Crack-arrest toughness test

Iskander S K, Corwin W R and Nanstad R K (1992), Effects of irradiation on crack-arrest toughness of two high-copper welds, pp. 251-269 in Effects of Radiation on Materials 15th International Symposium, ASTM STP1125, R E StoUer, A S Kumar and D S GeUes, eds, American Society for Testing and Materials, Philadelphia, PA. 

ASTM (2013d), Standard Test Method for Determining Plane-Strain Crack-Arrest Fracture Toughness, Kia, of Ferritic Steels, E1221, Annual Book of ASTM Standards, Vol. 03.01, ASTM International, West Conshohocken, PA. 

The CNB test specimen does not require crack length measurement, thereby providing some convenience to the user. However the SEPB and SCF test methods require quality measurements if accurate fracture toughness estimates are expected. For the SEPB test specimen, the precrack front is very difficult to delineate unless it leaves a crack arrest line. An arrest line is easily detected if the crack tip turns out of plane or is hooked, thereby making the precrack and fast fracture plane non-coplanar, as shown in Figure 7. In one study, some cracks were so planar that the front could not be detected with conventional optical microscopy [12]. In such cases, the use of dye penetrants have been successful as shown in Figure 8, however, in some cases penetrants tend to bleed on the fracture surface and the measurements must be made immediately. Dye penetrants must be used with caution as they may cause environmentally assisted crack growth. 

E1221-12a Standard Test Method for Determining Plane-Strain Crack-Arrest Fracture Toughness, of Ferritic Steels... 

The temperature dependence of the fracture toughness for the DGEBA/DDS networks is shown in Fig. 12. Crack growth initiation data are symbolized by the open circles, arrest data by the closed circles, and stable data by the half-filled circles. With the exception of the 1007F/DDS network, the initiation fracture toughnesses increase with the test temperature. In contrast, the arrest values exhibit no noticeable temperature sensitivity, and when observed, the stable fracture toughnesses are of the same magnitude as the arrest values. It is... 

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