/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) (6) (7) (8) (9) (10)
/RBE2/rbe2_ID
rbe2_title
node_ID Trarotref Skew_ID grnd_ID Iflag

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)
Trarotref 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)
Iflag 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
TX TY TZ ω X ω Y ω Z

Definition

Field Contents SI Unit Example
TX Code for translation TX.
=0
free DOF
=1
fixed DOF

(Boolean)
TY Code for translation TY.
=0
free DOF
=1
fixed DOF

(Boolean)
TZ Code for translation TZ.
=0
free DOF
=1
fixed DOF

(Boolean)
ω X Code for rotation ω X .
=0
free DOF
=1
fixed DOF

(Boolean)
ω Y Code for rotation ω Y .
=0
free DOF
=1
fixed DOF

(Boolean)
ω Z Code for rotation ω Z .
=0
free DOF
=1
fixed DOF

(Boolean)

Comments

  1. Two formulations of dependent motion are available in Iflag:

    If Iflag=0

    u ˙ s ( dependent translation ) = [ T r a ] ( u ˙ m + D ˙ s m ⊗ θ ˙ m ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabCyDayaaca WaaSbaaSqaaiaadohaaeqaaOWaaeWaaeaaqaaaaaaaaaWdbiaabsga caqGLbGaaeiCaiaabwgacaqGUbGaaeizaiaabwgacaqGUbGaaeiDai aabckapaGaaeiDaiaabkhacaqGHbGaaeOBaiaabohacaqGSbGaaeyy aiaabshacaqGPbGaae4Baiaab6gaaiaawIcacaGLPaaacqGH9aqpda WadaqaaiaadsfacaWGYbGaamyyaaGaay5waiaaw2faamaabmaabaGa bCyDayaacaWaaSbaaSqaaiaad2gaaeqaaOGaey4kaSIabCirayaaca WaaSbaaSqaaiaadohacaWGTbaabeaakiabgEPielqahI7agaGaamaa BaaaleaacaWGTbaabeaaaOGaayjkaiaawMcaaaaa@5F65@
    θ ˙ s ( r o t a t i o n ) = [ R o t ] θ ˙ m

    If Iflag=1

    u ˙ s ( t r a n s l a t i o n ) = [ T r a ] u ˙ m + D ˙ s m ⊗ [ R o t ] θ ˙ m
    θ ¯ s ( r o t a t i o n ) = [ R o t ] θ ¯ m
    [ T r a ] , [ R o t ] = [ i 0 0 0 j 0 0 0 k ]

    With i , j , k =0,1

    The default formulation Iflag =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 Trarotref 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 Trarotref is applied on independent node, this formulation is used prior to version 10.0.5.

  2. 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.
  3. 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.
  4. Hierarchy rule involving /INTER/TYPE2, /RBE2, /RBE3 and /RBODY is:

    RBODY > RBE3 > RBE2 > INTERFACE TYPE2

  5. 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.
  6. The RBE2 uses a scalar inertia calculation similar to using /RBODY with Ispher=1.