In GasTurb, if you select More (...than Performance) in the program main window, then you can calculate for many engine configurations the basic geometry of the gas turbine including the disks and their stresses. The shape of the disk can be adapted in such a way that the design margin is equal to a specified value, expressed in percent. A numerical optimization routine allows to optimize the geometry of disks automatically.
The disk design can be done as part of the preliminary design within GasTurb or one can deal with each of the disks separately employing GasTurb Details and feed back the results into the cycle program. GasTurb Details has a much more detailed disk design output than GasTurb.
The stresses in the disk and the design margins depend on the material used for manufacturing the disk. The program comes with a material data base which contains information from open literature. The material data base is a pure ASCII file which can be edited from within GasTurb Details or modified with any other text editor.