Mechanical APDL Basic Analysis Guide - Ansys

Figure 2.9 Example of Surface Load Gradient
The commands would be as follows:
SFGRAD,PRES,0,Y,0,-25 ! Y slope of -25 in global Cartesian
NSEL,... ! Select nodes for pressure application
SF,ALL,PRES,500 ! Pressure at all selected nodes:
! 500 at Y=0, 250 at Y=10, 0 at Y=20
When specifying the gradient in a cylindrical coordinate system (SLKCN = 1, for example), keep some additional
points in mind. First, SLZER is in degrees, and SLOPE is in units of load/degree. Second, you need
to follow two guidelines:
Guideline 1: Set CSCIR (for controlling the coordinate system singularity location) such that the surface to
be loaded does not cross the coordinate system singularity.
Guideline 2: Choose SLZER to be consistent with the CSCIR setting. That is, SLZER should be between
+180° if the singularity is at 180° [CSCIR,KCN,0], and SLZER should be between 0° and 360° if the singularity
is at 0° [CSCIR,KCN,1].
The following example illustrates why these guidelines are suggested. Consider a semicircle shell as shown
in Figure 2.10 (p. 38), located in a local cylindrical system 11. The shell is to be loaded with an external
tapered pressure, tapering from 400 at -90° to 580 at +90°. By default, the singularity in the cylindrical system
is located at 180°, therefore the θ coordinates of the shell range from -90° to +90°. The following commands
will apply the desired pressure load:
SFGRAD,PRES,11,Y,-90,1 ! Slope the pressure in the theta direction
! of C.S. 11. Specified pressure in effect
! at -90°, tapering at 1 unit per degree
SF,ALL,PRES,400 ! Pressure at all selected nodes:
! 400 at -90°, 490 at 0°, 580 at +90°.
At -90°, the pressure value is 400 (as specified), increasing as θ increases by a slope of 1 unit per degree, to
490 at 0° and 580 at +90°.
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2.5.7. Surface Loads
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