PSI - Issue 80

Vaclav Sklenicka et al. / Procedia Structural Integrity 80 (2026) 493–500 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. Stress dependences of (a) the minimum creep rate, ̇ m , and (b) the time to fracture, t f , for different testing temperatures (Open symbols: interrupted exposure data, solid symbols: fractured data). The stress dependences of the strain to fracture, ε f , and the strain to interrupt the creep exposure, t exp , are shown in Fig. 3. It should be noted that at a strain higher than 0.40, the continuation of the creep exposure is limited by the design of the constant-stress creep testing machine used in this study (see 2.2.). Further, at strain ~ 0.40 , an intensive necking due to the instability of the plastic deformation of the alloy matrix occurs, and the final fracture of the tested specimen succeeds very soon. Therefore, we can assume that the values of the strain ε exp are very close to the value of the fracture strain ε f . Similarly, the values of the time t exp should be close to the time to fracture t f .

Fig. 3. Stress dependence of the strain to fracture, ε f , and the strain to interruption of creep test, ε exp . (Open symbols: interrupted exposure data, solid symbols: fractured data).

3.3. Interrelation between creep deformation and fracture processes Several experimental studies on zirconium and zirconium alloys proved that the time to fracture, t f , varies inversely with the minimum creep rate, ̇ m , notably Pahutova et al. (1985), Hayes et al. (2006) and Sklenicka et al. (2021(b)) and others. The relation between the minimum creep rate, ̇ m , and the time to fracture, t f , is frequently described by the generalized form of the Monkman-Grant relationship (Monkman and Grant (1956)) as