PSI - Issue 14

Filin V.Yu. et al. / Procedia Structural Integrity 14 (2019) 758–773 Filin V.Yu, Ilyin A.V. / Structural Integrity Procedia 00 (2018) 000–000

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and SENT specimens need a load P vs. crack mouth opening displacement (CMOD) record obtained with the help of clip-on gauges. In some cases two gauges installed at different height from specimen surface are applied. CTOD is usually found as a sum of its elastic and plastic components. The elastic component is related to the load in terms of K 1 while the plastic one is derived from the plastic part of CMOD v pl using the “center of rotation” assumption. E.g. for deep-notched SENB specimen,   0 pl 0 2 2 1 0.4 0.6 )v 0.4( / 1 W a W a E K        . (29) Validity of test results relates to the following conditions:  An observance of precracking conditions (no overloading),  An observance of specimen geometry and crack shape,  Sampling by a crack of the target structural area of welded joints,  The maximum values related to the restrictions of EPFM, assuming B is the minimum specimen dimension, / 20 max Y B J   , / 33 max B   . (30) Note: even these restrictions allow to widen ( K c ) J range in comparison with K Ic in ten times. If the experimentally found values exceed the maximum ones as per (29), they should be restricted at statistical interpretation. When all the experimental data are above the maximum ones, it is likely that a high stable crack extension is observed during the test. When the maximum loads plateau is attained without pop-ins or sudden fracture at the temperature corresponding to an assessment case, no additional calculations are needed to prove the material strength in respect of cleavage fracture. Issues related to experimental data that are solved in the developed procedure are discussed below.

3.4 Choice of specimen size and type

Loading mode and specimen geometry have a great effect on cleavage fracture resistance. This constraint effect was described in terms of parameter Q by O’Dowd and Shih (1991) accounting for stress field deviation for a certain specimen from HRR solution ij ij ij Q       Y HRR ( ) . (31)

Figure 5 – Specimen types. Size B  0.8 S , colour symbols are referenced in Fig. 6 and 7.