Constraints Defined in Local Axis Systems

Constraints can be applied in local axis systems by first defining the system with the command CONSTRUCT COORDSYS, then attaching it to the relevant part with PROPERTY ATTACH COORDSYS and finally applying the constraints.

The local axis system created within FEMGEN is defined in ANSYS input deck by generating three keypoints ('K' command) and writing the ANSYS 'CSKP' command. A node set with all the nodes attached to the present local axis system is generated and these nodes are rotated into the local system with ANSYS 'NROTAT' command. This implies that the degree of freedom directions for each of these nodes are now orientated in the local axis system. The constraints are then specified using the 'D' command. Finally, the global coordinate system is made active with 'CSYS,0', and all the nodes of the model are selected.

Note: if any nodal load is applied to nodes defined in the local axis system, the load should also be defined in the local axis system, see chapter on Load Definition.

Example FEMGEN Commands:

CONSTRUCT COORDSYS RECT CS1      P3       P4       P5     
PROPERTY ATTACH L2   CS1      
PROPERTY BOUNDARY CONSTRAINT CO3  L2  2

Corresponding ANSYS Input Deck:

C*** CONSTRAINTS DEFINED IN LOCAL AXIS SYSTEM 
K, 11, 0.0000000    , 0.0000000    , 0.0000000    
K, 12,  7.071070    ,  7.071070    , 0.0000000    
K, 13,-0.7071068    , 0.7071068    , 0.0000000    
CSKP, 11,0, 11, 12, 13
NSEL,S,NODE,,     1
NSEL,A,NODE,,    18
NSEL,A,NODE,,    35
NSEL,A,NODE,,    68
NSEL,A,NODE,,   101
NROTAT,ALL
D,     1,UY  ,,,,,
D,    18,UY  ,,,,,
D,    35,UY  ,,,,,
D,    68,UY  ,,,,,
D,   101,UY  ,,,,,
CSYS,0
NSEL,ALL