Split Sleeve Cold Working 2

[WhiteRabbit]

A few years ago there were reports floating around industry about microcracks forming in 7050 series plate in the ST direction when Split Sleeve Coldworking was applied to a hole.

Does anyone know these report numbers?

Did SAE or AIAA have similar reports?

Does anyone else remember this? Everytime I bring this up to someone I get a mystified look.

 

[Stache]

I have installed several thousand sleeves in A-10 aircraft lower wings and I can't remember the engineer name who was head of the porject. However if you contact Tech Support at Wright Patterson AFB they can do some research for you and find the answer I am sure they have helped me several times. They can be reached at:

Tech Suport
1864 4th street
FTE1
AFRL/XPTT
WPFB, OH 45433

1-800-203-6451

Stache

 

[WKTaylor]

Stache..

White rabbit was asking about hole cold working using the split-sleeve-mandrel system [Ah-la Fatugue Technology Inc].

I think You are refering to installation of fastener-sleeves [MIL-DTL-85068/*] for oversize-hole repair using nominal size fasteners.

Boeing has significant restriction on FTI split-sleeve hole cold working [SSCX] in the ST orientation. Reason is as follows...

Ref MMPDS or MIL-HDBK-5 data for 7050 alloy allowables. In the ST orientation "e" can vary from ~10% to ~50% of "e" in the L orientation which are not all that high (~8%-to-12%). This is BAD from the perspective that most cold working requires 3%-to-6% hole expansion just to gain 1%-3% residual (compressive) strain (~increase in hole dia) after CX. Obviously 4% strain on a grain orientation with only 3% strain [at failure], is guaranteed to split (crack) the part on the suseptible grain orientation.... or induce such high residual stresses that it will split (crack) in-service.

Note: Boeing stress engineers are required to use a substantial "knock-down factor" for certain ST calculations involving fasteners [proprietary].

Regards, Wil Taylor