PSI - Issue 71

A. Syed et al. / Procedia Structural Integrity 71 (2025) 82–89

89

specimens tested at 25 °C and 300 °C, respectively. It indicates that the crack initiation toughness is lower at room temperature than at 300 °C. The observed increase at 300 ˚C is consistent with enhanced ductility and reduced yield strength at elevated temperatures leading to greater plastic energy dissipation before crack propagation. There is a reducing slope of JR curve at higher crack growth, indicating saturation in the amount of energy required for increment in the crack growth value. 6. Conclusions Tests were carried out at different temperature to evaluate the fracture toughness of Zircaloy-4 material. Finite element analysis has been carried out to determine the friction coefficient and stress triaxiality values. Following conclusions can be drawn from the study. ● Conical mandrel technique can be used for determination of crack initiation and propagation toughness of thin tubular cracked specimens. ● The load-displacement response at different temperature consists of majorly two distinct slopes. The initial slope occurs due to overcoming of friction between the mandrel and specimen however, it gets increased to higher values due to more opening of the specimen after a particular displacement. ● The change in slope of the load-displacement curve occurs at 12 mm and 16 mm for specimens tested at 25 °C and 300 °C, respectively. This indicates a slower crack initiation for specimen tested at higher temperatures. ● Good agreement between the FE results and experimental data of load displacement occurs upto a particular displacement, after which it deviates due to no crack growth modelling in the FE software. ● The triaxiality at the crack tip is 0.77 at 300 °C, while it increases to 0.8 at 25 °C. This suggests lower crack initiation toughness at lower temperatures due to higher stress triaxiality conditions. ● The coefficient of friction is 0.1 for specimen tested at 25 °C which gets increased to 0.14 when the temperature is increased to 300 °C. ● The crack initiation toughness is found to be 105 kJ/m 2 at 25 °C and it value increases to 182 kJ/m 2 at 300 °C. References Bajaj, S.S., Gore, A.R., 2006. The Indian PHWR. Nuclear Engineering and Design 236: 701-722. Bertolino, G., Meyer, G., Perez, I.J., 2003. In-situ crack growth observation and fracture toughness measurement of hydrogen charged zircaloy-4. Journal of Nuclear Materials 322: 57-65. Dodds, R.H., Shih, J.C.F., Anderson, T.L., 1993. Continuum and micromechanics treatment of constraint in fracture, Int. J. Fract. 64, 101 – 133. Foster, J.P., Leasure, R.A., 1989. Simulated fuel expansion testing of Zircaloy tubing. Van Swan, L.F.P., Eucken, C.M. 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