PSI - Issue 42

Gauri Mahalle et al. / Procedia Structural Integrity 42 (2022) 570–577 Mahalle et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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Fig 3: Relations between ̇ , τ, and T (a) ln ̇ vs ln( τ ) (b) ln ̇ vs τ (c) ln ̇ vs ln[sinh(ατ)] and (d) ln[sinh(ατ)] vs 1000/T The variation of slopes in Fig 3(a): ln ̇ vs ln( τ ), is represented decrease in the power-law stress exponent from 3.7 at 400 °C to 2.6 at 550 °C. The variation of stress coefficient α in Fig 3(b): ln ̇ vs τ, was observed in the range of 0.2 0.7. The sine-hyperbolic stress exponents (n), is observed in the range of 2.2-3.3 from slopes of lines in Fig 3(c): ln ̇ vs ln[sinh(ατ)] . Finally, the average activation energy Q is evaluated from Eq. (9), by using the average value of n and average line slope in the fig 3(d), observed as 262.33 kJ/mol. Finally, ln(Z) vs. ln[sinh(ατ)] was plot for all SPT test data to validate the hyperbolic function, as given in Fig 4. With a correlation value of 0.9883, fitted line with a slope of n = 2.95 proves a high degree of the linearity. This suggests that a realistic evaluation of the flow stresses can be obtained using the presented constitutive equation.

Fig. 4. plot for ln(Z) vs. ln[sinh(ατ)]

Based on the above analysis, the final modified Arrhenius equation for shear deformation of T91 steel is expressed as: