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 the shell, and 270° to 360° for the lower half. The surface to be loaded crosses the singu-
larity, a violation of Guideline 1:
CSCIR,11,1! Change singularity to 0°
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 270°, 490 at 360°, 220 at +90°
! and 130 at 0°Again, the program uses a load value of 400 at 270° and a slope of 1 unit per degree to calculate the
applied load values of 400 at 270°, 490 at 360°, 220 at 90°, and 130 at 0°.Violating Guideline 1 cause a
singularity in the tapered load itself, as shown on the right in Figure 2.11:Violation of Guideline 2 (left)
and Guideline 1 (right) (p. 38). Due to node discretization, the actual load applied not change as abruptly
at the singularity as it is shown in the figure. Instead, the node at 0° have the load value of, in the case
shown, 130, while the next node clockwise (say, at 358°) have a value of 488.
The SFGRAD specification stays active for all subsequent load application commands. To remove the
specification, simply issue SFGRAD without any arguments. Also, if an SFGRAD specification is active
when a load step file is read, the program erases the specification before reading the file.
Large-deflection effects can change the node locations significantly. The SFGRAD slope and load value
calculations, which are based on node locations, are not updated to account for these changes. If you
need this capability, use SURF153 with face 3 loading or SURF154 with face 4 loading.
2.5.7.4. Repeating a Surface Load
By default, if you repeat a surface load at the same surface, the new specification replaces the previous
one. You can change this default to add (for accumulation) or ignore using one of the following:
Command(s):SFCUM
GUI: Main Menu> Preprocessor> Loads> Define Loads> Settings> Replace vs. Add> Surface Loads
Main Menu> Solution> Define Loads> Settings> Replace vs. Add> Surface Loads
Any surface load you set stays set until you issue another SFCUM command. To reset the default setting
(replacement), simply issue SFCUM without any arguments. The SFSCALE command allows you to scale
existing surface load values. Both SFCUM and SFSCALE act only on the selected set of elements. The
Lab field allows you to choose the surface load label.
2.5.7.5. Transferring Surface Loads
To transfer surface loads that have been applied to the solid model to the corresponding finite element
model, use one of the following:
Command(s):SFTRAN
GUI: Main Menu> Preprocessor> Loads> Define Loads> Operate> Transfer to FE> Surface Loads
Main Menu> Solution> Define Loads> Operate> Transfer to FE> Surface Loads
To transfer all solid model boundary conditions, use the SBCTRAN command. (See DOF Constraints (p. 27)
for a description of DOF constraints.)
2.5.7.6. Using Surface Effect Elements to Apply Loads
Occasionally, you may need to apply a surface load that the element type you are using does not accept.
For example, you may need to apply uniform tangential (or any non-normal or directed) pressures on
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationApplying Loads