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Crack arrest transitions

The second part of the investigation was directed toward the understanding of the crack propagation stages. Two questions were especially addressed (i) the determination of the transition from fatigue to brittle fracture (ii) the determination of the crack arrest conditions. Within the frame of linear elastic fracture mechanics, such an analysis requires the... [Pg.59]

The intersection of the crack arrest curve with the yield curve (Curve B) is called the fracture transition elastic (FTE) point. The temperature corresponding to this point is normally about 60°F above the NDT temperature. This temperature is also known as the Reference Temperature - Nil-ductility Transition (RTj dt) is determined in accordance with ASME Section III (1974 edition), NB 2300. The FTE is the temperature above which plastic deformation accompanies all fractures or the highest temperature at which fracture propagation can occur under purely elastic loads. The intersection of the crack arrest curve (Curve D) and the tensile strength or ultimate strength, curve (Curve A) is called the fracture transition plastic (FTP) point. The temperature corresponding with this point is normally about 120°F above the NDT temperature. Above this temperature, only ductile fractures occur. [Pg.140]

VI.ll. The basis for determining the NDTT is the highest temperature at which brittle fracture does not run in the parent material from a brittle weld bead in the standard drop weight test [V1.2]. This can be thought of as the bottom of the transition temperature curve either for propagation/crack arrest or for dynamic initiation from small initial cracks. [Pg.331]

Key words fracture toughness, J-integral, master curve, irradiation, crack-arrest, embrittlement, Charpy impact, nil-ductility transition (NDT) temperature, pressurized water reactor (PWR). [Pg.295]

These observations can be explained on the basis of the weak interface in the transition zone (porous layer in Figure 2.5) and the Cook-Gordon crack arrest mechanism [82] shown in Figure 3.40. The stress field ahead of the elliptical crack tip consists ofthe familiar stress concentration profile in the direction of the external tensile stress (/direction), and a tensile stress field in the... [Pg.90]

Initial Crack Generated Adiabatically. Below 160 K, only uncontrolled crack propagation is possible, at a velocity roughly one-third of the velocity of sound. The tip zone is heated adiabatically. The difference is a moving crack tip which involves different thermal conditions (18,19). If the temperature rises far enough to exceed brittle-plastic transition, the tip zone becomes plastic and stress relaxation can take place (20,21). When this initial crack no longer grows, the condition is kept frozen in an arrest zone, where Kic can be measured. [Pg.152]


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