In a clean working directory, start Pre & Post or MSC.Patran and import the model and results using the MSC.Nastran results file simpleSN.op2 into a new database called load_spec.

Open the Main MSC.Fatigue form and set Analysis to S-N, Results Loc. to Node, Node Ave. to Global, F.E. Results to Stress, Res. Units to MPa, Jobname to load_spec, and Title to Load Spectrum Analysis.

Open the Solution Params form and verify that the Mean Stress Correction is set to None and that the Stress Combination is set to Max. Abs. Principal. Click OK to accept the inputs.

Open the Material Info form and set Material to MANTEN_MSN, set Finish to No Finish, set Treatment to No Treatment, and set Region to default_group. Click OK to accept the inputs.

The Aerospace Loading capability is invoked by setting the Job Setup for widget to Load Spectrum. Note the absence of the reference to the load time history database as this is not required for handling aerospace spectrum files. Instead there are two navigation bars pointing to the location of the Spectrum and Load Case files. See the form below:

Users can browse to the directories containing these files and edit the files to create their own Spectrum and Load Control files. The example Load Control and Spectrum files are shown below. Stresses for the 2 FE- Cases are read from the Patran database.

Note that in the given example, the same FE case is selected twice. This is because at least two FE cases must be used for the Aerospace Loading capability. Since the stress due to a fully reversed load is to be modeled, the FE case is scaled first by +1.0, and then by -1.0.

QSG Sample Load File 
N
3
2
1.0,1.0

0,Load 0, 0.0,0.0
1,load +1, 1.0, 0.0
2,load -1, 0.0, -1.0              

SPECTRUM FILE V2
QSG Sample Spectrum File
1
1
1
1

Flight, 1,1,1
Block1,1, 0,1,2,0

Open the Job Control form. Set the Action to Full Analysis and click Apply. When the job is completed open the Results form on the main MSC.Fatigue setup form and set the Action to Read Results. Click Apply. This will read the results into the database. The Log of damage, together with the stress time history at node 1 is identical to the example in Chapter 2 of the Quick Start Guide.

Exercise: Change the number of repeats for the flight in the spectrum file to 2 and compare the results with the above. Damage at Node 1 should double. The individual event (Block 1) may also be repeated to obtain the same result.