Mechanical APDL Basic Analysis Guide - Ansys

Chapter 2: Loading
Changing the value of BFK, BFL, BFA, or BFV constraints between solutions may produce many of these
warnings at the 2nd or later solid BC transfer. These can be prevented if you delete the nodal BF loads
between solutions using BFVDELE, BFADELE, BFLDELE, and/or BFDELE.
2.5.9. Applying Inertia Loads
Use the following commands for inertia loads:
Table 2.9 Inertia Loads Commands
ACEL
CGLOC
CGOMGA
Command
CMDOMEGA
CMOMEGA
DCGOMG
DOMEGA
IRLF
OMEGA
There are no specific commands to list or delete inertia loads. To list them, issue STAT, INRTIA. To remove
an inertia load, set the load value to zero. You can set an inertia load to zero, but you cannot delete it. For
ramped load steps, inertia loads are ramped to zero. (This is also true when you apply inertia loads.)
The ACEL, OMEGA, and DOMEGA commands specify acceleration, angular velocity, and angular acceleration,
respectively, in global Cartesian directions.
Note
The ACEL command applies an acceleration field (not gravity) to a body. Therefore, to apply
gravity to act in the negative Y direction, you should specify a positive Y acceleration.
Use the CGOMGA and DCGOMG commands to specify angular velocity and angular acceleration of a spinning
body which is itself revolving about another reference coordinate system. The CGLOC command specifies
the location of the reference system with respect to the global Cartesian origin. You can use these commands,
for example, to include Coriolis effects in a static analysis.
You can also use the CMOMEGA and CMDOMEGA commands to specify the rotational velocity and acceleration
effects for element components you define. You either specify an axis and the scalar vector quantity,
or define the three components of the rotational value and the point in space you are considering. You can
use these commands for Element components only.
Inertia loads are effective only if your model has some mass, which is usually supplied by a density specification.
(You can also supply mass to the model by using mass elements, such as MASS21, but density is more
commonly used and is more convenient.) As with all other data, the ANSYS program requires you to use
consistent units for mass. If you are accustomed to the U. S. Customary system of units, you might sometimes
wish to use weight density (lb/in 3 ) instead of mass density (lb-sec 2 /in/in 3 ), for convenience.
Use weight density in place of mass density only under these conditions:
• The model will only be used in a static analysis.
• No angular velocity or angular acceleration is applied.
• Gravitational acceleration is unity (g = 1.0).
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