Fracture mechanics specimens

Fracture mechanics specimens (CT, DENT, FNCT, DCB) are a convenient means to study creep behaviour and slow crack growth. 

The same value for scc is observed using fracture mechanics specimens under constant load or in CERTs, provided that similarly sensitized material is used (cf. Figs. 8 and 11). 

The results presented in Fig. 12 are at first sight rather surprising, since standard tests show that the fracture resistance of HIPS and other rubber-modified plastics increases with temperature. The difference between the two types of test lies in the extent of yielding. The fracture mechanics specimens were deseed to produce brittle fracture, with the minimum of yielding crack geometry, tip sharpness, specimen width, and specimen thickness were all chosen accordingly. The resistance to the initiation of brittle fracture follows the trends shown in Fig. 12. On the other hand, ductile fracture resistance increases with temperature, as the yield stress falls. Parvin and Williams measured A/c in 5 mm wide SEN cimens, and found that toughness increased with temperature above —60 °C. 

The effect of cold work on thick plates of Ahoy 600 materials [133,141] was investigated using fracture mechanics specimens. A smaU amount of cold work was found to have a significant effect on crack growth. CCR increases at a high rate in the first 5% of deformation andlevels off with a further increase in cold work. Yield stress increases from 470 to 880 MPa and increases the CCR fourfold [142]. 

Fig. 4.14. Some adhesive joint fracture mechanics specimens, (a) Tapered double cantilever beam (TDCB). (b) Thick double cantilever beam (DCB). (c) Thin double cantilever beam or wedge cleavage specimen, (d) Independently loaded mixed-mode specimen (ILMMS). (e) Scarf joint.

Fracture Mechanics Specimens Constant Strain Rate Polarization-Anodic... 

Design criteria for corrosive environments can be obtained using fracture mechanics specimens. The critical stress intensity for SCC can be determined and is designated Kiscc- Frequently, however, the stress intensity after a predetermined test duration is used as a Kf or final stress intensity rather than monitoring the crack growth to confirm... 

The catastrophic failure of a continuous digester by SCC revealed the need to better understand SCC of steels in alkaline sulfide solutions [118], SCC was subsequently found in many other digesters [181], SCC rates were measured by examination of double cantilever beam fracture mechanics specimens with various stress intensity factors, which were exposed in the failed digester after repairs were made [118],... 

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