Fatigue Properties of 2024-T42 Clad Sheet

[SAITAETGrad]

Does anyone know of a reference for fatigue data (S-N curves, Goodman diagrams, etc.) for 2024-T42 clad sheet?

Alternately, can anyone comment on the comparitive fatigue performance of 2024-T42 clad sheet and 2024-T3 clad sheet? The static strength is higher but the hardness lower for -T42. Overall, I'm assuming that the fatigue properties of -T42 are lesser as -T3 is much more commonly used for fatigue critical applications.

 

[rb1957]

i'd use the MIl HDBK 5 (or AR-MMPDS-01) s/n curves for 2024T4. If i was nervous about the installation I'd use 10% higher stress (to allow for the cladding, approx. 10% of the thickness).

 

[40818]

Again, as per RB1957's reply.

Need look no further than Mil-Hdbk-5 and/or MMPDS.

You can carry out some simple comparative fatigue checks for each material and see the differences.
When i visualise fatigue comparisons by eye, i always think that bendy/flexible materials are better than stiff materials. Just the way i think about it.
What application are you going to use the materials in?

 

[SAITAETGrad]

First, thank you for responding.

Naturally MMPDS was the first place I looked but the T4 curves are for thicker stock than sheet and the curves for T3 are all sheet...

My understanding is that thickness is a factor in fracture toughness...so would there really be a basis of comparison?

Flexible materials better in fatigue...yes. I don't disagree with what you are saying and I can see how your experience may bouy your confidence, but for myself, I think I'll need a bit more information/understanding before
proceeding to presentation, approval, and installation based on this loose method.

The material is an existing aircraft pressurized skin.

 

[rb1957]

thickness affects the fracture mode but has little effect on fatigue properties. The curves are the best information you're likely to get. if you feel uncomfortable with them, add in an analysis uncertainty factor (2?, ie 1/2 the curve life, whcih equates to about a 10% increase in stress).

 

[40818]

If memory serves me right, and i'm 2 glasses into a bottle of chardonney, i think fuchs and stevens book (Metal Fatigue in Engineering) gives "monotonic and cyclic strain properties of materials" somewhere at the back end of it.

If your talking about aircraft pressure skins, the skin and frames carry the hoop tension loads in about an 80-85%/15-20% proportions. Depending on the aircraft type?? You would end up with anwhere between 10-18Ksi hoop tension.
But the fatigue requirements of each aircraft type should be defined by the oem.