PSI - Issue 75

5

Fabrice Deleau et al. / Procedia Structural Integrity 75 (2025) 392–418 Emmanuel Persent, Deleau Fabrice, Guillaume Coudouel, Guillaume Perrin/ Structural Integrity Procedia (2025)

396

Soudure. These specific monitoring techniques were applied to gather highly accurate data about the prototype's state. The primary goal was to identify the onset of cracking and stop the fatigue test as soon as it occurred. Both monitoring methods allow the detection of crack initiation, crack propagation, and, of course, the end of the test, which is confirmed by magnetoscopic inspection. The good correlation between all sensors gives us confidence in our diagnosis of crack phenomenon development. These experimental data help to validate our fatigue design methodology.

Nomenclature

min max , F F

Minimum and maximum tensions applied during the cycle

Cauchy stress state at time t

( ) t 

min max ,  

Stress state at minimum and maximum loads

, a m  

Amplitude and mean stress states

Stress range state Duration of cycle Elements of X

 

T

ij X

First invariant of the stress state X

1 ( ) I X 2 ( ) J X

Second deviatoric invariant of the stress state X

Spectral radius of the stress state X

( ) X 

a 

Stress amplitude

 

Stress range Mean stress

m  d  m  P  m a  a  a P  a 

Endurance limit

Mean stress according to (DNV GL RP C203, 2020)

DNV

Proposed mean stress

Stress amplitude according to (API 17G, 2019)

API

Stress amplitude according to (DNV GL RP C203, 2020) Corrected stress amplitude according to (DNV GL RP C203, 2020)

DNV

DNV

Proposed corrected stress amplitude

Mean stress correction factor according to Gerber’s parabola Mean stress correction factor according to (DNV GL RP C203, 2020) Notch support factor according to (DNV GL RP C203, 2020)

G k

m f x f

Material pure alternate endurance limit Material ultimate tensile strength

D 

u 

Von Mises stress Hydrostatic stress

VM  H 



Stress triaxiality factor

N

Number of cycles to failure