# Dynamic¶

The analysis type **Dynamic** allows the time-dependent calculation
of displacements as well as stresses and strains in one or multiple
solid bodies. In contrast to static analyses, inertia effects are taken
into account and the simulation proceeds in real time steps.

In the post-processing it is possible to analyse single time steps as well as the dynamic performance as function of time. Similar to a Static analysis you can check for undesired deformations or critical stresses and modify your design based on those learnings.

In the following the different simulation settings you have to define are described in detail as well as the various options you can add.

## Domain¶

In order to perform an analysis a given geometrical domain you have to discretize your model by creating a mesh out of it. Details of CAD handling and Meshing are described in the Pre-processing section.

After you assigned a mesh to the simulation you can add some optional domain-related settings and have a look on the mesh details. Please note that if you have an assembly of multiple bodies that are not fused together, you have to add Contacts if you want to build connections between those independent parts.

## Model¶

In the model section everything that defines the physics of the simulation is specified e.g. material properties, boundary conditions etc. On the top level you can adapt some generic settings. For this analysis type you can add a graviational load for the whole domain and define if you want to run a geometrically linear or nonlinear analysis.

### Materials¶

In order to define the material properties of the whole domain, you have to assign exactly one material to every part. You can choose the material behavior describing the constitutive law that is used for the stress-strain relation and the density of the material. Please note that the density is used for volumetric loads e.g. gravitation. Inertia effects are only considered in dynamic simulations (Dynamic). Please see the Materials section for more details.

### Initial Conditions¶

For a time dependent behaviour of a solid structure it is important to define the
Initial Conditions carefully, since these values determine
the solution of the analysis. In a **Dynamic** analysis the displacement and velocity need to be defined initially,
as they determine the initial state of the domain before the loads and constraints are applied.
Per default the displacement and velocity are initialized as zero length vector.
Thus if you use the default values there will be no displacement and velocity
in the initial state.

### Boundary Conditions¶

In a **Dynamic** analysis you can define Constraints (Displacement boundary conditions)
and Loads (Force boundary conditions). If you want to determine
the position of a part of the domain, add at least one displacement constraint
in every coordinate direction. Otherwise it is allowed to move freely in space.
This is intended for e.g. drop tests.

In case of missing force boundary conditions (including gravitation), the geometry becomes load-free and apart from the prescribed displacement boundary conditions (constraints) no deformation will evolve. However, this might be intended to determine the strain distribution e.g. in pre-clamped structural components.

Constraint types (Displacement boundary conditions)

Load types (Force boundary conditions)

## Numerics¶

Under numerics you can set the equation solver of your simulation.
The choice highly influences the computational time and the required
memory size of the simulation. For a **Dynamic** analysis you can also
define the time integration scheme at this point.

## Simulation Control¶

The Simulation Control settings define the overall process of the calculation as for example the timestepping interval and the maximum time you want your simulation to run before it is automatically cancelled.

## Solver¶

The described **Dynamic** analysis using the finite element code CalculiX Crunchix (CCX)
is only available via the **solver perspective**.
You may as well choose the finite element package **Code_Aster** for this analysis type
(Dynamic analysis CA)
using the standard **Dynamic** analysis from the **physics perspective** or via the **solver perspective** choosing **Code_Aster** as solver.
See our Third-party software section for further information.