PSI - Issue 41

Hendrik Baarssen et al. / Procedia Structural Integrity 41 (2022) 183–191

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Baarsen et al. / Structural Integrity Procedia 00 (2022) 000–000

(a) Specimen geome try, in mm

(b) Specimen clamped in testing machine (c) Location of strain gauges and COD-meter installed on knife-edges

Fig. 1: Specimen geometry and test setup

Brittle fracture

Assessment point

Failure locus

Load line

Plastic collapse

Fig. 2: The failure assessment diagram

of the specimen, the load type, and the size of the crack at failure, as found on the fracture surface of the specimens. In particular it turned out that cracks were essentially of two types: (1) through the thickness cracks, and (2) corner cracks at the hole. The stress intensity factor formula used are those reported in BSI (2013). The material fracture toughness in terms of stress intensity factor including constraint correction, K c mat , is estimated through correlation with the Charpy impact energy, using the Master Curve. In particular: K mat = 20 + { 11 + 77 exp[0 . 019( T − T 0 − T k )] } 25 B 1 2 ln 1 1 − P f 1 4 (4) where T is the temperature at which K mat is to be determined, T 0 = T 27 J − 18 is the temperature for a median toughness of 100 MPa √ m in 25 mm thick specimens, T k = 25 describes the scatter in the Charpy vs fracture toughness correlation, B is the thickness for which an estimation of the toughness is required, and P f is the probability of K mat being less than estimated. Once K mat is estimated, the value including allowance for constraint correction, i.e. for