/RBE2

Block Format Keyword Defines a rigid body whose independent degrees of freedom are specified at a single independent node and whose dependent degrees of freedom are specified at an arbitrary number of dependent nodes.

Format

(1)	(2)	(3)	(4)	(5)
/RBE2/`rbe2_ID`
`rbe2_title`
`node_ID`	`Trarot`_ref	`Skew_ID`	`grnd_ID`	`I`_flag

Definition

Field	Contents	SI Unit Example
`rbe2_ID`	Rigid element identifier. (Integer, maximum 10 digits)
`rbe2_title`	Rigid element title. (Character, maximum 100 characters)
`node_ID`	Independent node identifier. (Integer)
`Trarot`_ref	Code of DOF used for the dependent components. =0 free DOF =1 fixed DOF (6 Booleans) Default (blank or 6 zeros) set on all DOF
`Skew_ID`	Local skew identifier of element. (Integer)
`grnd_ID`	Dependent nodes group identifier. (Integer)
`I`_flag	Dependent relation formulation flag. 1 = 0 (Default) Rigid body formulation (OptiStruct) = 1 Rigid link formulation (Integer)

Codes for Translation and Rotation: `Trarot`

(1)-1	(1)-2	(1)-3	(1)-4	(1)-5	(1)-6	(1)-7	(1)-8	(1)-9	(1)-10
			`T`_X	`T`_Y	`T`_Z		$ω_{X}$ $ω_{X}$	$ω_{Y}$ $ω_{Y}$	$ω_{Z}$ $ω_{Z}$

Definition

Field	Contents	SI Unit Example
`T`_X	Code for translation `T`_X. =0 free DOF =1 fixed DOF (Boolean)
`T`_Y	Code for translation `T`_Y. =0 free DOF =1 fixed DOF (Boolean)
`T`_Z	Code for translation `T`_Z. =0 free DOF =1 fixed DOF (Boolean)
$ω_{X}$ $ω_{X}$	Code for rotation $ω_{X}$ $ω_{X}$ . =0 free DOF =1 fixed DOF (Boolean)
$ω_{Y}$ $ω_{Y}$	Code for rotation $ω_{Y}$ $ω_{Y}$ . =0 free DOF =1 fixed DOF (Boolean)
$ω_{Z}$ $ω_{Z}$	Code for rotation $ω_{Z}$ $ω_{Z}$ . =0 free DOF =1 fixed DOF (Boolean)

Comments

Two formulations of dependent motion are available in I_flag:
If Iflag=0(1)
${˙ u}_{s} (dependent translation) = [T r a] ({˙ u}_{m} + {˙ D}_{s m} \otimes {˙ θ}_{m})$ ${\dot{u}}_{s} (dependent translation) = [T r a] ({\dot{u}}_{m} + {\dot{D}}_{s m} \otimes {\dot{θ}}_{m})$
(2)
${˙ θ}_{s} (r o t a t i o n) = [R o t] {˙ θ}_{m}$ ${\dot{θ}}_{s} (r o t a t i o n) = [R o t] {\dot{θ}}_{m}$

If Iflag=1(3)
${˙ u}_{s} (t r a n s l a t i o n) = [T r a] {˙ u}_{m} + {˙ D}_{s m} \otimes [R o t] {˙ θ}_{m}$ ${\dot{u}}_{s} (t r a n s l a t i o n) = [T r a] {\dot{u}}_{m} + {\dot{D}}_{s m} \otimes [R o t] {\dot{θ}}_{m}$
(4)
${¯ θ}_{s} (r o t a t i o n) = [R o t] {¯ θ}_{m}$ ${\bar{θ}}_{s} (r o t a t i o n) = [R o t] {\bar{θ}}_{m}$
(5)
$[T r a], [R o t] = [\begin{matrix} i & 0 & 0 \\ 0 & j & 0 \\ 0 & 0 & k \end{matrix}]$

With $i$ , $j$ , $k$ =0,1

The default formulation I_flag =0 corresponds to OptiStruct's RBE2, in which the motion of a group of dependent nodes depends on the motion of one independent node which always has 6 DOF. The input Trarot_ref is applied on the dependent nodes and the element behaves like a rigid body.

The second formulation is similar to /RLINK; but takes into account the equilibrium between translations and rotations. The input Trarot_ref is applied on independent node, this formulation is used prior to version 10.0.5.
A independent node can be attached to a finite element. The independent node can also be defined in a different RBE2 as independent node and/or dependent node, but the dependent node cannot have the incompatible kinematic conditions.
It is not recommended for dependent or independent nodes of an /RBE2 to also be dependent or independent nodes in another constraint equation (kinematic conditions). However, this is permitted if the hierarchy rule has been respected: RBE2 should have a higher level than Interface TYPE2 (independent nodes of Interface TYPE2 can be dependent node of RBE2); but a lower level than RBE3 and RBODY. The hierarchy between different RBE2s is allowed, re-ordering will be done automatically to determine the hierarchy by Radioss Starter, if hierarchy levels between RBE2 are too high, error will be printed out.
Hierarchy rule involving /INTER/TYPE2, /RBE2, /RBE3 and /RBODY is:
RBODY > RBE3 > RBE2 > INTERFACE TYPE2
More output messages could be obtained using Ipri of /IOFLAG: Ipri > 3 will printout new mass and inertia of the independent nodes; Ipri > 5 will printout the new RBE2 identifier and hierarchy level after re-ordering.
The RBE2 uses a scalar inertia calculation similar to using /RBODY with I_spher=1.

/RBE2

Format

Definition

Codes for Translation and Rotation: Trarot

Definition

Comments

Codes for Translation and Rotation: `Trarot`