CATIA V5 's solver, ELFINI is a linear solver. So if you have only one load, you can scale your results.
That means:
you computed a max stress of 200 N/mm2 for a load of 1000 N
then for a failure stress of 250 N/mm2 you have to apply X N
X = (1000x250)/200 = 1250 N
You can verify that by...
