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.
The two beam elements available in Radioss are used on one-dimensional structures and frames. It carries axial loads, shear forces, bending and torsion
moments (contrary to the truss that supports only axial loads).
Under-integrated elements are very familiar in crash worthiness. In these elements, a reduced number of integration
points are used to decrease the computation time. This simplification generates zero energy deformation modes, called
hourglass modes.
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.
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.
Solids hexahedron and tetrahedron with linear and quadratic interpolation functions
are available in Radioss.
Linear elements are better in terms of time and memory consumption, especially due to the low
number of integration points and a larger time step ():
TETRA4:
TETRA10:
BRICK8:
BRICK20:
Table 1 summarizes the
differences between theses elements. For BRICK8, the use of
co-rotational formulation is explained in Element Library the Radioss Theory Manual; which can
avoid the accumulation of an error, due to the updating process, especially when
elements undergo large shear deformation. The formulation is not used by default for
this element and should be activated by you.
Solid elements can be degenerated to overpass some meshing problems. Degenerated elements can be
obtained by merging nodes on a same edge (hexahedron) or suppressing a middle node
in a TETRA10. The use of degenerated elements is not recommended,
but if they cannot be avoided due to complex geometry, it is important to respect
the element symmetry to keep a homogenous mass distribution. Some examples of
degenerated solid elements are shown in Figure 2.