Page 76 - Using ANSYS for Finite Element Analysis A Tutorial for Engineers

stAtIc AnAlysIs usIng Ansys • 63
other externally and internally applied loads. Loads in the ANSYS pro-
gram are divided into six categories: DOF Constraints, Forces, Surface
Loads, Body Loads, Inertia Loads, and Coupled-field Loads.
You can apply most of these loads either on the solid model (key-
points, lines, and areas) or the finite element model (nodes and elements).
For details about the load categories and how they can be applied on your
model, see Loading in this book. Two important load-related terms you
need to know are load step and substep. A load step is simply a config-
uration of loads for which you obtain a solution. In a structural analysis,
for example, you may apply wind loads in one load step and gravity in a
second load step. Load steps are also useful in dividing a transient load
history curve into several segments. Substeps are incremental steps taken
within a load step. You use them mainly for accuracy and convergence
purposes in transient and nonlinear analyses. Substeps are also known as
time steps—steps taken over a period of time.

2.2.2.4 specifying load step options

Load step options are options that you can change from load step to load
step, such as number of substeps, time at the end of a load step, and out-
put controls. Depending on the type of analysis you are doing, load step
options may or may not be required. The analysis procedures in the analy-
sis guide manuals describe the appropriate load step options as necessary.
See Loading for a general description of load step options.

2.2.2.5 initiating the solution

To initiate solution calculations, use either of the following: Command(s):
SOLVE GUI: Main Menu > Solution > Solve > Current LS.
When you issue this command, the ANSYS program takes model
and loading information from the database and calculates the results.
The results are written to the results file (Jobname.RST, Jobname.RTH,
Jobname.RMG, or Jobname.RFL) and also to the database. The only dif-
ference is that only one set of results can reside in the database at one time,
while you can write all sets of results (for all substeps) to the results file.

2.2.3 review the results

Once the solution has been calculated, you can use the ANSYS postpro-
cessors to review the results. Two postprocessors are available: POST1