PSI - Issue 17

Grzegorz Lesiuk et al. / Procedia Structural Integrity 17 (2019) 198–205 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

201

4

ˆ ( ( )) d v F d v F ˆ ( ( )) Q

ˆ ( ) L v F

=

L

(for F=F k )

(4)

dF

dF

According to the above conditions, we obtain:

k k B B F B F A A F B B F A A F 1 0 2 2 1 0 1 0 2 1 2 + + = + = + + k k

(5)

k

The constants B 0 , B 1 , B 2 should be optimal from the mathematical point of view. In order to obtain their optimal values, we can find the mentioned constants by minimalizing the residual sum of squares  (RSS) defined as:

2 v F v for P P v F v for P P −  −  2 ˆ ( ( ) ) ( ( ) ) Q i i L i i ˆ i i k k

  

  

1

N 



=



.

(6)

2

max COD COD − (

)

i

1

=

min

Fig. 2. The schematic idea of the closure load estimation

Fig. 3.  K-kinetic fatigue fracture diagram for tested puddle iron