Mechanical APDL Basic Analysis Guide - Ansys

Chapter 2: Loading
Figure 2.10 Tapered Load on a Cylindrical Shell
You might be tempted to use 270°, instead of -90°, for SLZER:
SFGRAD,PRES,11,Y,270,1 ! Slope the pressure in the theta direction
! of C.S. 11. Specified pressure in effect
! at 270°, tapering at 1 unit per degree
SF,ALL,PRES,400 ! Pressure at all selected nodes:
! 400 at -90°, 490 at 0°, 580 at +90°
However, as shown on the left in Figure 2.11 (p. 38), this will result in a tapered load much different than
intended. This is because the singularity is still located at 180° (the θ coordinates still range from -90° to
+90°), but SLZER is not between -180° and +180°. As a result, the program will use a load value of 400 at
270°, and a slope of 1 unit per degree to calculate the applied load values of 220 at +90°, 130 at 0°, and 40
at -90°. You can avoid this behavior by following the second guideline, that is, choosing SLZER to be between
±180° when the singularity is at 180°, and between 0° and 360° when the singularity is at 0°.
Figure 2.11 Violation of Guideline 2 (left) and Guideline 1 (right)
220
+90°
y
11 x
310 +180°
0° 130
-90°
+270°
40
400
310
+180°
220
+90°
y
11
+270°
400
x
0°
+360°
singularity
130
490
Suppose that you change the singularity location to 0°, thereby satisfying the second guideline (270° is then
between 0° and 360°). But then the θ coordinates of the nodes range from 0° to +90° for the upper half of
38
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