PD5500 Annex C - Fatigue Assessment

[nco2612]

Gents,

I am looking to understand fatigue assessment to Annex C. We have a calc which determines the principle stresses f1, f2 & f3 based on formulae we have.

What I am looking for is where do these formula come from. I have looked in Bednar & Moss but have not found them.

Principle Stress Formula:

Longitudinal f1 = Kt*p*Ri^2/[(2*Ri+e)*e]
Circumferential f2 = Kt*p*Ri/e
Radial f3 = -0.5*Kt*p

If anyone can shed light on where these are taken from I would be grateful.

 

[DSB123]

nco2612,
The formulae you give are basic formulae for the pressure stresses developed in a cylinder in the longitudinal, circumferential and radial directions. The Kt is an applicable Stress Concentration Factor.