5754 - how far above yield/proof 1

[scander]

We have an aluminium wall that is meant to withstand a pressure load of ~160MPa, total of around 1000 cycles in its lifetime. Originally the idea was to go with 6082 T6 and thus be able to remain below the yield/proof stress (220-250 for the T6). However, the part needs to be bent and during reviewing we realized 6082 is in principle avoided for bending and instead the suggestion of using 5754 H22 was made.

Now 5754 is fine for bending but has a much lower proof strength of Rp0.2 = 130MPa. In such materials/alloys, it is unclear to me what is the exact behaviour of the alloy over the proof strength. In particular, how many times and by how much could we operate at the expected +30MPa over the Rp0.2? How much of a plastic deformation is added with every cycle? Is this something that can be calculated or I am looking at a completely different alloy or strengthening of the geometry?

Thanks

 

[realtime2]

Some fatigue curves for 5754 are
located here:

http://fde.uwaterloo.ca/Fde/Materials/Alum/AA5xxx/aa5xxx.html