Mechanical APDL Basic Analysis Guide

As mentioned earlier, solid-model loads are automatically transferred to the finite element model at
the beginning of solution. If you mix solid model loads with finite-element model loads, couplings, or
constraint equations, you should be aware of the following possible conflicts:

• Transferred solid loads replace nodal or element loads already present, regardless of the order in
  which the loads were input. For example,DL,,,UX on a line overwrites any D,,,UX loads on the nodes
  of that line at transfer time. (DL,,,UX also overwrites D,,,VELX velocity loads and D,,,ACCX acceleration
  loads.)


• Deleting solid model loads also deletes any corresponding finite element loads. For example,
  SFADELE,,,PRES on an area immediately deletes any SFE,,,PRES loads on the elements in that area.


• Line or area symmetry or antisymmetry conditions (DL,,,SYMM,DL,,,ASYM,DA,,,SYMM, or DA,,,ASYM)
  often introduce nodal rotations that could effect nodal constraints, nodal forces, couplings, or constraint
  equations on nodes belonging to constrained lines or areas.

2.5.2. Finite-Element Loads: Advantages and Disadvantages

Advantages:

• There is no need to worry about constraint expansion. You can simply select all desired nodes and specify
  the appropriate constraints.

Disadvantages:

• Any modification of the finite element mesh invalidates the loads, requiring you to delete the previous
  loads and re-apply them on the new mesh.


• Applying loads by graphical picking is inconvenient, unless only a few nodes or elements are involved.

The next few subsections discuss how to apply each category of loads - constraints, forces, surface
loads, body loads, inertia loads, and coupled-field loads - and then explain how to specify load step
options.

2.5.3. DOF Constraints

Table 2.1: DOF Constraints Available in Each Discipline (p. 27) shows the degrees of freedom that can
be constrained in each discipline and the corresponding labels. Any directions implied by the labels
(such as UX, ROTZ, AY, etc.) are in the nodal coordinate system. For a description of different coordinate
systems, see the Modeling and Meshing Guide.

Table 2.2: Commands for DOF Constraints (p. 28) shows the commands to apply, list, and delete DOF
constraints. Notice that you can apply constraints on nodes, keypoints, lines, and areas.

Table 2.1: DOF Constraints Available in Each Discipline

Discipline Degree of Freedom Label

Structural[ 1 ] Translations UX, UY, UZ

Rotations ROTX, ROTY, ROTZ

Hydrostatic Pressure HDSP

Thermal TEMP, TBOT, TE2,...

TTOP

Temperature

Magnetic Vector Potentials AX, AY, AZ

Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

Applying Loads