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.
A rigid body is defined by a set of secondary nodes and a main node. It can be compared to a part with an infinite
stiffness. No relative displacement is allowed between secondary nodes, and the general motion of the rigid body manages
the main node.
A rigid wall is a nodal constraint applied to a set of secondary nodes in order to avoid the node penetration to the
wall. If contact is detected, then the secondary node acceleration and velocity are modified.
Interface TYPE2, also called tied interface is a nodal constraint to rigidly connect a set of secondary nodes to a main surface. The secondary nodes forces and
moments are transferred to the main nodes, and then secondary nodes are positioned kinematically according to the
motion of the main nodes.
A cylindrical joint is like a rigid body, except that one specific direction is defined with the first two secondary
nodes. All nodes are free to move along this direction and to rotate around it.
The rigid link option imposes the same velocity on all secondary nodes for one or more directions. Directions are
defined to a skew or a global frame, velocity is computed with momentum conservation.
Gear type joints are more complex than other kinematic joints. They use the Lagrange Multiplier method and
are compatible with all other Lagrange Multiplier kinematic conditions and incompatible with all classical
kinematic conditions.
As nodal constraints are based on kinematic conditions applied on nodal DOF, therefore it is not allowed to apply
two nodal constraints to the same set of nodes, unless the induced kinematic conditions are perfectly orthogonal (for
example: boundary condition in the X-direction and rigid link in the Y-direction).
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.
A cylindrical joint is like a rigid body, except that one specific direction is defined with the first two secondary
nodes. All nodes are free to move along this direction and to rotate around it.
A cylindrical joint is like a rigid body, except that one specific direction is
defined with the first two secondary nodes. All nodes are free to move along this direction
and to rotate around it.
A kinetic condition is applied on all secondary nodes, including the first two defining the
privileged direction No main node is used.
If all the secondary nodes are initially aligned, they will always remain aligned. As visualized
in Figure 1, the rotation freedom is a local rotation for each node and not a
global rotation around axis 1-2. Therefore, it is recommended to use a cylindrical joint
with aligned nodes.
Figure 2 shows how a hinge
could be modeled using a cylindrical joint. The cylindrical joint is made of nodes 2, 5,
3 and 4. Note that in hinge modeling nodes must be aligned to get a realistic rotation,
then beams or any other finite elements are used to connect nodes 1-2, 2-5, 4-3 and
nodes 3-6. Finally, it is possible to link nodes 2-3 with a nonlinear elastic spring to
improve the connection.