PSI - Issue 59

V. Sidyachenko et al. / Procedia Structural Integrity 59 (2024) 265–270 V. Sidyachenko and V. Pokrovskii / Structural Integrity Procedia 00 (2019) 000 – 000

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β are indicated in parentheses in the figures, respectively. WPS testing was carried out according to a scheme with complete unloading for the mixed mode specimens (Fig. 1b). At the beginning, the specimen was heated above the temperature of the brittle-ductile transition (up to +325 0 C), then loaded to 0.8...0.9 K e – unloaded and cooled, where K e is the equivalent value of the SIF for mixed loading modes by Richard et al. (2017) can be represented as following:

(1)

a

b

Fig. 2. Diagrams of limit states of steels in modes I+II: (a) 15Kh2MFA(II); (b) 10GN2MFA.

After this, the samples were cooled to a temperature of – 100 ° C and fractured at the same mode ratio. The results of calculation the WPS effect on mixed mode fracture toughness are presented in Table 2. The obtained results indicate a greater increase in fracture toughness under mixed mode loading (I+II+III) due to WPS for brittle steel (15Kh2MFA(II)) and a minor effect for ductile (10GN2MFA) steel. See material properties in Table 1.

Table 2. Results of comparative calculations of Ke for mixed I+II+III fracture modes after and without WPS Steel Angles (Fig. 1a) Fracture toughness after WPS , МPа m 1/2 Fracture toughness without WPS K e , МPа m 1/2 Fracture toughness ratio / K e α , 0 β , 0 30 0 132 121.9 1.083 10GN2MFA 60 0 95.1 73.45 1.24 30 30 142.95 128.6 1.111 60 60 97.67 97.5 1.002 30 0 76.76 61.6 1.25 15Kh2MFA(II) 60 0 92.25 74.2 1.24 30 30 71.9 53.47 1.34 60 60 89.4 65.1 1.37

In Fig. 3 temperature dependence of fracture toughness determined as mentioned in Section 2.1 as conventional value of SIF corresponding to the crack initiation is presented. It follows from the given data that WPS under mode II according to the scheme “with total unloading” for steel 15Kh2NМFА(II) at a temperatur e of +20 ° С and -150 ° С does not influence the fracture toughness. Whereas for steel 15Kh2МFА(II) an increase of the fracture toughness by 1.8-fold of the value K IIc at K WPS =100 МPа m 1/2 is observed at a temperature of -150 ° С ( Fig. 3).