Dynamic initiation fracture toughness

In comparison with initiation fracture toughness data, there are substantially fewer data on effects of irradiation on dynamic fracture toughness and crack-arrest toughness. Some early results of vs temperature are shown in Fig. 10.11 (Davidson et al, 1976), while more recent results of Ki are shown in Fig. 10.12 (Iskander et al, 1992). In general, the... 

Fracture toughness, expressed in term of the critical stress intensity factor Kc, was determined at fracture initiation and that point was identified from the load diagram. Although linearity requirements as set out in the protocol were generally satisfied, the identification of the point of fracture initiation from the load diagram was often uncertain because of the difficulty to distinguish small, residual fluctuations in the load signal due to dynamic effects from a pop-in effect. When in doubt about that the test was discarded. 

Some of the more common mechanical properties are provided in Table 10.1 from IAEA (2009). Relative to various measures of toughness, some tests use a blunt notch, while others use a sharp crack to determine material resistance to crack initiation, crack propagation or both, and are conducted under either quasi-static (slow) loading or dynamic (fast) loading conditions. Of all these tests, the Charpy V-notch (CVN) impact test is the most commonly used. In addition to those mechanical properties, there are common reference fracture toughness indices used for RPV steels and many of those are also shown in IAEA (2009). These indices are important because they are used in various ways to normalize fracture toughness of RPV steels. 

The effect of impact velocity, or rather the stress-intensity rate, A (KDynamic fracture toughness, Kj, in partially stabilized zirconia has been observed to increase simply with stress-intensity rate, K, but IQ in SiaN4 initially decreases and then increases with increased K. These specimens were pre-cracked and the same observation that was made for Si3N4 was also made... 

Table 3.1 Room temperature dynamic and quasi-static fracture initiation toughness values of the ceramic materials tested in the present study...

Notch Impact toughness Energy Lateral expansion % shear fracture Dynamic T41J/ Vk, Tq3j, use To,89 mm 7 50% Blunt Charpy V-notch (CVN) impact test e.g., ASTM E 23, EN ISO 148. Obtain curve fit to data vs test temperature, determine various transition temperature indices, e.g., T41J, and upper shelf energy (USE). Initiation and propagation test ... 

---