STRESS CONCENTRATION UNDER A PIN

[TYL]

I have a fatigue problem at a padeye originally used for installation subsea, now used for tether chains to a buoy. The shackle pin is smaller than the original installation shackle pin. The shackle pin bears on the upper inside surface of the padeye pinhole. The tether chain exerts a set of fatigue tension load ranges on the shackle. I have initially derived the SCF from the Hertz compression stress between the pin and the hole i/d and come up with 7.7, obviously this has given me a rather unattractive fatigue life! Any ideas?

 

[dooron]

Try Roark 6th edn. Art. 7.10 short span beams, compressive stress for short span beams, ratio over bending for l/d=1 is 6, so your number is probably in the ball park.