PSI - Issue 7

4

Mirco D. Chapetti/ Structural Integrity Procedia 00 (2017) 000–000

Mirco D. Chapetti / Procedia Structural Integrity 7 (2017) 229–234

232

∆ K dR

B H V

A

Lower bound

d π

Fig. 3. Schematical representation of expression (6).

H d π Fig. 4 plots a set of data published by Kunio et al (1979) and Kunio et al (1984), for which the following expression can be obtained with good results for low and medium strength (ferritic-pearlitic and martensitic) steels and load ratio R = -1: (7) All data used to obtain the results showed in Fig. 3 are listed in Table 1. SXXC steels are mainly included (10C, 20C, 35C and 55C), with ferriti-pearlitic and martensitic microstructures. K 1 0.5 ∆ = + V dR

5

0 ∆ K dR Experimetal, MPa m 1/2 1 2 3 4

0

1

2

3

4

5

∆ K dR Estimated, MPa m 1/2

Fig. 4. Experimetal vs . estimated ∆ K dR for steels.