PSI - Issue 75

11

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

402

• Notch support factor Additionally, a geometrical correction coefficient

x f linked to the welding manufacturing is added by (DNV GL RP

C203, 2020). This factor is linked to the welding notch radius r , and is expressed in equation (11):

1.37

if if

1mm

r

    



( ) 0.136 1 log( ) r −

10

1mm 10mm r

f

=

  

(11)

x

1.0

i

f

10 m m

r

As it could be very challenging to define a notch radius, a notch support factor of 1

x f = will be used for the i-Clip

connector, this corresponding to the conservative assumption.

• Corrected stress amplitude The final stress amplitude DNV

a  , which shall be used for estimating the lifetime, is obtained from DNV

a  described in

equation (5), multiplied by the mean stress correction factor

m f given in equation (7) and divided by the notch support

coefficient

x f presented in equation (11). It is shown in equation (12):

f

(12)

a



=



m a

DNV

DNV

f

x

2.5. Proposed fatigue analysis methodology The numerical simulation verified that the stress evolution is stabilized (adapted stress state) during the dynamic solicitation. Material plasticity occurred close to the hot spot zone and affected the average stress value. • Calculating the stress amplitude The stress amplitude is calculated in the same way as in the (DNV GL RP C203, 2020) method, in equation (6). • Mean stress correction The influence of the mean stress on the fatigue lifetime is introduced with Gerber’s parabola (Budynas et al., 2014), because its nonlinear effect is proven in uniaxial load, according to (Gaur, 2016). The parabolic expression is given in equation (13) for a pure alternate endurance limit D  and an ultimate tensile strength u  : 2 1 a m D u     + =       (13) This aspect can be translated to a correction factor G k applied to the stress amplitude, given in equation (14):

1

(14)

k

=

G

2

m       u  

1

−

m  will be set equal to

m P  , which is given in equation (19).

Where

• Calculating the mean stress The present paper proposes the use of a different mean stress as presented previously. For an equi-bitension stress