CONSTRUCT LMASK [lmask] GLOBAL X/Y/Z [INVERSE] Min Max

Next: CONSTRUCT LMASK [lmask] LINE [INVERSE] Umin Up: CONSTRUCT LMASK Previous: CONSTRUCT LMASK [lmask] BODY [INVERSE] Umin

CONSTRUCT LMASK [lmask] GLOBAL X/Y/Z [INVERSE] Min Max

This command is used to define a load mask for use with any load. The load mask is specified in terms of the global X, Y, and/or Z axes. A load mask may be defined in more than one axis by repeating the command with the same load mask name and a different direction. When attached to a load using the command PROPERTY ATTACH the load mask will restrict the action of the load to those nodes or elements which lie within the load mask limits. The INVERSE option may be used to restrict the action of the load to those nodes or elements which lie outside the load mask limits.

A local coordinate system may be attached to the load mask using the command PROPERTY ATTACH. This will modify the load mask location and the orientation of the load mask limits.

lmask	=	name of the load mask
X	=	mask is applied to the global X axis
Y	=	mask is applied to the global Y axis
Z	=	mask is applied to the global Z axis
INVERSE	=	load acts on area outside mask
Min	=	lower limit on axis
Max	=	upper limit on axis

**Figure 2.6:** Definition of a global load mask in the X direction
$\begin{figure} \centerline{ \psfig {figure=diagrams/1dlm1.ps,width=5.0in} }\end{figure}$

**Figure 2.7:** Definition of an inverse global load mask in the X direction
$\begin{figure} \centerline{ \psfig {figure=diagrams/1dlm2.ps,width=5.0in} }\end{figure}$

Notes:

1.: Default names
If no name is entered a default name is created, this is LMn where n is a count of defined load masks. The default name can be changed with the CONSTRUCT NAME command.
2.: Masking criteria
The load mask bases its masking action upon either the coordinates of a node or the centroid of an element or element face. Thus for element loads the mask will simply include or exclude whole elements.
3.: Interaction with space curves
A global load mask will truncate an space curve.
4.: Viewing load masks
The limits of a global load mask can only be viewed by attaching it to a load and using the command LABEL MESH LOAD.

Examples:

1.

CONSTRUCT LMASK LM1 GLOBAL X 23.1 47.6

This creates a load mask which when applied to a line load will restrict the loaded nodes or elements to those whose coordinates lie between x=23.1 and x=47.6.

2.

CONSTRUCT LMASK LM1 GLOBAL X INV 23.1 47.6

This creates a load mask which when applied to a line load will restrict the loaded nodes or elements to those whose coordinates are less than or equal to x=23.1 or greater than or equal to x=47.6.

3.

CONSTRUCT LMASK LM1 GLOBAL X 40 70
CONSTRUCT LMASK LM1 GLOBAL Y 0 90
CONSTRUCT COORDSYS CYL CY1 P5 P6 P2
PROPERTY ATTACH LM1 CY1

This creates a load mask in two of the global directions. A local cylindrical axis system is defined and attached to the load mask changing the X direction to be radial and the Y direction to be rotational.

**Figure 2.8:** Definition of a global load mask with local coordinate system
$\begin{figure} \centerline{ \psfig {figure=diagrams/1dlm3.ps,width=5.0in} }\end{figure}$

See also the following commands

'CONSTRUCT COORDSYS'
'CONSTRUCT NAME'
'CONSTRUCT SCURVE'
'CONSTRUCT TCURVE'
'PROPERTY ATTACH'
'PROPERTY LOAD'
'UTILITY DELETE'
'UTILITY TABULATE'

Next: CONSTRUCT LMASK [lmask] LINE [INVERSE] Umin Up: CONSTRUCT LMASK Previous: CONSTRUCT LMASK [lmask] BODY [INVERSE] Umin

Femsys Limited
1st October 1999