PSI - Issue 60

B Shashank Dutt et al. / Procedia Structural Integrity 60 (2024) 690–699 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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From Tables 4-8, it was observed that for many tested conditions, estimated K 1c values and determined fracture toughness ( K j1c ) varied in the range 10-30%. For various steels and titanium alloys, variation of ± 30% in estimation of fracture toughness was observed by Hahn and Rosenfield (1968). Janulionis et al. (2021), used finite element method (FEM) along with tensile properties to estimate J 1c for P91 steels. The estimation of J 1c was carried out for P91 steels in as received condition and after aging treatment. 10% difference between estimated and determined J 1c was observed in the as received condition by Janulionis et al. (2021). For P91 steel after aging, 20% difference between estimated and determined J 1c was observed (Janulionis et al. 2021). Based on observations by Janulionis et al. (2021) and Hahn and Rosenfield (1968), it can be inferred that variation in estimation of fracture resistance up to 30 % is acceptable. In this investigation (Tables 4-7 and Figure 4), it was summarized that the estimation method by Baskes (1975) method is applicable for P91 type of steels. The estimation model by Baskes (1975) is also applicable (Table 8 and Figure 4) for SA 333 type of steel.

4. Conclusions The following are the conclusions of this investigation.

 Stress-strain curves of P91 steel was obtained in temperature range of 300-550 °C. From True stress vs true strain curves, plastic strain energy density was determined. Decrease in strain energy density was observed with increase of test temperatures.  J -R curves were established in the temperature range 300-550 °C and J 1c values were determined. J 1c values were in the range 240-810 kJ.m -2 and equivalent K jc values were in the range 200-420 Mpa.m 0.5 .  An attempt was made to estimate K 1c from tensile properties. The estimated K 1c were within 10-21 % of determined fracture toughness ( K j1c ).  Estimation of K 1c was also carried out for similar P91 steel and SA 333 type of steel. For P91 steel and SA 333 type of steel, estimated K 1c were within 20-30 % of determined fracture toughness values.  The estimation method of fracture resistance due to Baskes is applicable for P91 steels and SA 333 type of steel. References ASTM E8/E8M-16a, 2016, Standard Test Methods for Tension Testing of Metallic Materials, ASTM International, 1-29. ASTM E1820-17a, 2017, Standard Test Method for Measurement of Fracture Toughness, ASTM International, 1-46. Baskes, M.I., 1975. A simplified prediction of K 1c from tensile data. Engineering Fracture Mechanics 7, 249 251. Bhaduri, A.K., Laha, K., 2015. Development of improved materials for structural components of sodium-cooled fast reactors. Procedia Engineering 130, 598-608. Choudhary, B.K., Rao, K.B.S., Mannan, S.L., 1994. Effects of strain rate and temperature on tensile deformation and fracture behaviour of forged thick section 9Cr-1Mo ferritic steel. International Journal of Pressure Vessels and Piping 58, 151-160.