PSI - Issue 60

P.K. Sharma et al. / Procedia Structural Integrity 60 (2024) 335–344 P.K. Sharma/ Structural Integrity Procedia 00 (2023) 000 – 000

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when the temperature increases from 700°C to 800°C. The displacement at which the maximum load occurs decreases from room temperature to 700°C and then, increases at 800°C. This indicates crack initiation and propagation becomes faster when temperature is increased from room temperature to 700°C. Rapid drop in load carrying capacity of the material is observed at 700°C as compared to other temperature indicating faster crack propagation with increase in load-line displacement. This peculiar behavior in load-displacement behavior in this temperature range is due to the presence of brittle phases near to the crack-tip. This also indicates lower fracture resistance in this temperature range. At 800°C, there is no rapid drop in load upto displacement of 4 mm indicating improvement in fracture behavior at temperature above 700°C. 3.2. Variation of ductile crack growth at different temperature In order to compare the extent of crack growth in the SENT specimen at each test temperature, the crack growth data as a function of temperature and applied displacement has been plotted in Fig. 4. It can be observed that the crack growth is faster at 700°C indicating lower resistance to fracture. Maximum crack growth of 6 mm is observed at 700°C at a load-line displacement of 2.3 mm. The crack growth is slowest at 800°C with 6 mm crack length at a load-line displacement of 5 mm indicating improvement in fracture resistance after 700°C. This data is subsequently used for evaluation of J-integral of alloy 690 material.

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Fig. 3: Comparison of load-displacement curves of SENT specimen at different temperature.

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Fig. 4: Crack growth as measured from fracture experiments as a function of applied displacements at different temperature.