Constraints

RADIOSS supports several different kinematic constraints, which are mainly used to impose acceleration, velocity, displacement or temperature in structure or constraint the moving of structure. They are mutually exclusive for each degree-of-freedom (DOF). Two kinematic conditions applied to the same node may be incompatible.

Groups	Keywords	Application	Description
Rigid Bodies	/RBE2	Rigid element	Defines a rigid body whose independent degrees-of-freedom are specified at a single grid point and whose dependent degrees-of-freedom are specified at an arbitrary number of grid points.
	/RBODY	Spotwelds, moving or fixed rigid body, rigid boundary	One master node and its associated slave nodes to describe structure with mass and inertia.
	/RBODY/LAGMUL	Spotwelds, moving or fixed rigid body, rigid boundary	One master node and its associated slave nodes using Lagrange multiplier method.
Boundary Conditions and Constraints	/BCS	Boundary condition	Boundary conditions on node groups for translational and rotational motion.
	/BCS/LAGMUL	Boundary condition	Boundary conditions on node groups for translational and rotational motion with Lagrange multiplier method.
	/IMPACC	Move structure with specified acceleration	Imposed accelerations on a group of nodes.
	/IMPDISP	Move structure with specified displacement	Imposed displacement on a group of nodes.
	/IMPDISP/FGEO	Position nodes to reference geometry in Airbag simulation	A displacement is imposed to node from its initial position to final position.
	/IMPTEMP	Heat source	Imposed displacement on a group of nodes.
	/IMPVEL	Move structure with specified velocity	Imposed velocity on a group of nodes.
	/IMPVEL/FGEO	Position nodes to reference geometry in Airbag simulation	A velocity is imposed to node from its initial position to final position.
	/IMPVEL/LAGMUL	Move structure with specified velocity	Imposed velocity on a group of nodes with Lagrange multiplier method.
Rigid Link	/RLINK	Infinite stiff spring	Imposes the same velocity on all the slave nodes in one or more directions.
Rigid Walls	/RWALL/LAGMUL	Fixed or moving rigid barrier	Infinite Plane rigid wall with Lagrange multiplier method.
Rigid Walls	/RWALL	Fixed or moving rigid barrier	Infinite Plane, Infinite Cylinder, Sphere and Parallelogram rigid wall.
Joints	/CYL_JOINT	Hinge (like door hinge)	A cylindrical joint is like a rigid body but without master node. A kinetic condition is applied on all slave nodes.
Joints	/GJOINT	Complex (gear-type) joints	Set specific kinematic relations to represent gear kinematics, which are treated by a global Lagrange multiplier solver.
Tied Contact	/INTER/TYPE2	Model connection like spotwelds and rivets	Tied Connection between two Lagrangian materials.
Flexible Body	/FXBODY	Eigen analysis on a complete truck	Flexible Body
Constraints	/MPC	Gear type joints	Apply multi-point constraints on nodes.
Constraints	/RBE3	Rigid element	Defines the motion at a "reference" grid point as the weighted average of the motions at a set of other grid points.

Constraints

Constraints

Constraints

Rigid Bodies

Rigid element

Defines a rigid body whose independent degrees-of-freedom are specified at a single grid point and whose dependent degrees-of-freedom are specified at an arbitrary number of grid points.

Spotwelds, moving or fixed rigid body, rigid boundary

One master node and its associated slave nodes to describe structure with mass and inertia.

Spotwelds, moving or fixed rigid body, rigid boundary

One master node and its associated slave nodes using Lagrange multiplier method.

Boundary Conditions and Constraints

Boundary condition

Boundary conditions on node groups for translational and rotational motion.

Boundary condition

Boundary conditions on node groups for translational and rotational motion with Lagrange multiplier method.

Move structure with specified acceleration

Imposed accelerations on a group of nodes.

Move structure with specified displacement

Imposed displacement on a group of nodes.

Position nodes to reference geometry in Airbag simulation

A displacement is imposed to node from its initial position to final position.

Heat source

Imposed displacement on a group of nodes.

Move structure with specified velocity

Imposed velocity on a group of nodes.

Position nodes to reference geometry in Airbag simulation

A velocity is imposed to node from its initial position to final position.

Move structure with specified velocity

Imposed velocity on a group of nodes with Lagrange multiplier method.

Rigid Link

Infinite stiff spring

Rigid Walls

Fixed or moving rigid barrier

Fixed or moving rigid barrier

Infinite Plane, Infinite Cylinder, Sphere and Parallelogram rigid wall.

Joints

Hinge (like door hinge)

A cylindrical joint is like a rigid body but without master node. A kinetic condition is applied on all slave nodes.

Complex (gear-type) joints

Set specific kinematic relations to represent gear kinematics, which are treated by a global Lagrange multiplier solver.

Tied Contact

Model connection like spotwelds and rivets

Tied Connection between two Lagrangian materials.

Flexible Body

Eigen analysis on a complete truck

Flexible Body

Constraints

Gear type joints

Apply multi-point constraints on nodes.

Rigid element

Defines the motion at a "reference" grid point as the weighted average of the motions at a set of other grid points.