PSI - Issue 59

Viktor Kovalov et al. / Procedia Structural Integrity 59 (2024) 771–778

776

6

V. Kovalov et al. / Structural Integrity Procedia 00 (2019) 000 – 000

(10)

After potentisation we obtain:

(11)

or

(12)

The obtained equation (12) characterises the fatigue crack growth rate depending on the change in the stress intensity factor during cyclic loading of samples from 40X steel cooled after annealing in a heat-insulating mixture. The results of experimental studies and corresponding calculations are given in Table 1.

Table 1. Experimental data and elements of fatigue crack growth rate calculation. № sample ΔK da , mm dN , cycle mm/cycle

lg (ΔK)

l i , mm

For model samples from steel 40 cooled after annealing in a heat-insulating mixture

26.938387 28.1344427 85.40154 35.063007 58.087932 48.462428 39.605972 37.060051

0.6 0.7 2.3 0.4

18000 28000 20000 8000 21000 9000 42000 26000

0.000033 0.000025 0.000115 0.00005

1.4303 1.4492 1.9314 1.5448

-4.4771 -4.6021 -3.9393 -4.301 -4.0212 -3.9542 -4.6232 -4.4150

23.6 24.3 25.3 25.7

1

2

For model samples from 40X steel cooled after annealing in a heat-insulating mixture

2 1 1 1

0.0000952 0.00011111 0.00002381 0.0000385

1.76408592 1.68540517 1.59776068 1.56890601

30 31 30 31

1

2

For steel 40 specimens cooled after heat treatment in air, the following equation is obtained:

(13)

or

.

(14)

After potentisation we obtain:

(15)

or

.

(16)

Similarly for 40X steel specimens that have undergone heat treatment with air cooling:

(17)

or

.

(18)