCohesiveStress();
model.solveStep();
\end{cpp}
The area where stress are checked and cohesive elements inserted can be limited
using the method \code{limitInsertion} during initialization. As example, to
limit insertion in the range $[-1.5, 1.5]$ in the $x$ direction:
\begin{cpp}
SolidMechanicsModelCohesive model(mesh);
model.initFull(SolidMechanicsModelCohesiveOptions(_explicit_lumped_mass, true));
model.limitInsertion(_x, -1.5, 1.5);
model.updateAutomaticInsertion();
\end{cpp}
Additional restrictions with respect to $y$ and $z$ directions can be added as well.
\subsubsection{Intrinsic approach \label{intrinsic_insertion}}
Intrinsic cohesive elements are inserted in the mesh with the method
\code{insertIntrinsicElements}. Similarly, the range of insertion can me limited
with \code{limitInsertion}. As example with a static simulation,
\begin{cpp}
SolidMechanicsModelCohesive model(mesh);
model.initFull(SolidMechanicsModelCohesiveOptions(_static));
model.limitInsertion(_x, -1.5, 1.5);
model.insertIntrinsicElements();
\end{cpp}
Mesh data information becomes vital to the insertion of cohesive elements along
surface with more sophisticated geometry or when multiple cohesive materials are
wanted. At this purpose, cohesive elements can be easily inserted along a
specific group of surface elements identified in a GMSH geometry file. This can
be achieved, in the input file, by specifying the name of these physical groups
in the \textit{mesh parameters} section as well as their corresponding cohesive
materials. As example, with two physical surfaces named
\textit{weak\_interface} and \textit{strong\_interface} defined in the GMSH
geometry file:
\begin{cpp}
...
material %\emph{cohesive constitutive\_law}% [
name = weak_interface
sigma_c = $value$
...
]
material %\emph{cohesive constitutive\_law}% [
name = strong_interface
sigma_c = $value$
...
]
mesh parameters [
cohesive_surfaces = weak_interface,strong_interface
]
\end{cpp}
In this case, there is no need to call \code{insertIntrinsicElements} anymore
since the insertion of cohesive elements along physical surfaces is performed
automatically during \code{initFull} call.
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