An explicit is solved by calculating results in small time increments or time steps. The size of the time step depends
on many factors but is automatically calculated by Radioss.
Composite materials consist of two or more materials combined each other. Most composites consist
of two materials, binder (matrix) and reinforcement. Reinforcements come in three forms, particulate,
discontinuous fiber, and continuous fiber.
When rupture is modeled and elements are expected to fail, it is important to deal with failed elements defined either
as a master segment, or as slave nodes.
Optimization in Radioss was introduced in version 13.0. It is implemented by invoking the optimization capabilities of
OptiStruct and simultaneously using the Radioss solver for analysis.
In an FE model, initial penetrations are very common, are unavoidable and result from the
discretization during the meshing process (Figure 1).
Inacti
Special treatment for initial penetrations can be accomplished through the use of the Inacti flag. It is possible to remove penetrated nodes from the interface or to remove
the master segments relating to the penetrated nodes. Both treatments allow getting
rid of initial penetrations very easily, but they may lead to poor results if the
number of penetrated nodes is large.
Setting Inacti
to 3 allows Radioss Starter to automatically modify the
coordinates of penetrated nodes to avoid initial penetrations. Special care must be
taken when doing so, since this operation can lead to initially constrained
springs.
It is also possible to obtain a variable gap in time by setting Inacti to 5. The illustration Figure 2 explains how the effective gap is updated taking into account the
previous penetrations.
At t=0, if a node is initially penetrated, its gap is automatically corrected. Then this
"initial corrected gap" will be increased every time the node is
moving away from the master segment. This option is mainly used for unfolding the
airbag, it allows a decent time step at the beginning of the unfolding, whereas
nodes are all highly penetrated.
To avoid high frequency effects Inacti = 6 is recommended instead of Inacti =5.
Fpenmax
Fpenmax
(maximum fraction of initial penetration), is used to deal with big initial
penetration. Node stiffness will be deactivated, if , whatever the value of Inacti.
Igap3 + %mesh_size
With Igap= 3
and %mesh_size, the size of the mesh can be taken into account to
avoid initial penetrations. In this case, the variable gap is computed
as:(1)
Where,
Length of the smaller edge of element
Length of the smaller edge of elements connected to the slave node
Irem_gap
The option Irem_gap is used to deactivate slave nodes which close (Curvilinear ) to elements. This option is useful for self-impact
contact when mesh size is very small.
Note: When dealing with initial penetrations, it is strongly
advised to remove initial penetrations during the creation of the FE model,
using pre-processing tools like HyperMesh and
HyperCrash depenetrators.