PSI - Issue 33

Saki Hayashi et al. / Procedia Structural Integrity 33 (2021) 1162–1172 Hayashi et al / Structural Integrity Procedia 00 (2019) 000 – 000

1170

9

Y i ( T , t , Sn) was approximated as a function proportional to a normal distribution function with t and Sn fixed and T as a variable, and the parameters describing normal distribution function, mean μ , standard deviation σ , and proportionality constant, K ( t , Sn), were fitted by the least-squares method. ( , , ) = ( , ) ∗ √ 1 2 − 1 2 ( − ( ) ) 2 (11) ( ) = ∗ ln + (12) ( , ) = ∗ ln + ( ) (13) ( ) = ∗ + (14) ･ Completion of Eq.(7) Finally, the proportionality constant C (t) of Y i ( T , t , Sn) was obtained by fitting C for t = 5, 50, 500, and 5000 and fitting the result to C as C is a linear function of t . ( ) = ∗ ln + (15) The values of the parameters obtained by calculation are summarized in Table 2.

Fig. 12. The flowchart of the model configuration.

Table 2. Coefficients of the model (for B free steel). Parameter

2.96 × 10 −4 8.58 × 10 −1 −2.31 × 10 1.44 × 10 2 −1.74 × 10 8.07 × 10 2 8.49 × 10

Coefficient determined by LSM

A B

a b

C(t) ( ) ( , )

8.00 ( ) c 5.39 × 10 4 d 8.71